1. 拉尼娜状态的基本定义与分类
1.1 拉尼娜的核心定义与ENSO框架定位
拉尼娜（La Niña），意为“小女孩”，是厄尔尼诺-南方涛动（ENSO）循环中的冷相位，与暖相位厄尔尼诺（El Niño）相对。ENSO是全球最强的年际气候变率信号，由赤道太平洋海表温度（SST）、大气环流和海洋次表层温度的周期性波动构成 1。拉尼娜状态的本质特征是赤道中东太平洋海表温度持续异常偏冷。
判定拉尼娜事件发生的主要指标是NINO3.4区域（5°N-5°S, 120°-170°W）的月平均海表温度异常。当该区域的SST距平值连续至少5个重叠的3个月平均值（例如，DJF、JFM、FMA等）低于或等于-0.5°C时，即认为发生了一次拉尼娜事件。这一标准由美国国家海洋和大气管理局（NOAA）等机构广泛采用。在ENSO循环中，拉尼娜通常伴随着赤道太平洋信风异常增强、太平洋沃克环流加强以及印尼地区对流活动增强等大气响应。它在全球气候系统中扮演着关键角色，通过海气耦合作用影响着全球各地的天气模式和气候异常 1。拉尼娜与厄尔尼诺事件交替出现，共同构成ENSO的完整循环，对全球气候预测具有重要意义 1。
1.2 拉尼娜的类型划分与典型特征
拉尼娜事件根据其持续时间和强度可以进行分类，其中最主要的区分是单年拉尼娜和连续拉尼娜。单年拉尼娜指事件在一年内发生并消退，而连续拉尼娜，也被称为“多年度拉尼娜”或“三重拉尼娜”（Triple-dip La Niña），则表示事件持续两年或更长时间。例如，2020年至2022年的“三重拉尼娜”事件，导致了韩国历史上最严重的森林火灾等灾害 2。
连续拉尼娜与单年拉尼娜在海表温度异常强度、持续时间及其对全球气候的环流响应上存在显著差异。连续拉尼娜事件通常具有更广阔的子午向信风增强范围，这导致赤道太平洋的热量再充电过程减缓，从而使得冷异常得以持续，对全球气候、生态系统和农业产生更长时间的影响 3。相较于单年事件，连续拉尼娜事件可能在次年持续其冷异常，这种现象在全球变暖背景下有增加的趋势。有研究表明，在全球温室气体排放情景下，连续拉尼娜事件的发生频率在低排放情景下可能增加19%±11%，在高排放情景下可能增加33%±13% 3。
历史案例显示，连续拉尼娜事件对全球范围内的极端天气和气候灾害具有放大效应。例如，与拉尼娜事件同时发生的流感疫情强度和严重程度更高 4。此外，拉尼娜事件还会导致一些区域（如南美中西部）出现与干旱相关的缺水问题，影响灌溉用水供应 5。在印度洋，季风前热带气旋活动也与拉尼娜现象有关 6。由于连续拉尼娜事件的持续性影响，它们在气候预测和灾害预防中占据了更为重要的地位，尤其是在全球变暖的背景下，理解其形成机制和未来变化趋势变得尤为关键 3。
2. 拉尼娜的形成机制与驱动因素
2.1 海洋-大气耦合的核心过程
拉尼娜的形成是一个复杂的海气耦合过程，涉及赤道太平洋海洋和大气之间的正反馈循环。其核心机制可以概括为以下几个方面：
首先，信风的增强是拉尼娜形成和维持的关键驱动力之一。在拉尼娜事件期间，赤道太平洋上空的东风信风异常增强。这些增强的信风将太平洋表层温暖的海水向西吹送，导致赤道东太平洋的暖水堆积减少，表层冷水上升补偿，从而使该区域海表温度进一步降低。这种SST的降低反过来又进一步加强了海气压差，驱动信风进一步增强，形成一个正反馈循环。
其次，赤道太平洋温跃层的变化也扮演着重要角色。温跃层是指海洋中温度随深度快速变化的层，其深度和坡度对SST有显著影响。在拉尼娜条件下，增强的信风使得赤道太平洋的温跃层在东太平洋地区变浅，而在西太平洋地区加深。温跃层在东太平洋的变浅，使得深层冷水更容易通过上升流到达表层，进一步加剧了海表温度的下降。同时，温跃层的这种东西向坡度变化，即“热含量倾斜”，使得东太平洋的冷水可以持续地影响表层温度，例如，研究表明温跃层温度在西赤道太平洋具有半岁差周期，这暗示了热带温跃层在轨道尺度的气候变化中发挥决定性作用 7。深层温跃层混合事件，特别是在热带不稳定波（TIWs）和赤道潜流（EUC）的剪切作用下，在拉尼娜条件下发生得更频繁和更深入，这进一步加强了温跃层的冷却效应 8。
伴随温跃层变浅和信风增强，赤道冷舌的扩展是拉尼娜的另一个显著特征。赤道冷舌是赤道东太平洋由上升流形成的冷水区域。在拉尼娜期间，由于信风增强和温跃层变浅，冷舌的范围和强度都会显著扩大和增强，使得赤道中东太平洋的冷异常更为显著。
最后，沃克环流的异常增强是大气对海洋冷异常的反馈机制。沃克环流是赤道太平洋上空的一个大气环流圈，其上升支位于西太平洋暖池区，下降支位于东太平洋冷水区。研究表明，在拉尼娜事件中，当沃克环流增强时，会形成一种拉尼娜型的环流 9。这种加强的沃克环流，通过增强东风信风和影响海洋动力学，维持并放大了赤道太平洋的冷异常，从而巩固了拉尼娜状态。近地表铍-7浓度模式的分析也显示，在拉尼娜事件中，赤道太平洋区域的铍-7浓度会呈现显著的模式，这与沃克环流的相应状态有关 10。
2.2 外部强迫与内部变率的影响
除了海气耦合的内部动力学机制外，拉尼娜的形成和发展也受到外部强迫和内部变率的显著影响。其中，全球变暖背景下的平均态变化以及特定区域的海表温度异常，对拉尼娜事件的调制作用尤为重要。
全球变暖导致的气候平均态变化，尤其是海洋热量收支的调整，被认为是影响ENSO循环和拉尼娜事件未来趋势的关键因素。例如，有研究指出，副热带东北太平洋（Subtropical Northeast Pacific, SNP）的增温极值对拉尼娜的持续性具有强化作用 3。在温室气体增暖情景下，SNP区域的平均态增暖最大值会增强该区域对扰动的热力学响应，进而生成比20世纪更偏北的异常东风，响应于厄尔尼诺的暖异常。这种向北扩展的东风异常模式所伴随的较慢的热量再充电过程，使得第一年的拉尼娜冷异常更容易持续到第二年，从而促使连续拉尼娜事件的发生频率增加 3。
此外，北热带大西洋（North Tropical Atlantic, NTA）和SNP区域海表温度的早期变化，也被认为是触发ENSO事件（包括拉尼娜）的前兆因素 11。虽然以往研究多单独考察这些前兆因素的影响，但它们之间的联合作用与单独影响显著不同。在全球变暖背景下，NTA和SNP对ENSO的影响均显著增强，且这种增强程度紧密相关。赤道外东太平洋更湿润的平均态是控制NTA和SNP对ENSO影响的单一贡献因素 11。这意味着全球变暖不仅可能通过改变ENSO事件的平均强度和频率，还可能通过调节这些关键前兆区域的海温，来影响拉尼娜事件的发生和演变。
海洋内部变率，如与ENSO循环相位转换相关的海洋热量累积和释放过程，也对拉尼娜事件的持续和强度有重要贡献。例如，拉尼娜事件通常在厄尔尼诺事件之后发展，且持续时间往往更长 3。这表明ENSO循环中的前一个相位对其后一个相位的演变具有预设作用。在拉尼娜期间，上对流层水汽含量呈现负异常，这与全球变暖和ENSO对流层水汽的影响一致，其中ENSO可以解释水汽年际变化的61% 12。这种水汽的异常变化也反映了海气耦合系统内部的复杂反馈过程。
综上所述，拉尼娜的形成和驱动不仅是赤道太平洋内部海气相互作用的结果，更是全球变暖背景下外部强迫与ENSO系统内部变率复杂协同作用的体现。全球变暖导致的平均态变化，特别是副热带海温增温极值，可能通过调制大气遥相关和海洋热量收支，增加连续拉尼娜事件的频率和强度，进而对全球气候产生更深远的影响 3。
3. 拉尼娜的气候表现与全球遥相关
3.1 赤道太平洋的局地气候响应
拉尼娜事件期间，赤道太平洋地区表现出与厄尔尼诺事件截然相反的局地气候特征，这些特征是其全球遥相关影响的基础。最核心的局地气候响应体现在赤道中东太平洋海表温度（SST）的持续冷异常。根据定义，NINO3.4区域（5°N-5°S, 120°-170°W）的SST距平值持续低于-0.5°C是判定拉尼娜的标准之一。这种冷异常在东太平洋尤为显著，导致该区域水温低于正常水平。
与SST冷异常密切相关的是对流活动的抑制。在正常年份，赤道西太平洋由于暖池的存在，是全球对流活动最活跃的区域之一。然而，在拉尼娜期间，由于东太平洋冷水上升流增强，西太平洋的暖水被推向更西方，赤道中东太平洋的SST降低，使得该区域大气对流活动显著减弱。这种对流活动的抑制减少了垂直运动，进而影响了云的形成和降水分布。
同时，赤道西风的减弱或东风信风的异常增强是拉尼娜的另一个标志性特征。增强的信风将表层暖水向西太平洋堆积，使得赤道中东太平洋的温跃层变浅，深层冷水更容易上涌。这种信风的异常增强与海表温度的降低形成正反馈，进一步维持和强化了拉尼娜状态。
对比厄尔尼诺事件，拉尼娜的局地气候差异体现在：厄尔尼诺表现为赤道中东太平洋海表温度异常偏暖，对流活动增强，赤道西风异常增强或信风减弱。例如，在厄尔尼诺期间，通常会导致该区域上层对流层西风增强以及副热带急流向南移动 13。而拉尼娜则完全相反，赤道中东太平洋海温偏冷，对流抑制，信风增强。这种对比鲜明的局地气候响应是理解ENSO循环及其对全球气候影响的关键。这些局地变化通过海气耦合作用，最终通过大气遥相关模式，将影响传播到全球各地。
3.2 全球气候遥相关模式
拉尼娜事件通过复杂的大气遥相关模式，将赤道太平洋的局地气候异常传播至全球，引发全球范围内不同区域的气候响应。这些遥相关模式主要包括太平洋-北美型（PNA）波列和热带-副热带波列等。
在拉尼娜期间，由于赤道中东太平洋海表温度偏冷和对流活动抑制，导致沃克环流异常增强，这种大气环流的改变触发了一系列罗斯贝波（Rossby waves），这些波列沿着大气波导传播，影响全球各地的气候。例如，在南半球，特别是澳大利亚春季，拉尼娜事件会从太平洋中部产生一个清晰的波列，与厄尔尼诺期间起源于澳大利亚附近的波列形成对比 14。
具体的全球气候遥相关模式和区域气候异常表现如下：
东南亚/澳大利亚多雨：拉尼娜期间，太平洋西部的暖水异常和增强的对流活动导致该区域降水显著增加。这使得东南亚和澳大利亚北部，尤其是澳大利亚西北部，经常经历高于平均水平的降雨量，甚至引发洪涝灾害。例如，在西北澳大利亚，强拉尼娜年通常与鱼类、树木和珊瑚的生长呈正相关，表明降雨量增加对这些生态系统有利 15。印度尼西亚的热带泥炭沼泽森林，在拉尼娜期间也可能面临不同的蒸散量，这与降水和水分条件密切相关 16。
南美南部干旱：拉尼娜事件通常导致南美洲中西部地区，特别是阿根廷中西部和智利中部，出现严重的干旱，从而影响水资源供应和农业灌溉 5。巴西的亚马逊盆地在周期性拉尼娜事件与印度洋偶极子模式和热带北大西洋增暖的耦合下，也可能经历极端干旱 17。此外，南美南部的针叶树种，其繁殖周期可能与强拉尼娜带来的干旱密切相关 18。
非洲南部洪水：虽然未在提供的资料中直接提及非洲南部的洪水案例，但拉尼娜通常通过改变全球大气环流模式，可能导致非洲部分地区降水异常。例如，与拉尼娜事件相关的降水异常，会影响到一些虫媒传染病（如疟疾、登革热）的传播，表明其对区域气候和公共卫生的影响深远 19。
北美地区影响：拉尼娜也会对北美气候产生显著影响。例如，拉尼娜通常与北美西北部的冬季降温以及美国南部持续干旱有关 20。对于北美西南部而言，拉尼娜式响应可能导致更严重的干旱情景 21。
其他区域影响：在哥伦比亚，拉尼娜事件通常导致降雨量增加，使得钩端螺旋体病病例增加25% 22。西北太平洋的霓虹飞乌贼（Neon flying squid）栖息地质量与ENSO诱导的海洋条件变化密切相关，拉尼娜事件往往能带来更好的栖息条件和渔获量 23。在长江流域，拉尼娜事件还会通过影响气温和降雨量，增加细菌性痢疾的风险 24。在青藏高原，拉尼娜事件期间，特别是西北部地区，降雨侵蚀力可能更为严重 25。此外，拉尼娜事件还会导致夏威夷群岛信天翁保护区（French Frigate Shoals）的海洋垃圾沉积量显著少于厄尔尼诺事件 26。
这些遥相关模式表明，拉尼娜不仅仅是赤道太平洋的区域现象，而是能够通过大气环流的全球性调整，对世界各地的天气和气候产生广泛而深远的影响，包括降水、温度、极端事件频率等。因此，理解和预测拉尼娜事件对于全球范围内的灾害预防和资源管理至关重要。
4. 拉尼娜对生态系统的多维度影响
4.1 海洋生态系统响应
拉尼娜事件通过改变海表温度、洋流模式和初级生产力，对全球海洋生态系统产生多维度且复杂的影响。这些影响可以体现在珊瑚礁、鱼类分布以及浮游生物群落结构等多个层面。
珊瑚礁白化与恢复：尽管厄尔尼诺通常与大规模珊瑚白化事件紧密相关，但拉尼娜事件同样能对珊瑚礁造成影响。例如，在2020年，南中国海的珊瑚礁经历了严重的急性热应力异常，导致白化事件，其中拉尼娜事件也参与其中 27。在某些特定区域，如加拉帕戈斯群岛的恶魔冠（Devil's Crown）标志性鹿角珊瑚礁，甚至在拉尼娜冷却事件期间也经历了严重的死亡，尽管该区域在此前和之后都表现出快速恢复 28。这表明，即使是冷却事件，如果温度异常显著或与当地生态系统阈值不符，也可能对珊瑚造成压力。此外，拉尼娜与中太平洋涛动（PDO）的负相位异步时，可能导致年度海表温度（SST）峰值，进而引发珊瑚白化和珊瑚覆盖率下降 29。这凸显了ENSO事件与低频气候变率协同作用的复杂性，以及它们对珊瑚礁健康的潜在威胁。
鱼类分布与丰度变化：拉尼娜对鱼类群落的影响尤为显著。在北海湾（Beibu Gulf），强拉尼娜事件影响了鱼类群落的组成、丰度和分布，特别是日本鲭鱼（Japanese jack mackerel）和日本竹荚鱼（Japanese scad）等小型远洋鱼类的丰度和分布受影响最大，其种群丰度与海表盐度、海表温度密切相关 30。在哥斯达黎加的可可岛，研究发现扇形锤头鲨（Sphyrna lewini）和双髻鲨（Galeocerdo cuvier）在拉尼娜事件期间被发现的频率更高，而它们的丰度在厄尔尼诺期间则显著下降，表明拉尼娜条件对其有利 31。同样，在澳大利亚的宁加洛礁（Ningaloo Reef），幼年裸颊鲷（lethrinids）的年度丰度在拉尼娜年份达到峰值，这些年份海水更温暖，洋流更强劲 32。此外，在东南太平洋中部，拉尼娜事件被认为在生物学上对光滑锤头鲨（Sphyrna zygaena）种群有利，导致其生物量增加 33。这些案例表明，拉尼娜可能通过改变水温、盐度、洋流以及食物链可获得性，对不同鱼种的分布和繁殖产生正面或负面影响。对于高度移动的远洋捕食者，如黑马林（black marlin），拉尼娜事件期间其适宜栖息地甚至可以向南延伸约300公里 34。
浮游生物群落结构调整：作为海洋食物网的基础，浮游生物对拉尼娜事件的响应也至关重要。墨西哥湾北部地区，强烈的河流径流和营养物质输入，使得该地区拥有高产的沿海生态系统。研究表明，ENSO是该地区冬季和春季盐度和浮游生物生物量年际变化的主要驱动因素，其中厄尔尼诺和拉尼娜的影响存在显著不对称性，厄尔尼诺条件下的影响幅度更大、范围更广 35。在加拉帕戈斯群岛，赤道潜流（EUC）对富营养水的输送支持了浮游植物的初级生产力。尽管在厄尔尼诺期间营养供应受到抑制，但在拉尼娜事件期间，由于混合层和深水层之间的分层增加，特别是在东部站位，营养水平并未显著增强 36。在巴西东北部的热带水库中，拉尼娜导致的异常降雨量显著改变了浮游植物群落的形态功能群（MBFG）结构，导致蓝藻物种多样性的降低和浮游植物总多样性的增加，这与水体混合和营养脉冲有关 37。这表明拉尼娜通过影响水体营养盐、温度和水文条件，重塑了浮游生物群落的组成和生产力。
其他海洋生态影响：除了上述方面，拉尼娜事件还可能影响其他海洋生物和生态过程。例如，南极洲西部半岛的冰川融化扰动，会使海底生态系统从净自养性转向净异养性，而暖拉尼娜春季（2016年）由于冰川融水径流增加导致的混浊水体限制了海底微藻的生产，加速了这种转变 38。在加拉帕戈斯群岛，反复的ENSO温度异常可能导致有孔虫密度较低，而拉尼娜异常所带来的慢性高营养和低pH值则可能抑制其在厄尔尼诺后的恢复，并导致南部群岛有孔虫群落以异养为主 39。在澳大利亚西部的班伯里沿海，拉尼娜事件期间海豚丰度较低，这可能与海洋环境变化影响了海豚的猎物分布有关 40。这些例子共同揭示了拉尼娜事件对海洋生态系统从微观到宏观，从热带到极地的广泛而深刻的影响。
4.2 陆地生态系统扰动
拉尼娜事件通过引发全球性的降水异常和温度变化，对陆地生态系统造成显著扰动，影响植被生长、物种分布以及食物链结构，甚至对人类社会产生间接影响。
植被生长与生产力变化：拉尼娜导致的降水异常是影响陆地植被的关键因素。在一些区域，拉尼娜带来的降雨增加促进了植被生长。例如，印度季风降雨（ISMR）和植被动态受到ENSO的显著影响，拉尼娜年份印度哈里亚纳邦的降雨量和归一化植被指数（NDVI）均高于平均水平 41。类似地，印度大部分地区（Kharif季节82.82%，Rabi季节80.95%）在长期内呈现NDVI正增长趋势，这与拉尼娜期间的有利降水条件有关 42。在西北澳大利亚，强拉尼娜年通常与鱼类、树木和珊瑚的生长呈正相关，表明降雨量增加对这些生态系统有利。然而，在另一些区域，拉尼娜可能导致干旱，从而抑制植被生长。例如，亚马逊地区的黑水和白水洪泛平原的Macrolobium acaciifolium树木生长模式与马瑙斯港记录的水位变化显著相关；厄尔尼诺事件导致降水异常减少，河流径流降低，陆地阶段延长，从而促进了树木生长，但拉尼娜事件的气候信号在树木年代学代理中并不明显 43。这说明，拉尼娜对植被的影响具有区域异质性，取决于当地的降水响应。此外，东非地区的植被变化也受到热带太平洋和印度洋海表温度的综合影响，拉尼娜期间更湿润的条件导致植被逐渐恢复 44。
寄生虫传播与食物链结构扰动：拉尼娜事件改变的环境条件能够间接影响寄生虫的传播，进而扰动陆地生态系统的食物链结构。在墨西哥阿卡普尔科湾，研究发现太平洋石首鱼（Lutjanus inermis）肠道寄生虫群落的组成和结构在厄尔尼诺和拉尼娜等异常气候事件期间表现出显著的年际变化 45。气候事件可能通过影响局部食物网结构，间接改变肠道寄生虫物种的传播率。例如，宿主捕食行为的变化或宿主种群的增减可能导致寄生虫负荷的波动 45。在哥伦比亚，拉尼娜导致的降雨增加使得钩端螺旋体病病例增加了25%，这是一种通过受感染动物尿液传播的细菌性疾病，表明气候变化与疾病传播之间的复杂联系。此外，赞比亚裂谷热（Rift Valley fever, RVF）的暴发与异常降水（拉尼娜）存在正相关 46。这表明拉尼娜通过影响降水模式、宿主行为和种群动态，对陆地生物多样性和疾病生态学产生深远影响。
农业活动与人类文明影响：拉尼娜对陆地植被的影响也直接关系到人类的农业生产和食物安全。在墨西哥尤卡坦半岛，玛雅文明时期玉米种植地的重建数据揭示了其与厄尔尼诺-南方涛动（ENSO）变率之间的关系，这暗示了气候波动对古代农业社会的重要性。尽管直接提及拉尼娜对玛雅玉米种植的具体影响较少，但ENSO的整体效应，包括拉尼娜带来的降水变化，无疑会对依赖雨水灌溉的农作物产生关键影响。在亚马逊流域，拉尼娜事件可能会导致极端干旱，特别是在与印度洋偶极子和热带北大西洋增暖耦合时，这会影响森林的健康和农业生产。
总而言之，拉尼娜通过改变区域降水和温度模式，直接影响植被的生长和生产力，从而重塑陆地生态系统的结构和功能。同时，这些环境变化也间接影响寄生虫的传播和疾病生态，甚至对人类的农业活动和粮食安全构成挑战。
5. 拉尼娜对人类活动与公共健康的影响
5.1 农业与水资源管理挑战
拉尼娜事件通过其对全球降水模式的显著影响，对农业生产、水资源管理和粮食安全构成了严峻的挑战。其导致的区域性干旱或洪涝，直接冲击着依赖气候条件的农业系统和水资源供应。
对农业生产的影响：
拉尼娜事件可以显著改变农业地区的降水和温度条件，从而影响作物产量和牲畜健康。
- 印度季风降水异常：拉尼娜与印度夏季风降水（ISMR）的增强密切相关，这对于印度农业至关重要。虽然增强的季风降水通常有利于水稻等作物的生长，但如果降水过多或分布不均，也可能导致洪涝灾害，损害农作物。相反，一些研究指出，厄尔尼诺事件会对哥伦比亚的菜豆产量产生负面影响，而拉尼娜事件则没有显著的负面影响，这表明不同作物和区域对ENSO事件的响应存在差异 47。
- 寄生虫传播对牲畜的影响：拉尼娜导致的降水变化也间接影响畜牧业。例如，在非洲南部，ENSO对小型反刍动物寄生虫（如捻转血矛线虫）的传播潜力有显著影响。强拉尼娜事件能增加热带农生态区这些寄生虫的传播潜力，尤其是在从厄尔尼诺向拉尼娜过渡的时期，这会增加牲畜的疾病风险，影响农业生产 48。
- 粮食安全与作物多样性：在秘鲁亚马逊地区，2011-2012年严重的拉尼娜事件导致了大规模洪水和临时人口迁移。该地区的儿童饮食模式和多样性受到影响，谷物、大米、奶制品和糖的摄入频率减少，而香蕉的摄入量增加，表明气候事件迫使当地居民改变饮食结构以适应环境变化。此外，拉尼娜条件显著降低了饮食多样性 49。这突显了在面对气候变化时，需要通过适应性措施（如气候和性别敏感的公共卫生营养计划）来保障脆弱人群的饮食安全。
对水资源管理的影响：
拉尼娜在全球范围内的降水异常对水资源的供应和管理产生了深远影响，尤其是在水资源已经紧张的地区。
- 干旱与水短缺：在南美洲中西部，特别是阿根廷中西部和智利中部，拉尼娜事件导致的干旱严重限制了水资源供应和农业灌溉需求 5。这种长期的干旱使得这些地区面临严重的水资源危机，对当地的农业和居民生活造成巨大压力。
- 水库水量变化：在巴西东北部，拉尼娜年份通常与降水正异常相关，导致水库蓄水量增加。然而，厄尔尼诺年份则导致负降水异常和水库水量减少 50。这表明，拉尼娜能够为某些干旱地区带来缓解，但也要求水资源管理者做好洪涝和水库调度准备。
- 蒸散发和水文模型：精确的蒸散发（ET）估算对于流域尺度的农业干旱监测和灌溉规划至关重要。在印度东部的Kangsabati河流域，拉尼娜事件能够更好地重现流域尺度的径流和ET通量，这对于改进水文模型、提升干旱监测准确性具有重要意义 51。
- 水质问题：在图瓦卢等南太平洋岛国，2011年由强拉尼娜引起的严重干旱紧急情况，导致腹泻爆发。研究发现，家庭水箱水位低于20%以及洗手频率降低是导致腹泻风险增加的独立因素 52。这表明在拉尼娜导致的干旱条件下，水资源短缺可能引发水质恶化，从而带来公共健康风险。
应对策略需求：
面对拉尼娜带来的农业和水资源管理挑战，各国和地区需要制定综合性的应对策略。这包括：
- 早期预警系统：利用气候预测模型，提前预警拉尼娜事件的发生及其可能带来的降水异常，为农业生产和水资源调度提供决策依据。
- 气候适应性农业：推广耐旱或耐涝作物，改进灌溉技术，发展多样化的农业种植模式，以提高农业系统对气候变化的韧性 53。
- 综合水资源管理：建立健全的水资源监测和管理系统，优化水库调度，推广节水技术，并投资建设基础设施以提高水资源的收集、储存和分配效率。
- 跨部门合作：加强气象、农业、水利和公共卫生部门之间的合作，共同应对拉尼娜带来的多重挑战。
5.2 极端天气与公共健康风险
拉尼娜事件通过引发全球范围内的极端天气，如异常降水、高温、干旱或洪涝，对人类公共健康构成严重威胁。这些极端天气事件不仅直接导致伤害和死亡，还会通过影响环境条件、病媒生物活动以及社会经济因素，间接加剧疾病的传播和健康风险，尤其对脆弱人群影响更为显著。
异常降水与传染病风险：
拉尼娜事件通常伴随着特定地区降水量的显著变化，这与多种传染病的发生和传播密切相关：
- 肠道疾病：极端降水事件（如暴雨和洪水）可能导致水源污染，从而增加肠道疾病的风险。例如，在马里兰州的沿海地区，极端降水事件每增加一天，弯曲杆菌病（campylobacteriosis）的风险就增加3% 54。值得注意的是，这种风险在拉尼娜时期显著更高，每增加一天极端降水事件，弯曲杆菌病风险增加9% 54。同样，在印度的艾哈迈达巴德，极端降水事件与肠热病（Enteric Fever）风险增加5%相关 55。在太平洋岛国图瓦卢，2011年由强拉尼娜引起的严重干旱紧急情况导致腹泻爆发，主要原因是家庭水箱水位过低和洗手频率降低，表明极端干旱同样会通过影响水质和卫生习惯，增加肠道疾病风险。
- 蚊媒传染病：拉尼娜对降水的影响会直接改变蚊媒的繁殖环境，从而影响登革热、基孔肯雅热、寨卡病毒和疟疾等疾病的传播。
- 登革热：在泰国中部，拉尼娜事件与登革热发病率和风险水平的增加有关 56。所罗门群岛的研究也显示，拉尼娜与瓜达尔卡纳尔省登革热样疾病（DLI）风险增加4.5倍相关，而厄尔尼诺则与风险降低相关 57。在巴西托坎廷斯州，拉尼娜与2010-2012年间的登革热感染相关 58。气候变化与更频繁、更强烈的ENSO事件相关，预示着登革热等新发传染病的发病频率和严重程度可能增加 4。
- 疟疾：虽然气候变化对疟疾的影响复杂且存在区域差异，但一些研究指出拉尼娜与疟疾传播有关。例如，在南非林波波省，拉尼娜与季前高发疟疾有关 59。在埃塞俄比亚，尽管疟疾疫情与ENSO关联复杂，但普遍认为拉尼娜事件会带来特定的降雨和温度模式，可能影响疟疾传播 60。在委内瑞拉东北部，1988年的拉尼娜事件导致疟疾传播达到异常高水平 61。然而，也有研究显示，在东非之角等地区，温暖的厄尔尼诺南方涛动（ENSO）与裂谷热、霍乱和疟疾的更高风险相关，而拉尼娜事件期间则与登革热、基孔肯雅热和黄热病相关 4。这表明ENSO对蚊媒疾病的影响具有显著的地理特异性。
- 其他虫媒传染病：拉尼娜事件可能通过影响局地生态系统，改变昆虫传播疾病的宿主和病原体的地理分布 62。
高温与健康风险：
尽管拉尼娜通常与赤道太平洋冷异常相关，但其遥相关效应可能导致其他地区出现异常高温。
- 心血管和呼吸道疾病：极端高温事件对心血管和呼吸道疾病患者构成额外负担，可能加重心脏病、中风和哮喘等疾病的症状，甚至增加死亡风险。例如，在拉尼娜期间，极端高温事件也可能增加弯曲杆菌病风险 54。
- 传染病传播：高温还可以加速病原体的繁殖和病媒生物的生长周期，从而增加虫媒传染病的传播效率。
脆弱人群的健康风险放大效应：
拉尼娜事件及其带来的极端天气对脆弱人群的健康影响尤为严重。
- 老年人、儿童和慢性病患者：这些群体通常对温度变化和疾病的抵抗力较弱。例如，高温可能导致老年人中暑和脱水，儿童更容易感染肠道疾病。
- 低收入和边缘化社区：这些社区往往居住在更容易受到洪水、干旱和污染影响的区域，并且获得清洁水、卫生设施和医疗保健服务的机会有限。他们的住房条件可能较差，抵御极端天气的能力不足，在灾害发生时面临更高的健康风险。例如，图瓦卢的干旱和腹泻爆发对当地社区，特别是儿童的饮食和健康造成了显著影响。
- 粮食不安全人口：拉尼娜导致的农业歉收和水资源短缺，直接威胁到粮食安全，使得本就食物不足的人口面临更严重的营养不良问题，从而降低其对疾病的抵抗力。
综上所述，拉尼娜事件通过引发复杂的极端天气模式，对全球公共健康构成多方面挑战。其对传染病传播的促进作用，以及对脆弱人群健康风险的放大效应，凸显了在气候变化背景下，加强疾病监测、预警系统建设以及制定适应性公共卫生策略的紧迫性。
6. 拉尼娜的未来变化趋势与预测挑战
6.1 全球变暖下的趋势预估
在全球变暖背景下，拉尼娜事件的未来变化趋势，特别是连续拉尼娜事件的频率和强度，是气候科学界关注的焦点。气候模型预估显示，21世纪连续拉尼娜事件的发生频率可能显著增加，这将对全球气候、生态系统和人类社会产生深远影响。
连续拉尼娜事件频率的增加：
基于气候模型的模拟结果，有研究指出，在全球温室气体排放情景下，连续拉尼娜事件的发生频率将呈上升趋势。具体而言，在低排放情景下，连续拉尼娜事件的频率可能增加19%±11%；而在高排放情景下，这一增幅可能达到33%±13% 3。这种增幅在更高排放情景下，模型间的一致性更强。这意味着，随着全球变暖的加剧，我们可能会更频繁地经历持续两年或更长时间的拉尼娜事件，从而导致与拉尼娜相关的气候极端事件（如干旱、洪涝）发生频率和持续时间的增加 3。
副热带海温增温极值对拉尼娜持续性的强化作用：
全球变暖不仅仅是全球平均温度的升高，它还在区域尺度上改变着海洋的温度分布，特别是副热带海域的增温极值对拉尼娜的持续性发挥着关键的调制作用。
- 副热带东北太平洋（SNP）的增温效应：研究发现，在全球变暖背景下，副热带东北太平洋（Subtropical Northeast Pacific, SNP）的平均态增暖最大值会增强该区域对扰动的热力学响应 3。这种增强的响应会生成比20世纪更偏北的异常东风，以响应厄尔尼诺的暖异常。这种向北扩展的异常东风模式，会导致赤道太平洋的热量再充电过程减缓 3。这意味着，在厄尔尼诺事件之后，赤道太平洋的冷水异常能够更长时间地维持，从而促使第一年的拉尼娜事件更容易持续到第二年，甚至形成“三重拉尼娜”现象 3。
- 赤道东太平洋的增温效应：除了SNP，赤道东太平洋的增温极值也进一步增强了这种向北扩展的异常模式的敏感性，为连续拉尼娜事件的发生提供了有利条件 3。
- 深层海洋热量积累：有证据表明，在过去十年（2005-2014年），南太平洋副热带海域观测到了显著的深海增温现象，其热量积累占全球海洋热量增加的四分之一。这种深海增温可能与持续的拉尼娜类状态相关联 63。这表明全球变暖可能通过影响深层海洋热量传输和积累，间接影响拉尼娜的持续性。
模型与观测的差异：
值得注意的是，当前大多数气候模型在模拟热带太平洋海表温度趋势方面存在一定的偏差。过去50年的观测数据显示，热带太平洋正在朝着一个更像拉尼娜的状态演变，即经向海表温度梯度减小和沃克环流减弱的趋势。然而，大多数气候模型预测，在温室气体导致的变暖下，赤道太平洋将演变为更像厄尔尼诺的状态 6465。这种模型与观测之间的差异可能源于模型未能准确模拟赤道太平洋对温室气体变暖的响应，甚至可能涉及到人为气溶胶对21世纪早期持续拉尼娜类条件的贡献 66。这种差异对于预测区域热带气旋活动、干旱等灾害的未来变化趋势具有重要影响 64。
综上所述，全球变暖背景下，连续拉尼娜事件频率的增加似乎是未来的一个重要趋势。副热带海温增温极值在其中扮演了关键角色，通过改变大气环流模式和海洋热量再充电过程，强化了拉尼娜的持续性。然而，气候模型在准确捕捉热带太平洋对全球变暖的响应方面仍面临挑战，这提醒我们在解读未来气候预估时需持谨慎态度，并持续改进气候模型。
6.2 预测不确定性与适应启示
尽管气候模型在预估拉尼娜事件的未来趋势方面提供了宝贵线索，但其预测仍存在显著不确定性。理解这些不确定性并提出相应的适应性策略，对于有效应对拉尼娜带来的气候风险至关重要。
气候模型对拉尼娜模拟的偏差：
当前气候模型在模拟和预测拉尼娜事件时面临多重挑战。其中一个核心问题是赤道太平洋增温趋势的争议：尽管观测数据显示热带太平洋在过去50年正朝着类似拉尼娜的状态演变（即经向海表温度梯度减小和沃克环流减弱），但大多数气候模型却预测在温室气体增暖下，赤道太平洋将演变为更像厄尔尼诺的状态 67。这种模型与观测之间的显著偏差，反映了气候模型在准确捕捉复杂海气耦合过程，特别是与ENSO相关的非线性动力学过程方面的局限性。例如，大多数模型对厄尔尼诺和拉尼娜之间不对称性的模拟仍然很差，这主要归因于对赤道太平洋温跃层沿次表层非线性动力加热（NDH）的模拟不足 67。NDH过弱以及线性动力海气耦合过弱是导致模型偏差的重要原因 67。此外，气候模型在模拟ENSO对流层水汽响应方面也存在挑战，这将影响对气候变化背景下拉尼娜对水循环影响的评估。
提升多时间尺度预测技巧的关键：
为提高拉尼娜事件的预测准确性，需要从多个方面进行改进：
- ENSO初始状态的精确利用：ENSO事件的演变高度依赖于海洋和大气系统的初始状态。例如，在ENSO的经典理论中，海洋热力结构的次表层异常是ENSO事件的先兆，其初始条件的准确指定对于ENSO的熟练预测至关重要 68。海洋盐度变异性在ENSO演变中可能发挥积极作用，特别是在西太平洋暖池区域 68。研究表明，通过包含初始海洋状态中盐度的年际变异性，可以更准确地预测拉尼娜事件，如2007/08年的拉尼娜事件 68。因此，加强对海洋次表层温度、盐度等关键物理量的观测，并将其更有效地整合到初始化方案中，是提高预测能力的关键。
- 改进海气耦合模型：模型需要更好地捕捉ENSO循环中的非线性过程和不对称性，特别是提升对赤道太平洋NDH和海气耦合强度、温跃层动力学的模拟精度 67。这包括提高模型的空间分辨率、改进次网格参数化方案，以及更准确地表示云、降水和辐射过程。
- 多尺度相互作用的理解：ENSO与其他气候变率模式（如太平洋年代际振荡PDO、大西洋多年代际振荡AMO）之间的相互作用会调制ENSO事件的强度和持续时间。深入理解这些多尺度相互作用，有助于提高ENSO的长期预测能力。
适应性政策的方向：
面对拉尼娜带来的不确定性及其潜在的全球影响，制定具有前瞻性的适应性政策至关重要：
- 气候韧性卫生系统：拉尼娜导致的极端天气（如高温、洪涝、干旱）会增加虫媒传染病（如疟疾、登革热）、水传播疾病（如腹泻、霍乱）以及心血管和呼吸道疾病的风险 4。因此，建立气候韧性的卫生系统是当务之急，包括加强疾病监测和早期预警机制 69、提升医疗基础设施应对极端事件的能力、储备必要医疗物资、培训医护人员应对气候相关健康风险等 7071。尤其要关注老年人、儿童和低收入群体等脆弱人群的健康防护 72。
- 早期预警机制：整合气象、气候、农业和公共卫生等多源数据，开发和完善多时间尺度的早期预警系统。例如，针对拉尼娜可能带来的极端降水和干旱风险，建立基于气象预测的农业干旱或洪涝预警系统，指导农户调整种植结构和水资源管理策略。对传染病，特别是蚊媒和水传播疾病，应建立基于气候预测和环境敏感度的风险预警，及时采取预防措施 7374。
- 农业和水资源管理策略：推广气候适应型农业技术，如发展耐旱/耐涝作物品种、优化灌溉方式、推广节水技术。加强水资源基础设施建设，如水库调蓄、雨水收集和非常规水资源利用，以应对干旱和洪涝双重挑战。
- 国际合作与能力建设：鉴于拉尼娜的全球性影响，加强国际间的科学研究合作，共享观测数据和预测模型，共同开发应对策略。同时，帮助发展中国家提升其气候预测能力和适应气候变化的能力。
通过不断改进科学预测能力并实施有效的适应性政策，人类社会可以更好地应对拉尼娜事件带来的挑战，最大限度地减少其对生态系统和人类福祉的负面影响。
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参考文献
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Zhimin Jian, Yue Wang, Haowen Dang, et al.
Proc Natl Acad Sci U S A. 2020 Mar 31;117(13):7044-7051. doi: 10.1073/pnas.1915510117. Epub 2020 Mar 16.
The El Niño-Southern Oscillation (ENSO), which is tightly coupled to the equatorial thermocline in the Pacific, is the dominant source of interannual climate variability, but its long-term evolution in response to climate change remains highly uncertain. This study uses Mg/Ca in planktonic foraminiferal shells to reconstruct sea surface and thermocline water temperatures (SST and TWT) for the past 142 ky in a western equatorial Pacific (WEP) core MD01-2386. Unlike the dominant 100-ky glacial-interglacial cycle recorded by SST and δO, which echoes the pattern seen in other WEP sites, the upper ocean thermal gradient shows a clear half-precessional (9.4 ky or 12.7 ky) cycle as indicated by the reconstructed and simulated temperature (ΔT) and δO differences between the surface and thermocline waters. This phenomenon is attributed to the interplay of subtropical-to-tropical thermocline anomalies forced by the antiphased meridional insolation gradients in the two hemispheres at the precessional band. In particular, the TWT shows greater variability than SST, and dominates the ΔT changes which couple with the west-east SST difference in the equatorial Pacific at the half-precessional band, implying a decisive role of the tropical thermocline in orbital-scale climate change.
8Deep-reaching thermocline mixing in the equatorial pacific cold tongue.PubMed
Chuanyu Liu, Armin Köhl, Zhiyu Liu, et al.
Nat Commun. 2016 May 12;7:11576. doi: 10.1038/ncomms11576.
Vertical mixing is an important factor in determining the temperature, sharpness and depth of the equatorial Pacific thermocline, which are critical to the development of El Ninõ and Southern Oscillation (ENSO). Yet, properties, dynamical causes and large-scale impacts of vertical mixing in the thermocline are much less understood than that nearer the surface. Here, based on Argo float and the Tropical Ocean and Atmosphere (TAO) mooring measurements, we identify a large number of thermocline mixing events occurring down to the lower half of the thermocline and the lower flank of the Equatorial Undercurrent (EUC), in particular in summer to winter. The deep-reaching mixing events occur more often and much deeper during periods with tropical instability waves (TIWs) than those without and under La Niña than under El Niño conditions. We demonstrate that the mixing events are caused by lower Richardson numbers resulting from shear of both TIWs and the EUC.
9A connection from stratospheric ozone to El Niño-Southern Oscillation.PubMed
Desmond Manatsa, Geoffrey Mukwada
Sci Rep. 2017 Jul 17;7(1):5558. doi: 10.1038/s41598-017-05111-8.
We use reanalysis and observational data to link the lower stratospheric ozone regulation of the ultraviolet radiation (UV-B) component of solar energy to ENSO modulation. Results indicate that during ENSO extremes, the Walker Circulation (WC) and Brewer Dobson Circulation are related to lower stratospheric ozone alterations east of the date line over the Pacific. These in turn are linked to upper tropospheric anomalous dipole temperature patterns on either side of the equator. The ensuing changes in geopotential height values do not only drive equatorial zonal wind anomalies in the upper troposphere that are reversed at the equatorial surface, but also impact on the intensity of the South Pacific High circulation. When the WC is enhanced, a La Nina type of circulation is indentified but if the circulation cell is inverted, the anomalous circulation results in an El Nino. Though the anomalous lower stratospheric ozone peaks during austral summer it is significant throughout the ENSO lifecycle. Hence, ENSO structure and variability are mainly linked to the lower stratospheric ozone instigated internal dynamics of the Pacific atmosphere. The ENSO forcing most likely originates from the ozone related regulation of the incoming solar UV-B radiation rather than the Pacific Ocean surface.
10The impact of ENSO on near-surface Beryllium-7.PubMed
K Schaar, T Spiegl, T Sato, et al.
J Environ Radioact. 2025 Feb;282:107592. doi: 10.1016/j.jenvrad.2024.107592. Epub 2024 Dec 9.
The concentration of near-surface Beryllium-7 contains valuable information about the atmosphere, e.g., the tropospheric circulation, precipitation pattern or specific atmospheric phenomena, like the El Niño Southern Oscillation. Here, we modelled the transport and deposition of Beryllium-7 from galactic cosmic rays for 1850-2100, using the ECHAM/MESSy atmospheric chemistry climate model, and analyzed the variability of near-surface Beryllium-7 due to the El Niño Southern Oscillation. We find that our simulated Beryllium-7 time series agree well with Beryllium-7 measurements from the international monitoring system of the Comprehensive Nuclear-Test-Ban Treaty Organization. The analysis of the time series reveals significant Beryllium-7 patterns for El Niño and La Niña in the equatorial Pacific region, controlled by precipitation anomalies and the respective state of the Walker Circulation. Furthermore, our simulations show an intensification of the Beryllium-7 pattern for El Niño and La Niña in the future. Additionally, our findings suggest that near-surface Beryllium-7 could be used as an additional indicator or even predictor of the upcoming phase of the El Niño Southern Oscillation.
11Enhanced joint impact of western hemispheric precursors increases extreme El Niño frequency under greenhouse warming.PubMed
Hyun-Su Jo, Yoo-Geun Ham
Nat Commun. 2023 Oct 11;14(1):6356. doi: 10.1038/s41467-023-42115-7.
Sea surface temperature variability over the north tropical Atlantic (NTA) and over the subtropical northeast Pacific (SNP), which is referred to as the North Pacific Meridional Mode, during the early boreal spring is known to trigger El Niño-Southern Oscillation (ENSO) events. The future changes of the influence of those northwestern hemispheric precursors on ENSO are usually examined separately, even though their joint impacts significantly differ from the individual impacts. Here, we show that the impacts of both NTA and SNP on ENSO significantly increase under greenhouse warming and that the degrees of enhancement are closely linked. The wetter mean state over the off-equatorial eastern Pacific is a single contributor that controls the impacts of both NTA and SNP on ENSO. The enhanced joint impacts of the northwestern hemispheric precursors on ENSO increase the occurrences of extreme El Niño events and the ENSO predictability under greenhouse warming.
12Response of upper tropospheric water vapor to global warming and ENSO.PubMed
Li Li, Zhiping Chen, Bingkun Wang, et al.
Sci Rep. 2024 Mar 12;14(1):5995. doi: 10.1038/s41598-024-56639-5.
The upper tropospheric water vapor is a key component of Earth's climate. Understanding variations in upper tropospheric water vapor and identifying its influencing factors is crucial for enhancing our comprehension of global climate change. While many studies have shown the impact of El Niño-Southern Oscillation (ENSO) and global warming on water vapor, how they affect the upper tropospheric water vapor remains unclear. Long-term, high-precision ERA5 specific humidity data from the European Centre for Medium-Range Weather Forecasts (ECMWF) provided the data foundation for this study. On this basis, we successfully obtained the patterns of global warming (Independent Component 1, IC1) and ENSO (Independent Component 2, IC2) by employing the strategy of independent component analysis (ICA) combined with non-parametric optimal dimension selection to investigate the upper tropospheric water vapor variations and responses to ENSO and global warming. The results indicate that global warming and ENSO are the primary factors contributing to water vapor variations in the upper troposphere, achieving the significant correlations of 0.87 and 0.61 with water vapor anomalies respectively. Together, they account for 86% of the global interannual variations in water vapor. Consistent with previous studies, our findings also find positive anomalies in upper tropospheric water vapor during El Niño years and negative anomalies during La Niña years. Moreover, the influence extent of ENSO on upper tropospheric water vapor varies with the changing seasons.
13Contrasting subtropical PV intrusion frequency and their impact on tropospheric Ozone distribution over Pacific Ocean in El-Niño and La-Niña conditions.PubMed
Debashis Nath, Wen Chen, Hans-F Graf, et al.
Sci Rep. 2017 Sep 20;7(1):11987. doi: 10.1038/s41598-017-12278-7.
Upper tropospheric equatorial westerly ducts over the Pacific Ocean are the preferred location for Rossby wave breaking events during boreal winter and spring. These subtropical wave breaking events lead to the intrusion of high PV (potential vorticity) air along the extra-tropical tropopause and transport ozone rich dry stratospheric air into the tropics. The intrusion frequency has strong interannual variability due to ENSO (El-Niño/Southern Oscillation), with more events under La-Niña and less under El-Niño conditions. This may result from stronger equatorial westerly ducts and subtropical jets during La-Niña and weaker during El-Niño. It was previously suggested that the interannual variability of the tropospheric ozone distribution over the central-eastern Pacific Ocean is mainly driven by convective activity related to ENSO and that the barotropic nature of the subtropical intrusions restricts the tracers within the UT. However, our analysis shows that tropospheric ozone concentration and subtropical intrusions account ~65% of the co- variability (below 5 km) in the outer tropical (10-25°N) central Pacific Ocean, particularly during La-Niña conditions. Additionally, we find a two-fold increase and westward shift in the intrusion frequency over the Pacific Ocean, due to the climate regime shift in SST pattern during 1997/98.
14ENSO teleconnections in the southern hemisphere: A climate network view.PubMed
Fernando Arizmendi, Marcelo Barreiro
Chaos. 2017 Sep;27(9):093109. doi: 10.1063/1.5004535.
Using functional network analysis, we study the seasonality of atmospheric connectivity and its interannual variability depending on the different phases of the El Niño-Southern Oscillation (ENSO) phenomenon. We find a strong variability of the connectivity on seasonal and interannual time scales both in the tropical and extratropical regions. In particular, there are significant changes in the southern hemisphere extratropical atmospheric connectivity during austral spring within the different stages of ENSO: We find that the connectivity patterns due to stationary Rossby waves differ during El Niño and La Niña, showing a very clear wave train originating close to Australia in the former case, as opposed to La Niña that seems to generate a wave train from the central Pacific. An attempt to understand these differences in terms of changes in the frequency of intraseasonal weather regimes cannot fully explain the differences in connectivity, even though we found the prevalence of different intraseasonal regimes in each phase of ENSO. We conclude that the differential response to extreme phases of ENSO during austral springtime is related to the forcing of waves of different tropical origins.
15Evidence for climate-driven synchrony of marine and terrestrial ecosystems in northwest Australia.PubMed
Joyce J L Ong, Adam N Rountrey, Jens Zinke, et al.
Glob Chang Biol. 2016 Aug;22(8):2776-86. doi: 10.1111/gcb.13239. Epub 2016 Mar 11.
The effects of climate change are difficult to predict for many marine species because little is known of their response to climate variations in the past. However, long-term chronologies of growth, a variable that integrates multiple physical and biological factors, are now available for several marine taxa. These allow us to search for climate-driven synchrony in growth across multiple taxa and ecosystems, identifying the key processes driving biological responses at very large spatial scales. We hypothesized that in northwest (NW) Australia, a region that is predicted to be strongly influenced by climate change, the El Niño Southern Oscillation (ENSO) phenomenon would be an important factor influencing the growth patterns of organisms in both marine and terrestrial environments. To test this idea, we analyzed existing growth chronologies of the marine fish Lutjanus argentimaculatus, the coral Porites spp. and the tree Callitris columellaris and developed a new chronology for another marine fish, Lethrinus nebulosus. Principal components analysis and linear model selection showed evidence of ENSO-driven synchrony in growth among all four taxa at interannual time scales, the first such result for the Southern Hemisphere. Rainfall, sea surface temperatures, and sea surface salinities, which are linked to the ENSO system, influenced the annual growth of fishes, trees, and corals. All four taxa had negative relationships with the Niño-4 index (a measure of ENSO status), with positive growth patterns occurring during strong La Niña years. This finding implies that future changes in the strength and frequency of ENSO events are likely to have major consequences for both marine and terrestrial taxa. Strong similarities in the growth patterns of fish and trees offer the possibility of using tree-ring chronologies, which span longer time periods than those of fish, to aid understanding of both historical and future responses of fish populations to climate variation.
16Evapotranspiration of tropical peat swamp forests.PubMed
Takashi Hirano, Kitso Kusin, Suwido Limin, et al.
Glob Chang Biol. 2015 May;21(5):1914-27. doi: 10.1111/gcb.12653. Epub 2014 Jun 27.
In Southeast Asia, peatland is widely distributed and has accumulated a massive amount of soil carbon, coexisting with peat swamp forest (PSF). The peatland, however, has been rapidly degraded by deforestation, fires, and drainage for the last two decades. Such disturbances change hydrological conditions, typically groundwater level (GWL), and accelerate oxidative peat decomposition. Evapotranspiration (ET) is a major determinant of GWL, whereas information on the ET of PSF is limited. Therefore, we measured ET using the eddy covariance technique for 4-6 years between 2002 and 2009, including El Niño and La Niña events, at three sites in Central Kalimantan, Indonesia. The sites were different in disturbance degree: a PSF with little drainage (UF), a heavily drained PSF (DF), and a drained burnt ex-PSF (DB); GWL was significantly lowered at DF, especially in the dry season. The ET showed a clear seasonal variation with a peak in the mid-dry season and a large decrease in the late dry season, mainly following seasonal variation in net radiation (Rn ). The Rn drastically decreased with dense smoke from peat fires in the late dry season. Annual ET forced to close energy balance for 4 years was 1636 ± 53, 1553 ± 117, and 1374 ± 75 mm yr(-1) (mean ± 1 standard deviation), respectively, at UF, DF, and DB. The undrained PSF (UF) had high and rather stable annual ET, independently of El Niño and La Niña events, in comparison with other tropical rainforests. The minimum monthly-mean GWL explained 80% of interannual variation in ET for the forest sites (UF and DF); the positive relationship between ET and GWL indicates that drainage by a canal decreased ET at DF through lowering GWL. In addition, ET was decreased by 16% at DB in comparison with UF chiefly because of vegetation loss through fires.
17Extreme droughts in the Amazon Basin during cyclic ENSO events coupled with Indian Ocean Dipole modes and Tropical North Atlantic warming.PubMed
Leonardo Mamani, Rita V Andreoli, Itamara Parente de Souza, et al.
Sci Total Environ. 2025 Feb 1;963:178536. doi: 10.1016/j.scitotenv.2025.178536. Epub 2025 Jan 17.
The teleconnections between El Niño-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and Tropical North Atlantic warming (+TNA) play a critical role in characterizing extreme drought events in the Amazon Basin (AB). This study examines the seven most recent drought extreme events up to 2023, using seasonal composites of the sea surface temperature and atmospheric variables over a five-quarter period starting at the austral spring(-1) of the year preceding that when the lowest water level at Manaus port was recorded. Two distinct patterns emerge, driven by consecutive ENSO events with opposite phases, referred to as cyclic La Niña-El Niño and cyclic El Niño-La Niña drought events. For these events, IOD and ENSO modes are coupled in the same phase during the springs, with ENSO triggering and enhancing IOD, and the IOD, in turn, enhancing and sustaining ENSO through Walker circulation. This interaction can amplify extratropical Rossby waves in both hemispheres, originating from the equatorial Indian and Pacific Oceans. Notably, strong positive ENSO and IOD phases trigger or sustain the +TNA by weakening northeasterlies through a Pacific-North America wave train. The IOD, ENSO and +TNA, individually or combined, influence atmospheric circulation patterns over South America through Rossby waves and anomalous Walker and Hadley circulation patterns, causing dry periods in the AB marked by negative precipitation anomalies across specific regions or the entire AB, consequently modulating the water levels at Manaus. The strong coupling of these three tropical modes is crucial to leading multiyear drought events in the AB. This study underscores the potential for a robust climate forecasting system by monitoring the oceanic indices.
18Multi-centennial phase-locking between reproduction of a South American conifer and large-scale drivers of climate.PubMed
Ignacio A Mundo, Javier Sanguinetti, Thomas Kitzberger
Nat Plants. 2021 Dec;7(12):1560-1570. doi: 10.1038/s41477-021-01038-1. Epub 2021 Dec 14.
Climate forcings determine the episodic occurrence of local climate anomalies that trigger the occurrence of masting events (massive, synchronized and intermittent seed production by perennial plants). This suggests some kind of phase-locking of the reproductive cycles of individual plants to the climatological cycle, thus further reinforcing reproductive synchrony and the Moran effect. We propose a dendrochronological approach to filter out the long-term direct effects of climate on tree radial growth and temporal reproductive effort by sex by using actual trees as climatic controls to reconstruct masting events in Araucaria araucana, a long-lived dioecious masting conifer. In this way, we developed a multi-century-long tree masting reconstruction for South America using female-male radial growth determined by differences in timing and magnitude of the reproductive effort between sexes. We provide evidence for a regional synchronizing mechanism of masting which is drought induced by strong cold La Niña phases of El Niño/Southern Oscillation (ENSO) amplified by the positive phases of the Southern Annular Mode (SAM) that activate both female and male cone bud formation during year -2 before seed fall; that is, a long-term phase-locking between the ENSO cycle and the reproductive cycle modulated by the strength of SAM. In addition, our regional index of masting frequency showed its maximum during the late twentieth century relative to the previous centuries, suggesting that the species is currently at its maximum masting frequency concurrent with a period of enhanced temperature and drought conditions in Patagonia, probably driven by the positive phase of the SAM.
19Analyzing climate variations at multiple timescales can guide Zika virus response measures.PubMed
Ángel G Muñoz, Madeleine C Thomson, Lisa Goddard, et al.
Gigascience. 2016 Oct 6;5(1):1-6. doi: 10.1186/s13742-016-0146-1.
BACKGROUND: The emergence of Zika virus (ZIKV) in Latin America and the Caribbean in 2014-2016 occurred during a period of severe drought and unusually high temperatures, conditions that have been associated with the 2015-2016 El Niño event, and/or climate change; however, no quantitative assessment has been made to date. Analysis of related flaviviruses transmitted by the same vectors suggests that ZIKV dynamics are sensitive to climate seasonality and longer-term variability and trends. A better understanding of the climate conditions conducive to the 2014-2016 epidemic may permit the development of climate-informed short and long-term strategies for ZIKV prevention and control. RESULTS: Using a novel timescale-decomposition methodology, we demonstrate that the extreme climate anomalies observed in most parts of South America during the current epidemic are not caused exclusively by El Niño or climate change, but by a combination of climate signals acting at multiple timescales. In Brazil, the dry conditions present in 2013-2015 are primarily explained by year-to-year variability superimposed on decadal variability, but with little contribution of long-term trends. In contrast, the warm temperatures of 2014-2015 resulted from the compound effect of climate change, decadal and year-to-year climate variability. CONCLUSIONS: ZIKV response strategies made in Brazil during the drought concurrent with the 2015-2016 El Niño event, may require revision in light of the likely return of rainfall associated with the borderline La Niña event expected in 2016-2017. Temperatures are likely to remain warm given the importance of long term and decadal scale climate signals.
20Recent global-warming hiatus tied to equatorial Pacific surface cooling.PubMed
Yu Kosaka, Shang-Ping Xie
Nature. 2013 Sep 19;501(7467):403-7. doi: 10.1038/nature12534. Epub 2013 Aug 28.
Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970-2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.
21Greenhouse warming and the 21st century hydroclimate of southwestern North America.PubMed
Richard Seager, Gabriel A Vecchi
Proc Natl Acad Sci U S A. 2010 Dec 14;107(50):21277-82. doi: 10.1073/pnas.0910856107. Epub 2010 Dec 13.
Climate models robustly predict that the climate of southwestern North America, defined as the area from the western Great Plains to the Pacific Ocean and from the Oregon border to southern Mexico, will dry throughout the current century as a consequence of rising greenhouse gases. This regional drying is part of a general drying of the subtropics and poleward expansion of the subtropical dry zones. Through an analysis of 15 coupled climate models it is shown here that the drying is driven by a reduction of winter season precipitation associated with increased moisture divergence by the mean flow and reduced moisture convergence by transient eddies. Due to the presence of large amplitude decadal variations of presumed natural origin, observations to date cannot confirm that this transition to a drier climate is already underway, but it is anticipated that the anthropogenic drying will reach the amplitude of natural decadal variability by midcentury. In addition to this drop in total precipitation, warming is already causing a decline in mountain snow mass and an advance in the timing of spring snow melt disrupting the natural water storage systems that are part of the region's water supply system. Uncertainties in how radiative forcing will impact the tropical Pacific climate system create uncertainties in the amplitude of drying in southwest North America with a La Niña-like response creating a worst case scenario of greater drying.
22Impact of El Niño-Southern oscillation on human leptospirosis in Colombia at different spatial scales.PubMed
Clara Arias-Monsalve, Alejandro Builes-Jaramillo
J Infect Dev Ctries. 2019 Dec 31;13(12):1108-1116. doi: 10.3855/jidc.11702.
INTRODUCTION: Leptospirosis is a zoonotic disease caused by a bacteria of the genus Leptospira. Climate is key in order to understand leptospirosis dynamics. El Niño Southern Oscillation is the main modulator of climate in Colombia. Our goal was to analyze the changes that occurred in number of cases and incidence rate of leptospirosis during La Niña and El Niño episodes in Colombia at three spatial scales in the period between 2007 and 2015. METHODOLOGY: A cross-sectional retrospective study was performed. DATA ANALYSIS: correlation and lagged cross correlation between time series of Oscillation Niño Index and time series of standardized number of leptospirosis cases; construction of annual cycle of leptospirosis; comparison of changes of number of cases between Neutral, periods with El Niño and Neutral periods with La Niña. RESULTS: At the national level, monthly number of cases raised a 25% during La Niña and decreased of 17% during El Niño. At departmental level, increase of cases in both phases of ENSO, depending on the location in the country, was found. At the municipal level, 17 have a rise in the number of cases during La Niña months. Of those, seven presented also an increase of cases during El Niño months and eight have a significant negative correlation with ONI. CONCLUSIONS: In Colombia, there exists a relationship between leptospirosis and the excess and lack of rainfall related with ENSO. The contrasting results from each spatial scale, reinforce that leptospirosis is a multidimensional disease with high complex interactions among its determinants.
23Variability of Suitable Habitat of Western Winter-Spring Cohort for Neon Flying Squid in the Northwest Pacific under Anomalous Environments.PubMed
Wei Yu, Xinjun Chen, Qian Yi, et al.
PLoS One. 2015 Apr 29;10(4):e0122997. doi: 10.1371/journal.pone.0122997. eCollection 2015.
We developed a habitat suitability index (HSI) model to evaluate the variability of suitable habitat for neon flying squid (Ommastrephes bartramii) under anomalous environments in the Northwest Pacific Ocean. Commercial fisheries data from the Chinese squid-jigging vessels on the traditional fishing ground bounded by 35°-45°N and 150°-175°E from July to November during 1998-2009 were used for analyses, as well as the environmental variables including sea surface temperature (SST), chlorophyll-a (Chl-a) concentration, sea surface height anomaly (SSHA) and sea surface salinity (SSS). Two empirical HSI models (arithmetic mean model, AMM; geometric mean model, GMM) were established according to the frequency distribution of fishing efforts. The AMM model was found to perform better than the GMM model. The AMM-based HSI model was further validated by the fishery and environmental data in 2010. The predicted HSI values in 1998 (high catch), 2008 (average catch) and 2009 (low catch) indicated that the squid habitat quality was strongly associated with the ENSO-induced variability in the oceanic conditions on the fishing ground. The La Niña events in 1998 tended to yield warm SST and favorable range of Chl-a concentration and SSHA, resulting in high-quality habitats for O. bartramii. While the fishing ground in the El Niño year of 2009 experienced anomalous cool waters and unfavorable range of Chl-a concentration and SSHA, leading to relatively low-quality squid habitats. Our findings suggest that the La Niña event in 1998 tended to result in more favorable habitats for O. bartramii in the Northwest Pacific with the gravity centers of fishing efforts falling within the defined suitable habitat and yielding high squid catch; whereas the El Niño event in 2009 yielded less favorable habitat areas with the fishing effort distribution mismatching the suitable habitat and a dramatic decline of the catch of O. bartramii. This study might provide some potentially valuable insights into exploring the relationship between the underlying squid habitat and the inter-annual environmental change.
24El Niño southern oscillation, weather patterns, and bacillary dysentery in the Yangtze River Basin, China.PubMed
Caiji Li, Xiaowen Wang, Zehua Liu, et al.
Glob Health Res Policy. 2024 Nov 11;9(1):45. doi: 10.1186/s41256-024-00389-4.
BACKGROUND: Increasingly intense weather anomalies associated with interannual climate variability patterns, like El Niño-southern oscillation (ENSO), could exacerbate the occurrence and transmission of infectious diseases. However, research in China remains limited in understanding the impacts and intermediate weather changes of ENSO on bacillary dysentery (BD). This study aimed to reveal the relationship between ENSO, weather conditions, and the incidence of BD, and to identify the potential meteorological pathways moderated by ENSO in the ENSO-BD connections. METHODS: BD disease data and meteorological data, as well as ENSO index, from 2005 to 2020 were obtained for 95 cities in the Yangtze River Basin. We first established the associations between ENSO events and BD, ENSO and weather, as well as weather and BDs using two-stage statistical models. Then, we applied a causal mediation analysis to identify the specific meteorological changes in the ENSO-BD relationship. RESULTS: In the Yangtze River Basin, both El Niño (IRR: 1.06, 95%CI: 1.04 ~ 1.08) and La Niña (IRR: 1.03, 95%CI: 1.02 ~ 1.05) events were found to increase the risk of BD. Variations of ENSO index were associated with changes in local weather conditions. Both the increases in regional temperatures and rainfall were associated with a higher risk of BD. In the casual mediation analyses, we identified that higher temperatures and excessive rainfall associated with La Niña and El Niño events mediated the ENSO's effect on BD, with mediation proportions of 38.58% and 34.97%, respectively. CONCLUSIONS: Long-term climate variability, like ENSO, can affect regional weather conditions and lead to an increased risk of BD. We identified the mediating weather patterns in the relationship between ENSO and BD, which could improve targeted health interventions and establish an advanced early warning system in response to the BD epidemic.
25Spatiotemporal Variation in Rainfall Erosivity and Correlation with the ENSO on the Tibetan Plateau since 1971.PubMed
Bohao Cui, Yili Zhang, Linshan Liu, et al.
Int J Environ Res Public Health. 2021 Oct 21;18(21):11054. doi: 10.3390/ijerph182111054.
Soil erosion is a serious ecological problem in the fragile ecological environment of the Tibetan Plateau (TP). Rainfall erosivity is one of the most important factors controlling soil erosion and is associated with the El Niño southern oscillation (ENSO). However, there is a lack of studies related to the spatial distribution and temporal trends of rainfall erosivity on the TP as a whole. Additionally, the understanding of the general influence of ENSO on rainfall erosivity across the TP remains to be developed. In this study, long-term (1971-2020) daily precipitation data from 91 meteorological stations were selected to calculate rainfall erosivity. The analysis combines co-kriging interpolation, Sen's slope estimator, and the Mann-Kendall trend test to investigate the spatiotemporal patten of rainfall erosivity across the TP. The Oceanic Niño Index (ONI) and multivariate ENSO Index (MEI) were chosen as ENSO phenomenon characterization indices, and the relationship between ENSO and rainfall erosivity was explored by employing a continuous wavelet transform. The results showed that an increasing trend in annual rainfall erosivity was detected on the TP from 1971 to 2020. The seasonal and monthly rainfall erosivity was highly uneven, with the summer erosivity accounting for 60.36%. The heterogeneous spatial distribution of rainfall erosivity was observed with an increasing trend from southeast to northwest. At the regional level, rainfall erosivity in the southeastern TP was mainly featured by a slow increase, while in the northwest was more destabilizing and mostly showed no significant trend. The rainfall erosivity on the whole TP was relatively high during non-ENSO periods and relatively low during El Niño/La Niña periods. It is worth noting that rainfall erosivity in the northwest TP appears to be more serious during the La Niña event. Furthermore, there were obvious resonance cycles between the rainfall erosivity and ENSO in different regions of the plateau, but the cycles had pronounced discrepancies in the occurrence time, direction of action and intensity. These findings contribute to providing references for soil erosion control on the TP and the formulation of future soil conservation strategies.
26Factors affecting marine debris deposition at French Frigate Shoals, Northwestern Hawaiian Islands Marine National Monument, 1990-2006.PubMed
Carey Morishige, Mary J Donohue, Elizabeth Flint, et al.
Mar Pollut Bull. 2007 Aug;54(8):1162-9. doi: 10.1016/j.marpolbul.2007.04.014. Epub 2007 Jun 18.
Data on the amount and type of small debris items deposited on the beaches of the Hawaiian Islands National Wildlife Refuge Tern Island station, French Frigate Shoals were collected over 16 years. We calculated deposition rates and investigated the relationship among deposition and year, season, El Niño and La Niña events from 1990 to 2006. In total 52,442 debris items were collected with plastic comprising 71% of all items collected. Annual debris deposition varied significantly (range 1116-5195 items) but was not influenced by season. Debris deposition was significantly greater during El Niño events as compared to La Niña events. Although often deduced to influence floating marine pollution, this study provides the first quantitative evidence of the influence of El Niño/La Niña cycles on marine debris deposition.
27Optimized spatial and temporal pattern for coral bleaching heat stress alerts for China's coral reefs.PubMed
Xiuling Zuo, Binni Qin, Juncan Teng, et al.
Mar Environ Res. 2023 Oct;191:106152. doi: 10.1016/j.marenvres.2023.106152. Epub 2023 Aug 19.
Most studies on coral bleaching alerts use common Degree Heating Week (DHW) thresholds; however, these may underestimate historical patterns of heat stress for coral reef ecosystems. Taking an optimized DHW threshold for coral bleaching alerts for Coral Reef Watch (CRW) and Coral Reef Temperature Anomaly Database (CoRTAD) products, we analyzed the precise spatial and temporal pattern of heat stress on China's coral reefs from 2010 to 2021 in the South China Sea (SCS) and the Beibu Gulf (BG). We compared acute heat stress using common and optimized thresholds. Results indicated that the ocean warming rate in 2010-2021 was approximately 0.43 ± 0.22 °C/10a, showing a significant increase in the northern SCS and the BG. More severe bleaching events were predicted by the optimized thresholds and the high-frequency areas were mainly in the northern SCS. The number and intensity of years with severe heat stress anomalies was in the order 2020 > 2014 > 2010 > 2015. Heat stress duration was the longest in the Xisha Islands among offshore archipelagos, and longest in 2020-2021 in Weizhou Island in BG in the relative high-latitude inshore reefs. These abnormal events were mainly caused by El Niño, but La Niña was also involved in 2020.
28State of corals and coral reefs of the Galápagos Islands (Ecuador): Past, present and future.PubMed
Peter W Glynn, Joshua S Feingold, Andrew Baker, et al.
Mar Pollut Bull. 2018 Aug;133:717-733. doi: 10.1016/j.marpolbul.2018.06.002. Epub 2018 Jun 22.
Coral populations and structural coral reefs have undergone severe reductions and losses respectively over large parts of the Galápagos Islands during and following the 1982-83 El Niño event. Coral tissue loss amounted to 95% across the Archipelago. Also at that time, all coral reefs in the central and southern islands disappeared following severe degradation and eventual collapse due primarily to intense bioerosion and low recruitment. Six sites in the southern islands have demonstrated low to moderate coral community (scattered colonies, but no carbonate framework) recovery. The iconic pocilloporid reef at Devil's Crown (Floreana Island) experienced recovery to 2007, then severe mortality during a La Niña cooling event, and is again (as of 2017) undergoing rapid recovery. Notable recovery has occurred at the central (Marchena) and northern islands (Darwin and Wolf). Of the 17 structural reefs first observed in the mid-1970s, the single surviving reef (Wellington Reef) at Darwin Island remains in a positive growth mode. The remainder either degraded to a coral community or was lost. Retrospective analyses of the age structure of corals killed in 1983, and isotopic signatures of the skeletal growth record of massive corals suggest the occurrence of robust coral populations during at least a 500-year period before 1983. The greatest potential threats to the recovery and persistence of coral reefs include: ocean warming and acidification, bioerosion, coral diseases, human population growth (increasing numbers of residents and tourists), overfishing, invasive species, pollution, and habitat destruction. Such a diverse spectrum of disturbances, acting alone or in combination, are expected to continue to cause local and archipelago-wide mortality and degradation of the coral reef ecosystem.
29Predicting coral-reef futures from El Niño and Pacific Decadal Oscillation events.PubMed
Peter Houk, Anthony Yalon, Selino Maxin, et al.
Sci Rep. 2020 May 8;10(1):7735. doi: 10.1038/s41598-020-64411-8.
El Niño Southern Oscillation (ENSO) events modulate oceanographic processes that control temperature and productivity in tropical waters, yet potential interactions with low frequency climate variability, such as the Pacific Decadal Oscillation (PDO), are poorly understood. We show that ENSO and PDO together predicted (i) maximum sea-surface temperatures (SST), which were associated with coral bleaching and declines in coral cover, and (ii) maximum chlorophyll-a concentrations, which were associated with high densities of coral-predatory Acanthaster starfish, across the tropical north Pacific Ocean since 1980. Asynchrony between the positive PDO and negative ENSO (i.e., La Niña) was associated with peaks in annual SST. By contrast, synchrony between the positive PDO and positive ENSO (i.e., El Niño) was associated with peaks in chlorophyll-a. Both conditions led to ecological disturbances and significant loss of coral cover, however, spatial models revealed where impacts to reefs were expected under varying climate scenarios. The 2015/17 ENSO event was coupled with a positive PDO and resulted in high SST and Acanthaster abundances in eastern Micronesia, while positive coral growth occurred in western Micronesia. Our novel approach for forecasting coral growth into the future may be applicable to other oceanic regions with differing oceanographic modulators.
30Impacts of Strong ENSO Events on Fish Communities in an Overexploited Ecosystem in the South China Sea.PubMed
Miao Li, Youwei Xu, Mingshuai Sun, et al.
Biology (Basel). 2023 Jul 1;12(7):946. doi: 10.3390/biology12070946.
To better understand how fish communities respond to environmental changes under extreme climate events, we examine changes in fish communities in Beibu Gulf during strong El Niño and La Niña events. Strong La Niña and El Niño events affect the composition, abundance, and distribution of fish communities in Beibu Gulf. Fish community distribution and composition change before and after La Niña and El Niño events, and dominant species within them change with stable fishing intensity. The abundance and distribution of small pelagic fish such as Japanese jack mackerel () and Japanese scad () are the most affected. Using a generalized additive model (GAM), we explore relationships between the abundance of and and a suite of environmental variables. The GAM results revealed that sea surface salinity and sea surface temperature best explain changes in catch per unit effort of these two species during a La Niña event; depth, sea surface temperature, and mixed layer depth during an El Niño event. The results obtained in this study will offer support for implementing more-accurate, scientific fisheries management measures.
31Effects of climate-change-driven gradual and acute temperature changes on shark and ray species.PubMed
Geoffrey J Osgood, Easton R White, Julia K Baum
J Anim Ecol. 2021 Nov;90(11):2547-2559. doi: 10.1111/1365-2656.13560. Epub 2021 Jul 6.
Climate change is altering distributions and abundances of marine species through both gradual and acute changes in temperature and productivity. Due to their high mobility and metabolic rates, elasmobranchs (sharks and rays) are likely to redistribute across latitudes and depths as they thermoregulate, but little is known about their responses to these climatic changes, which could vary widely across this diverse group of species. Here, we assessed how species with differing mobility and ecology responded to gradual changes in daily sea surface temperature (SST) and acute temperature anomalies, caused by the El Niño-Southern Oscillation (ENSO), at Cocos Island, Costa Rica, the site of multiple marine heatwaves. We used generalized linear mixed models to analyse 34,342 records of relative abundance or frequency of occurrence for seven shark and ray species collected in 27 years (1993-2019) by a dive company. We compared effect sizes for SST and the Oceanic Niño Index across the different species, which vary widely in body size and mobility. Large, mobile species responded strongly but inconsistently to temperature. For scalloped hammerhead sharks Sphyrna lewini, a 1℃ rise in SST reduced counts by over 14%, and dropped the occurrence of their large schools by almost one-fifth (19.4%). Mobula ray occurrence also declined substantially with a few degrees rise in SST, whereas tiger shark Galeocerdo cuvier occurrence sharply increased. These species also had divergent responses to the ENSO: S. lewini and G. cuvier were sighted with greater frequency during La Niña events, and their abundance dropped considerably during El Niño events-over a twofold decline between a strong La Niña and strong El Niño for S. lewini. In contrast, Mobula rays showed little response to ENSO. The smaller and sedentary Triaenodon obesus exhibited the weakest response of all species to both SST and the ENSO, reflecting its lower metabolic rates and mobility. Climate change will continue to impact elasmobranchs, even for smaller and more localized species, with the potential to impact the effectiveness of marine protected areas (MPAs). Our results compel further work on the diversity of elasmobranch responses to environmental change.
32Can juvenile supply predict future abundance of large-bodied reef fishes?PubMed
Shaun K Wilson, Martial Depczynski, Christopher J Fulton, et al.
Mar Environ Res. 2024 Jul;199:106607. doi: 10.1016/j.marenvres.2024.106607. Epub 2024 Jun 13.
The extent to which juvenile abundance can predict future populations of lethrinids at Ningaloo Reef was assessed using size frequency data collected over 13 consecutive years. Annual abundance of juvenile lethrinids (<5 cm TL) was highest in northern Ningaloo during La Niña years, when seawater is warmer and oceanic currents stronger. Juvenile lethrinid abundance explained 35% of the variance in 1-2 year-old Lethrinus nebulosus abundance the following year, a steeper relationship in the north suggesting greater survival of juveniles. Juvenile lethrinid abundance was also positively correlated to abundance of 1-2 year-old L. atkinsoni in the southern region of Ningaloo. Abundance of juvenile lethrinids were however poor predictors of L. nebulosus and L. atkinsoni older than 2 years of age. Post settlement processes likely weaken the link between juvenile supply and abundance of lethrinids >2 years old making it difficult to accurately quantify the overall size of future lethrinid populations.
33Interannual variability of distribution, abundance and population dynamics of the smooth hammerhead Sphyrna zygaena (Linnaeus, 1758) in the central-southeast Pacific Ocean.PubMed
Juana López-Martínez, Carmen Cabanilla-Carpio, Walter Ruiz Choez, et al.
J Fish Biol. 2020 Aug;97(2):341-353. doi: 10.1111/jfb.14360. Epub 2020 Jun 8.
This study provides information on the population dynamics of the smooth hammerhead shark Sphyrna zygaena in the central-southeast Pacific Ocean. The samples were obtained from artisanal fisheries from 2008 to 2013 to analyse cohorts, growth, mortality, abundance and recruitment using methods based on length and relative age and an inference multi-model. According to the von Bertalanffy growth model, the results indicated that the species showed from three to seven cohorts annually and slow growth (W = 57.20%): L = 292.86 cm, K = 0.141 per year and t = -2.26. Length of sexual maturity was 239.30 and 209.10 cm at first capture; the average natural mortality value was 0.231 per year, by fishing 0.051 per year with a total mortality of 0.26 1 per year and exploitation rate of 0.15. Interannual variability was recorded in biomass with an average of 7367.24 tonnes, as well as a spatial permanence pattern. The results suggest that the La Niña event biologically favours the population in the area. The information from this study is essential for better understanding the species population and serves as a basis for future actions of management and conservation of S. zygaena.
34Dynamic habitat suitability modelling reveals rapid poleward distribution shift in a mobile apex predator.PubMed
Nicholas J Hill, Andrew J Tobin, April E Reside, et al.
Glob Chang Biol. 2016 Mar;22(3):1086-96. doi: 10.1111/gcb.13129. Epub 2015 Dec 15.
Many taxa are undergoing distribution shifts in response to anthropogenic climate change. However, detecting a climate signal in mobile species is difficult due to their wide-ranging, patchy distributions, often driven by natural climate variability. For example, difficulties associated with assessing pelagic fish distributions have rendered fisheries management ill-equipped to adapt to the challenges posed by climate change, leaving pelagic species and ecosystems vulnerable. Here, we demonstrate the value of citizen science data for modelling the dynamic habitat suitability of a mobile pelagic predator (black marlin, Istiompax indica) within the south-west Pacific Ocean. The extensive spatial and temporal coverage of our occurrence data set (n = 18 717), collected at high resolution (~1.85 km(2) ), enabled identification of suitable habitat at monthly time steps over a 16-year period (1998-2013). We identified considerable monthly, seasonal and interannual variability in the extent and distribution of suitable habitat, predominately driven by chlorophyll a and sea surface height. Interannual variability correlated with El Nino Southern Oscillation (ENSO) events, with suitable habitat extending up to ~300 km further south during La Nina events. Despite the strong influence of ENSO, our model revealed a rapid poleward shift in the geometric mean of black marlin habitat, occurring at 88.2 km decade(-1) . By incorporating multiple environmental factors at monthly time steps, we were able to demonstrate a rapid distribution shift in a mobile pelagic species. Our findings suggest that the rapid velocity of climate change in the south-west Pacific Ocean is likely affecting mobile pelagic species, indicating that they may be more vulnerable to climate change than previously thought.
35ENSO-induced co-variability of Salinity, Plankton Biomass and Coastal Currents in the Northern Gulf of Mexico.PubMed
Fabian A Gomez, Sang-Ki Lee, Frank J Hernandez, et al.
Sci Rep. 2019 Jan 17;9(1):178. doi: 10.1038/s41598-018-36655-y.
The northern Gulf of Mexico (GoM) is a region strongly influenced by river discharges of freshwater and nutrients, which promote a highly productive coastal ecosystem that host commercially valuable marine species. A variety of climate and weather processes could potentially influence the river discharges into the northern GoM. However, their impacts on the coastal ecosystem remain poorly described. By using a regional ocean-biogeochemical model, complemented with satellite and in situ observations, here we show that El Niño - Southern Oscillation (ENSO) is a main driver of the interannual variability in salinity and plankton biomass during winter and spring. Composite analysis of salinity and plankton biomass anomalies shows a strong asymmetry between El Niño and La Niña impacts, with much larger amplitude and broader areas affected during El Niño conditions. Further analysis of the model simulation reveals significant coastal circulation anomalies driven by changes in salinity and winds. The coastal circulation anomalies in turn largely determine the spatial extent and distribution of the ENSO-induced plankton biomass variability. These findings highlight that ENSO-induced changes in salinity, plankton biomass, and coastal circulation across the northern GoM are closely interlinked and may significantly impact the abundance and distribution of fish and invertebrates.
36Drivers of Marine Phytoplankton Diversity and Connectivity in the Galápagos Archipelago Spanning an ENSO Cycle.PubMed
Prisca Lim, Harvey Seim, Oliva Torano, et al.
Environ Microbiol. 2025 Jul;27(7):e70146. doi: 10.1111/1462-2920.70146.
The Galápagos Islands are a biodiversity hotspot, largely due to the Equatorial Undercurrent (EUC) which supplies nutrient-rich waters to the euphotic zone and supports enhanced levels of primary productivity performed by phytoplankton. Understanding phytoplankton responses to changing environmental conditions is crucial for regional conservation and management efforts. Research cruises conducted between 2014 and 2022, spanning a major El Niño event in 2015 and a La Niña event in 2022, observed varying oceanic conditions and diverse phytoplankton community composition. At most EUC-influenced stations, larger-sized phytoplankton groups (≥ 5 μm) were dominant while warmer, oligotrophic sites favoured smaller-sized phytoplankton groups (< 5 μm). Predictably, nutrient supply was suppressed during the El Niño event associated with the weakening of the EUC and deepening of the thermocline. Counterintuitively, nutrient levels were not significantly enhanced during the La Niña event likely because increased stratification between the mixed and deep water layers reduced entrainment, particularly at Eastern stations. Protist community composition was evaluated using 18S rRNA gene metabarcoding; the majority of detected OTUs were associated with upwelling conditions prevalent around the archipelago. Taxonomic variability reflected heterogeneous environmental conditions generated by the convergence of multiple ocean currents. These results highlight the dynamic interplay of physical and biological factors shaping primary productivity in the Galápagos marine ecosystem.
37Morphofunctional changes of phytoplankton community during pluvial anomaly in a tropical reservoir.PubMed
F R A Câmara, O Rocha, E K R Pessoa, et al.
Braz J Biol. 2015 Aug;75(3):628-37. doi: 10.1590/1519-6984.19513. Epub 2015 Aug 25.
The present study focuses on the structure and function of phytoplankton community during periods of marked changes in hydrological traits, influenced by an atypical climatic event (La Niña) and its impact on Armando Ribeiro Gonçalves Reservoir of Rio Grande do Norte, situated in the Caatinga biome of northeastern Brazil. The main questions addressed were: What are the effects of environmental factors on the temporal variation of Morphologically Based Functional Group (MBFG) of phytoplankton community? How does the composition of cyanobacterial species shift in relation to high and low trends of phytoplankton diversity? The samples were collected monthly during 2008-2009 and analyzed for pH, temperature, electrical conductivity, dissolved oxygen content and the nutrients, such as, nitrate-nitrogen, ammoniacal nitrogen, total nitrogen and orthophosphate. Phytoplankton samples were collected for both qualitative and quantitative analyses to evaluate species richness index and species diversity index. The data was divided into two distinct hydrodynamic periods of instability and stability. The results demonstrate considerable changes in dissolved oxygen content, water transparency and nitrogen nutrients, which directly influenced the MBFG of phytoplankton community in space and time. The instability of reservoir water was caused by heavy rainfall, which exerts atypical external disturbances. The seasonal variation of MBFG demonstrates a change in cyanobacterial composition and their diversity during instability and stability periods. MBFG VII, composed by colonial cyanobacteria with mucilage, was associated with reduced values of electrical conductance and alterations in pH. The predominance of filamentous species with heterocyst (MBFG III) occurs only during the hydrodynamic stability period and did not show significant association with analyzed parameters. The co-dominance of MBGFs III, V and VII along with high species diversity of phytoplankton community occurred during the second hydrodynamic instability period which was associated with the reduction in water temperature. It is concluded that the decrease in cyanobacterial species dominance and the general increase in the diversity of phytoplankton community are influenced by pluvial anomaly. The higher water level during the period of pluvial anomaly resulted in nutrient pulse and the mixing of water column in the reservoir, which determined the MBPG phytoplankton community distribution.
38Glacial melt disturbance shifts community metabolism of an Antarctic seafloor ecosystem from net autotrophy to heterotrophy.PubMed
Ulrike Braeckman, Francesca Pasotti, Ralf Hoffmann, et al.
Commun Biol. 2021 Jan 29;4(1):148. doi: 10.1038/s42003-021-01673-6.
Climate change-induced glacial melt affects benthic ecosystems along the West Antarctic Peninsula, but current understanding of the effects on benthic primary production and respiration is limited. Here we demonstrate with a series of in situ community metabolism measurements that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. With little glacial melt disturbance (during cold El Niño spring 2015), clear waters enabled high benthic microalgal production, resulting in net autotrophic benthic communities. In contrast, water column turbidity caused by increased glacial melt run-off (summer 2015 and warm La Niña spring 2016) limited benthic microalgal production and turned the benthic communities net heterotrophic. Ongoing accelerations in glacial melt and run-off may steer shallow Antarctic seafloor ecosystems towards net heterotrophy, altering the metabolic balance of benthic communities and potentially impacting the carbon balance and food webs at the Antarctic seafloor.
39Effect of seawater temperature, pH, and nutrients on the distribution and character of low abundance shallow water benthic foraminifera in the Galápagos.PubMed
Alexander F Humphreys, Jochen Halfar, James C Ingle, et al.
PLoS One. 2018 Sep 12;13(9):e0202746. doi: 10.1371/journal.pone.0202746. eCollection 2018.
In order to help predict the effects of anthropogenic stressors on shallow water carbonate environments, it is important to focus research on regions containing natural oceanographic gradients, particularly with respect to interactions between oceanography and ecologically sensitive carbonate producers. The Galápagos Archipelago, an island chain in the eastern equatorial Pacific, spans a natural nutrient, pH, and temperature gradient due to the interaction of several major ocean currents. Further, the region is heavily impacted by the El Niño-Southern Oscillation (ENSO) and the Galápagos exhibited widespread coral bleaching and degradation following the strong ENSO events of 1982-1983 and 1997-1998. These findings are coupled with reports of unusually low abundances of time-averaged benthic foraminiferal assemblages throughout the region. Foraminifera, shelled single-celled protists, are sensitive to environmental change and rapidly respond to alterations to their surrounding environment, making them ideal indicator species for the study of reef water quality and health. Here, statistical models and analyses were used to compare modern shallow water benthic foraminiferal assemblages from 19 samples spanning the Galápagos Archipelago to predominant oceanographic parameters at each collection site. Fisher α diversity indices, Ternary diagrams, Canonical Correspondence Analysis, regression tree analysis and FORAM-Index (FI; a single metric index for evaluating water quality associated with reef development) implied a combined impact from ENSO and upwelling from Equatorial Undercurrent (EUC) waters to primarily impact foraminiferal abundances and drive assemblage patterns throughout the archipelago. For instance, repeated ENSO temperature anomalies might be responsible for low foraminiferal density, while chronically high nutrients and low aragonite saturation and low pH-induced by EUC upwelling and La Niña anomalies-likely inhibited post-ENSO recovery, and caused foraminiferal assemblages to exhibit a heterotrophic dominance in the southern archipelago. What resulted are low FI values in the southern collection sites, indicating environments not conducive to endosymbiont development and/or recovery.
40El Niño Southern Oscillation influences the abundance and movements of a marine top predator in coastal waters.PubMed
Kate R Sprogis, Fredrik Christiansen, Moritz Wandres, et al.
Glob Chang Biol. 2018 Mar;24(3):1085-1096. doi: 10.1111/gcb.13892. Epub 2017 Oct 8.
Large-scale climate modes such as El Niño Southern Oscillation (ENSO) influence population dynamics in many species, including marine top predators. However, few quantitative studies have investigated the influence of large-scale variability on resident marine top predator populations. We examined the effect of climate variability on the abundance and temporary emigration of a resident bottlenose dolphin (Tursiops aduncus) population off Bunbury, Western Australia (WA). This population has been studied intensively over six consecutive years (2007-2013), yielding a robust dataset that captures seasonal variations in both abundance and movement patterns. In WA, ENSO affects the strength of the Leeuwin Current (LC), the dominant oceanographic feature in the region. The strength and variability of the LC affects marine ecosystems and distribution of top predator prey. We investigated the relationship between dolphin abundance and ENSO, Southern Annular Mode, austral season, rainfall, sea surface salinity and sea surface temperature (SST). Linear models indicated that dolphin abundance was significantly affected by ENSO, and that the magnitude of the effect was dependent upon season. Dolphin abundance was lowest during winter 2009, when dolphins had high temporary emigration rates out of the study area. This coincided with the single El Niño event that occurred throughout the study period. Coupled with this event, there was a negative anomaly in SST and an above average rainfall. These conditions may have affected the distribution of dolphin prey, resulting in the temporary emigration of dolphins out of the study area in search of adequate prey. This study demonstrated the local effects of large-scale climatic variations on the short-term response of a resident, coastal delphinid species. With a projected global increase in frequency and intensity of extreme climatic events, resident marine top predators may not only have to contend with increasing coastal anthropogenic activities, but also have to adapt to large-scale climatic changes.
41Impact of monsoon teleconnections on regional rainfall and vegetation dynamics in Haryana, India.PubMed
Abhilash Singh Chauhan, Surender Singh, Rajesh Kumar Singh Maurya, et al.
Environ Monit Assess. 2022 Jun 7;194(7):485. doi: 10.1007/s10661-022-10146-0.
Our study has investigated the impact of El Niño-Southern Oscillation (ENSO) on spatio-temporal dynamics of Indian summer monsoon rainfall (ISMR) as well as vegetation for a period of 1980 to 2019 at regional scale in Haryana, India. The gridded rainfall datasets of India Meteorological Department (IMD) were examined on monthly and seasonal scale using various statistical methods like mean climatology, coefficient of variation, slope of linear, Sen's slope, Mann-Kendall Z statistic, and hierarchical cluster analysis. The influence of ENSO on spatial distribution of ISMR was observed, where we found increasing and decreasing rainfall patterns during La Niña and El Niño years, respectively. We attempted to establish a link between ISMR and various teleconnections using time series of the National Oceanic and Atmospheric Administration (NOAA) Physical Sciences Laboratory, and statistically significant and positive correlation was observed with the Southern Oscillation Index (SOI), whereas significantly negative correlations were observed with SST of Niño 3, Niño 3.4, and Niño 4 regions. The gridded datasets of the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis V5 (ERA5) were used to evaluate the influence of ENSO on atmospheric dynamics using lower and upper tropospheric wind circulation (850 hPa and200 hpa), vertically integrated moisture transport (VIMT), and surface moisture flux (SMF). We have used satellite-based normalised difference vegetation index (NDVI) datasets of the Global Inventory Monitoring and Modeling System (GIMMS) to investigate the impact of ENSO on vegetation dynamics of Haryana and found that NDVI values were higher and lower in case of La Niña and El Niño years, respectively.
42Decoding vegetation resilience: NDVI trends and climate impacts in Indian agriculture.PubMed
Nagaraju Dharavath, Sheshakumar Goroshi
Environ Monit Assess. 2025 Dec 10;198(1):37. doi: 10.1007/s10661-025-14794-w.
The novelty of this study lies in integrating long-term Normalized Difference Vegetation Index (NDVI) fusion datasets with El Niño Southern Oscillation (ENSO)-driven climatic variability to generate policy-oriented, weather-based agro-advisory insights for sustainable agricultural management. This study provides a detailed climatological analysis of NDVI trends across India, covering 40 years of data during the Kharif (1983-2022) and Rabi (1982-2022) seasons. To evaluate long-term vegetation and agricultural productivity dynamics, inter-annual variations of NDVI, food grain productivity, and cumulative rainfall were analyzed for both seasons. The Mann-Kendall trend test, coefficient of variation, and decadal relative deviation analyses were applied to assess long-term vegetation variability. Correlations between NDVI anomalies and Oceanic Niño Index (ONI) values during El Niño and La Niña events were conducted to evaluate ENSO impacts, including the effects of 1- and 2-month lags on seasonal NDVI anomalies. In addition, correlations between rainfall during ENSO events and NDVI were assessed to quantify the influence of ENSO-driven rainfall variability on vegetation dynamics. Results reveal that 82.82% of India shows a positive NDVI trend during Kharif and 80.95% during Rabi. Regions like Rajasthan, Gujarat, and interior Karnataka exhibited high variability in Kharif, while southern Madhya Pradesh and eastern Rajasthan showed pronounced deviations in Rabi. ENSO teleconnections critically influenced vegetation, with El Niño inducing strong NDVI-rainfall correlations in the Western Ghats, Rajasthan, and eastern India during Kharif and in Rayalaseema and Tamil Nadu during Rabi. During El Niño events, correlations between NDVI and ONI in the Kharif season were significant for approximately 6.17% and 7.06% of areas at the 95% and 90% confidence levels, respectively. Kharif season NDVI declined in northeastern India, the Western Ghats, and the southern peninsula but increased in the Deccan Plateau and Indo-Gangetic Plains. The findings highlight the importance of irrigation, afforestation, and adaptive agricultural management in sustaining vegetation health and supporting agromet-advisory services under the Gramin Krishi Mausam Sewa (GKMS) initiative of the India Meteorological Department.
43Wood growth patterns of Macrolobium acaciifolium (Benth.) Benth. (Fabaceae) in Amazonian black-water and white-water floodplain forests.PubMed
Jochen Schöngart, Maria Teresa F Piedade, Florian Wittmann, et al.
Oecologia. 2005 Sep;145(3):454-61. doi: 10.1007/s00442-005-0147-8. Epub 2005 Sep 29.
Macrolobium acaciifolium (Benth.) Benth. (Fabaceae) is a dominant legume tree species occurring at low elevations of nutrient-poor black-water (igapó) and nutrient-rich white-water floodplain forests (várzea) of Amazonia. As a consequence of the annual long-term flooding this species forms distinct annual tree rings allowing dendrochronological analyses. From both floodplain types in Central Amazonia we sampled cores from 20 large canopy trees growing at identical elevations with a flood-height up to 7 m. We determined tree age, wood density (WD) and mean radial increment (MRI) and synchronized ring-width patterns of single trees to construct tree-ring chronologies for every study site. Maximum tree age found in the igapó was more than 500 years, contrary to the várzea with ages not older than 200 years. MRI and WD were significantly lower in the igapó (MRI=1.52+/-0.38 mm year(-1), WD=0.39+/-0.05 g cm(-3)) than in the várzea (MRI=2.66+/-0.67 mm year(-1), WD=0.45+/-0.03 g cm(-3)). In both floodplain forests we developed tree-ring chronologies comprising the period 1857-2003 (n=7 trees) in the várzea and 1606-2003 (n=13 trees) in the igapó. The ring-width in both floodplain forests was significantly correlated with the length of the terrestrial phase (vegetation period) derived from the daily recorded water level in the port of Manaus since 1903. In both chronologies we found increased wood growth during El Niño events causing negative precipitation anomalies and a lower water discharge in Amazonian rivers, which leads to an extension of the terrestrial phase. The climate signal of La Niña was not evident in the dendroclimatic proxies.
44Tropical Indo-Pacific SST influences on vegetation variability in eastern Africa.PubMed
In-Won Kim, Malte F Stuecker, Axel Timmermann, et al.
Sci Rep. 2021 May 17;11(1):10462. doi: 10.1038/s41598-021-89824-x.
Mechanisms by which tropical Pacific and Indian Ocean sea surface temperatures (SST) influence vegetation in eastern Africa have not been fully explored. Here, we use a suite of idealized Earth system model simulations to elucidate the governing processes for eastern African interannual vegetation changes. Our analysis focuses on Tanzania. In the absence of ENSO-induced sea surface temperature anomalies in the Tropical Indian Ocean (TIO), El Niño causes during its peak phase negative precipitation anomalies over Tanzania due to a weakening of the tropical-wide Walker circulation and anomalous descending motion over the Indian Ocean and southeastern Africa. Resulting drought conditions increase the occurrence of wildfires, which leads to a marked decrease in vegetation cover. Subsequent wetter La Niña conditions in boreal winter reverse the phase in vegetation anomalies, causing a gradual 1-year-long recovery phase. The 2-year-long vegetation decline in Tanzania during an ENSO cycle can be explained as a double-integration of the local rainfall anomalies, which originate from the seasonally-modulated ENSO Pacific-SST forcing (Combination mode). In the presence of interannual TIO SST forcing, the southeast African precipitation and vegetation responses to ENSO are muted due to Indian Ocean warming and the resulting anomalous upward motion in the atmosphere.
45Parasite communities of the golden snapper Lutjanus inermis (Perciformes: Lutjanidae): inter-annual variations during strange climatic events.PubMed
Juan Violante-Gonzalez, Princessa J Villalba-Vasquez, Scott Monks, et al.
Folia Parasitol. 2023 Apr 28;70:2023.010. doi: 10.14411/fp.2023.010.
Strange oceanographic events such as El Niño and La Niña may have indirect effects on the local transmission processes of intestinal parasites due to the reduction or increase in populations of potential intermediate or definitive hosts. A total of 713 individuals of Lutjanus inermis (Peters) were collected over an 8-year period (October 2015 to July 2022) from Acapulco Bay, Mexico. Parasite communities in L. inermis were quantified and analysed to determine if they experienced interannual variations in species composition and structure as a result of local biotic and abiotic factors influenced by oceanographic events, such as El Niño-Southern Oscillation (ENSO), or La Niña, the cool phase of the ENSO climate pattern. Twenty-six taxa of metazoan parasites were recovered and identified: two Monogenea, eight Digenea, two Acanthocephala, four Nematoda, one Cestoda, seven Copepoda, and two Isopoda. Species richness at the component community level (8 to 17 species) was similar to reported richness in other species of Lutjanus Bloch. Parasite communities of L. inermis exhibited high inter-annual variation in the abundance of component species of parasite. However, the species richness and diversity were fairly stable over time. Climatic episodes of El Niño and La Niña probably generated notable changes in the structure of local food webs, thus indirectly influencing the transmission rates of intestinal parasite species. Changes in species composition and community structure of parasites possibly were due to variations in feeding behaviour during the events and differences in the host body size.
46An unusually long Rift valley fever inter-epizootic period in Zambia: Evidence for enzootic virus circulation and risk for disease outbreak.PubMed
Herman M Chambaro, Kazuyo Hirose, Michihito Sasaki, et al.
PLoS Negl Trop Dis. 2022 Jun 2;16(6):e0010420. doi: 10.1371/journal.pntd.0010420. eCollection 2022 Jun.
Rift valley fever (RVF) is a mosquito-borne disease of animals and humans. Although RVF outbreaks are usually reported at 5-15-year intervals in sub-Saharan Africa, Zambia has experienced an unusually long inter-epizootic/-epidemic period of more than three decades. However, serological evidence of RVF virus (RVFV) infection in domestic ruminants during this period underscores the need for comprehensive investigation of the mechanisms of virus perpetuation and disease emergence. Mosquitoes (n = 16,778) captured from eight of the ten provinces of Zambia between April 2014 and May 2019 were pooled (n = 961) and screened for RVFV genome by a pan-phlebo RT-PCR assay. Aedes mosquito pools (n = 85) were further screened by nested RT-PCR assay. Sera from sheep (n = 13), goats (n = 259) and wild ungulates (n = 285) were screened for RVFV antibodies by ELISA while genome detection in pooled sera (n = 276) from domestic (n = 248) and wild ungulates (n = 37) was performed by real-time RT-PCR assay. To examine the association between the long inter-epizootic period and climatic variables, we examined El Niño-Southern Oscillation indices, precipitation anomalies, and normalized difference vegetation index. We then derived RVF risk maps by exploring climatic variables that would favor emergence of primary RVFV vectors. While no RVFV genome could be detected in pooled mosquito and serum samples, seroprevalence was significantly high (OR = 8.13, 95% CI [4.63-14.25]) in wild ungulates (33.7%; 96/285) compared to domestic ruminants (5.6%; 16/272). Retrospective analysis of RVF epizootics in Zambia showed a positive correlation between anomalous precipitation (La Niña) and disease emergence. On risk mapping, whilst northern and eastern parts of the country were at high risk, domestic ruminant population density was low (< 21 animals/km2) in these areas compared to low risk areas (>21 animals/km2). Besides evidence of silent circulation of RVFV and the risk of disease emergence in some areas, wildlife may play a role in the maintenance of RVFV in Zambia.
47The effect of ENSO on common bean production in Colombia: a time series approach.PubMed
Hernan Botero, Andrew P Barnes
Food Secur. 2022;14(6):1417-1430. doi: 10.1007/s12571-022-01290-z. Epub 2022 Jun 10.
The common bean is an important staple food in Colombia with diverse nutritional content and environmental benefits. The most important climatic risk confronted by common bean production in Colombia is El Niño Southern Oscillation (ENSO) since its two extreme phases -El Niño and La Niña- increase the intensity and variety of abiotic and biotic stresses in the region. Using information from the Food and Agricultural Organization (FAO) for the period 1991-2018, we test whether pre-2030 ENSO has had a negative impact on common bean production in Colombia using a Prais-Winsten regression model. We find that common beans' yields have been negatively affected by El Niño, but not by La Niña. Moreover, short-run ENSO-induced deviations in the growth rate of precipitation with respect to its long-run value reduce yields and increase farmers' income from common bean production. These results have two important implications. From a modelling standpoint, we find that precipitation has a non-linear relationship with yields and incomes, implying that second-order effects should be incorporated in any analysis of the effects of climatic variables on agricultural production. From a policy perspective, our results suggest a need for countercyclical polices to counteract price spikes of common beans in the Colombian market since, when they occur, they tend to over-compensate the reduction in yields, which reduce common bean consumers' purchasing power and food security.
48El Niño and La Niña differentially drive transmission dynamics of the small ruminant parasite Haemonchus contortus across agroecological zones in Southern Africa.PubMed
Jonathan Henry Ian Tinsley, Eric Rene Morgan
Sci Rep. 2025 Jul 1;15(1):22045. doi: 10.1038/s41598-025-03156-8.
The El Niño La Niña Southern Oscillation (ENSO) exerts a significant influence on agroecological environments and plays a crucial role in influencing crop productivity, yet its impact on animal diseases has been largely overlooked, despite the evident impact of climate on disease transmission. This study aimed to evaluate the impact of ENSO on the transmission potential (Q) of Haemonchus contortus (H. contortus) across agroecological zones (AEZs) in southern Africa across the region's typical rainy season (November-April). Key results indicate that stronger El Niño events can significantly decrease H. contortus transmission potential in subtropical AEZs. Tropical AEZs exhibit lower sensitivity to El Niño generally, but stronger events can lead to significant transmission potential reductions in certain zones. Conversely, La Niña increases transmission potential in tropical AEZs by small-to-medium effect magnitudes, depending on AEZ. Importantly, the analysis found significant increases in Q across direct transitions from El Niño to La Niña, with statistically significant medium effects observed in all tropical AEZs, except for the cool-subhumid AEZ. In subtropical AEZs, notable increases in Q were found in the warm-humid and warm-subhumid zones, also according to medium effect sizes. The study highlights the necessity for disseminating proactive and adaptive animal management practices for small ruminants among smallholder farmers, both during ENSO events and continuing into the post-event transition period, particularly through capacity building, nutritional supplementation and targeted selective treatment. The findings underscore the importance of considering small ruminants in ENSO preparedness and response plans, allowing farmers to optimise the resilience-enhancing roles of small ruminants to mitigate the impacts of climate shocks and food insecurity.
49La Niña weather impacts dietary patterns and dietary diversity among children in the Peruvian Amazon.PubMed
Ramya Ambikapathi, Margaret N Kosek, Gwenyth O Lee, et al.
Public Health Nutr. 2021 Aug;24(11):3477-3487. doi: 10.1017/S1368980020003705. Epub 2020 Oct 27.
OBJECTIVE: In 2011-2012, severe El Niño Southern Oscillation (ENSO) conditions (La Niña) led to massive flooding and temporarily displacement in the Peruvian Amazon. Our aims were to examine the impact of this ENSO exposure on child diets, in particular: (1) frequency of food consumption patterns, (2) the amount of food consumed (g/d), (3) dietary diversity (DD), (4) consumption of donated foods, among children aged 9-36 months living in the outskirts of City of Iquitos in the Amazonian Peru. DESIGN: This was a longitudinal study that used quantitative 24-h recall dietary data collection from children aged 9-36 months from 2010 to 2014 as part of the MAL-ED birth cohort study. SETTING: Iquitos, Loreto, Peru. PARTICIPANTS: Two hundred and fifty-two mother-child dyads. RESULTS: The frequency of grains, rice, dairy and sugar in meals reduced by 5-7 %, while the frequency of plantain in meals increased by 24 % after adjusting for covariates. ENSO exposure reduced girl's intake of plantains and sugar. Despite seasonal fluctuations in the availability of fruits, vegetables and fish, DD remained constant across seasons and as children aged. However, DD was significantly reduced under moderate La Niña conditions by 0·32 (P < 0·05) food groups. Adaptive social strategies such as consumption of donated foods were significantly higher among households with girls. CONCLUSIONS: This is the first empirical study to show differential effect of the ENSO on the dietary patterns of children, highlighting differences by gender. Public health nutrition programmes should be climate- and gender-sensitive in their efforts to safeguard the diets of vulnerable populations.
50Effects of atmospheric systems operating in the Northeast of Brazil on the volumes of artificial reservoirs.PubMed
Rafaela Dos Santos Gomes, Kellen Carla Lima, Felipe Jeferson de Medeiros
Sci Rep. 2025 Jul 30;15(1):27783. doi: 10.1038/s41598-024-82858-x.
This study aims to quantify the impact of rainfall patterns influenced by the seasonal movement of the Intertropical Convergence Zone (ITCZ), Frontal Systems (FS), and South Atlantic Convergence Zone (SACZ) during El Niño, La Niña, and neutral years on reservoirs water volumes across the Northeast of Brazil (NEB) from 1998 to 2018. Data sources include meridional and zonal components of the winds, outgoing longwave radiation, monthly rainfall, oceanic sea surface temperature, and reservoir volume from the Brazilian National Agency for Water and Basic Sanitation and state departments were used. ITCZ identification employed semi-objective techniques, while CPTEC/INPE reports aided in identifying FS and SACZ. The study calculated reservoir water volume percentages and applied correspondence analysis between volume changes and atmospheric systems during El Niño, La Niña, and neutral years. The results show that when the ITCZ central position during February-May is near (far) equator positive (negative) rainfall anomalies occurred, correlating with increase (decrease) reservoir volumes. El Niño (La Niña) years consistently exhibited negative (positive) rainfall anomalies, with reservoirs volume decreasing (increasing) its water storage. Approximately 17% of FS in Brazil reaches the southern NEB during November-February, with an average of three FS and SACZ cases per season in this region. Increase (decrease) in the reservoirs volume was observed when the FS and SACZ was above average. Overall, although the statistical tests indicates that there was no statistical significance, the correspondence analysis indicated a potential visual connection between the meteorological systems, reservoir volumes and ENSO phases. Furthermore, we highlighted the importance of analyzing other hydrological variables such as evapotranspiration and surface runoff to better comprehend the NEB reservoir recharge dynamics in ENSO phases.
51Improved drought monitoring in teleconnection to the climatic escalations: A hydrological modeling based approach.PubMed
Sonam Sandeep Dash, Bhabagrahi Sahoo, Narendra Singh Raghuwanshi
Sci Total Environ. 2023 Jan 20;857(Pt 2):159545. doi: 10.1016/j.scitotenv.2022.159545. Epub 2022 Oct 18.
Catchment-scale efficient agricultural drought monitoring and irrigation planning mostly depend on the accuracy of evapotranspiration (ET) estimates under different crop-growth phases. As indirect ET estimation under limited data availability scenario and complex paddy-field dynamics could not be sufficiently addressed by the conventional curve number (CN) based SWAT model, SWAT incorporates an add-in pothole module (SWAT-P) that conceptualizes the paddy-field hydrology with the empirical coefficient or equations resulting in poor ET estimates. To address these limitations, this study integrates an improved pothole methodology in SWAT (SWAT-EP) accounting the vadose-zone soil water dynamics under alternate ponding and drying conditions, ET variation under moisture abundant and stress conditions, and role of irrigation return flow generated in the paddy fields. The proposed approach was validated in the Kangsabati River integrated reservoir-catchment-command (12,014.70 km) of the eastern India, and the results reveal that SWAT-EP outperformed the existing SWAT-P in reproducing the catchment-scale streamflow and ET flux with respect to the FAO-56 Penman-Monteith (PM) based ET estimates in all the four cropping seasons. The SWAT-EP derived Standardized Evapotranspiration Drought Index (SEDI) based drought severity and duration well-corroborate with the benchmark MOD16A2 derived drought estimates; whereas, the SWAT-P tends to overestimate the drought severity in the command area. The predictive uncertainty in drought monitoring was the lowest by SWAT-EP with relatively lower uncertainty was observed in the crop-growing locations of Kharagpur and Mohanpur. Moreover, the teleconnection between drought and climatic escalations corresponds to a better reproducibility of El Niño and La Niña phases by the SWAT-EP, while the SWAT-P performed un-satisfactorily across different spatiotemporal domains. This study endorses to adopt the proposed SWAT-EP model for river basin-scale drought monitoring and irrigation planning with prior validation in the diversified climatic and topographic conditions.
52Epidemiological Investigation of a Diarrhea Outbreak in the South Pacific Island Nation of Tuvalu During a Severe La Niña-Associated Drought Emergency in 2011.PubMed
Jordan P Emont, Albert I Ko, Avanoa Homasi-Paelate, et al.
Am J Trop Med Hyg. 2017 Mar;96(3):576-582. doi: 10.4269/ajtmh.16-0812. Epub 2017 Apr 6.
The association between heavy rainfall and an increased risk of diarrhea has been well established but less is known about the effect of drought on diarrhea transmission. In 2011, the Pacific island nation of Tuvalu experienced a concurrent severe La Niña-associated drought and large diarrhea outbreak. We conducted a field investigation in Tuvalu to identify factors that contributed to epidemic transmission in the context of a drought emergency. Peak case numbers coincided with the nadir of recorded monthly rainfall, the lowest recorded since 1930. Independent factors associated with increased risk of diarrhea were households with water tank levels below 20% (odds ratio [OR] = 2.31; 95% confidence interval = 1.16-4.60) and decreased handwashing frequency (OR = 3.00 [1.48-6.08]). The resolution of the outbreak occurred after implementation of a hygiene promotion campaign, despite persistent drought and limited water access. These findings are potentially important given projections that future climate change will cause more frequent and severe droughts.
53Crop variety management for climate adaptation supported by citizen science.PubMed
Jacob van Etten, Kauê de Sousa, Amílcar Aguilar, et al.
Proc Natl Acad Sci U S A. 2019 Mar 5;116(10):4194-4199. doi: 10.1073/pnas.1813720116. Epub 2019 Feb 19.
Crop adaptation to climate change requires accelerated crop variety introduction accompanied by recommendations to help farmers match the best variety with their field contexts. Existing approaches to generate these recommendations lack scalability and predictivity in marginal production environments. We tested if crowdsourced citizen science can address this challenge, producing empirical data across geographic space that, in aggregate, can characterize varietal climatic responses. We present the results of 12,409 farmer-managed experimental plots of common bean ( L.) in Nicaragua, durum wheat ( Desf.) in Ethiopia, and bread wheat ( L.) in India. Farmers collaborated as citizen scientists, each ranking the performance of three varieties randomly assigned from a larger set. We show that the approach can register known specific effects of climate variation on varietal performance. The prediction of variety performance from seasonal climatic variables was generalizable across growing seasons. We show that these analyses can improve variety recommendations in four aspects: reduction of climate bias, incorporation of seasonal climate forecasts, risk analysis, and geographic extrapolation. Variety recommendations derived from the citizen science trials led to important differences with previous recommendations.
54Extreme precipitation events and increased risk of campylobacteriosis in Maryland, U.S.A.PubMed
Sutyajeet Soneja, Chengsheng Jiang, Crystal Romeo Upperman, et al.
Environ Res. 2016 Aug;149:216-221. doi: 10.1016/j.envres.2016.05.021. Epub 2016 May 20.
Consumption of contaminated poultry, raw milk and water are significant risk factors for Campylobacter infection. Previous studies also have investigated the association between weather (temperature and precipitation) and increased risk of campylobacteriosis, but limited information exists regarding the impacts of extreme heat and precipitation events on campylobacteriosis risk, and how such risk may differentially impact coastal communities. We obtained Campylobacter case data 2002-2012; n=4804) from the Maryland Foodborne Diseases Active Surveillance Network (FoodNet). We identified extreme heat and extreme precipitation events during this time (2002-2012) using location and calendar day specific thresholds (95th percentile for extreme heat and 90th percentile for extreme precipitation) that were computed based on a 30-year baseline (1960-1989). We linked these datasets using GIS and used negative binomial generalized estimating equations adjusted for demographic confounders to calculate the association between exposure to extreme events and risk of campylobacteriosis in Maryland. We observed that a one-day increase in exposure to extreme precipitation events was associated with a 3% increase in risk of campylobacteriosis in coastal areas of Maryland (Incidence Rate Ratio (IRR): 1.03, 95% confidence interval (CI): 1.01, 1.05), but such an association was not observed in noncoastal areas. Furthermore, the risk associated with extreme precipitation events was considerably higher during La Niña periods (IRR: 1.09, 95% CI: 1.05, 1.13), while there was no evidence of elevated risk during El Niño or ENSO Neutral periods. Exposure to extreme heat events was not associated with an increased risk of campylobacteriosis, except during La Niña periods (IRR: 1.04, 95% CI: 1.01, 1.08). Extreme precipitation events could result in flooding within coastal areas that may bring water contaminated with bacterial pathogens (originating from sources such as septic systems, municipal wastewater treatment plants and concentrated animal feeding operations) into close proximity with individuals, where frequency of contact may be higher.
55Role of extreme weather events and El Niño Southern Oscillation on incidence of Enteric Fever in Ahmedabad and Surat, Gujarat, India.PubMed
Veena Iyer, Ayushi Sharma, Divya Nair, et al.
Environ Res. 2021 May;196:110417. doi: 10.1016/j.envres.2020.110417. Epub 2020 Nov 17.
INTRODUCTION: Enteric Fever (EF) affects over 14.5 million people every year globally, with India accounting for the largest share of this burden. The water-borne nature of the disease makes it prone to be influenced as much by unsanitary living conditions as by climatic factors. The detection and quantification of the climatic effect can lead to improved public health measures which would in turn reduce this burden. METHODOLOGY: We obtained a list of monthly Widal positive EF cases from 1995 to 2017 from Ahmedabad and Surat Municipalities. We obtained population data, daily weather data, and Oceanic Niño Index values from appropriate sources. We quantified the association between extreme weather events, phases of El Niño Southern Oscillations (ENSO) and incidence of EF. RESULTS: Both cities showed a seasonal pattern of EF, with cases peaking in early monsoon. Risk of EF was affected equally in both cities by the monsoon season -- Ahmedabad (35%) and Surat (34%). Extreme precipitation was associated with 5% increase in EF in Ahmedabad but not in Surat. Similarly, phases of ENSO had opposite effects on EF across the two cities. In Ahmedabad, strong El Niño months were associated with 64% increase in EF risk while strong La Niña months with a 41% reduction in risk. In Surat, strong El Niño was associated with 25% reduction in risk while moderate La Niña with 21% increase in risk. CONCLUSIONS: Our results show that the risk of EF incidence in Gujarat is highly variable, even between the two cities only 260 kms apart. In addition to improvements in water supply and sewage systems, preventive public health measures should incorporate variability in risk across season and phases of ENSO. Further studies are needed to characterize nationwide heterogeneity in climate-mediated risk, and to identify most vulnerable populations that can benefit through early warning systems.
56Climate change and dengue risk in central region of Thailand.PubMed
Uma Langkulsen, Kamol Promsakha Na Sakolnakhon, Nigel James
Int J Environ Health Res. 2020 Jun;30(3):327-335. doi: 10.1080/09603123.2019.1599100. Epub 2019 Mar 28.
Dengue poses a huge public health threat. It places physical and financial burden on individuals affected, family, and national health systems. This descriptive study aimed for two specific objectives; to investigate the weather effects on dengue incidence and to estimate level of risk in the central region of Thailand. It utilized a 10-year population level dengue morbidity data and meteorological data from 2007 to 2016. Kriging method was used to interpolate a weighted risk factor upon a 5-point risk estimate was developed for estimating area risk on a 5-point scale. The findings showed that 2 out of 16 provinces (12.5%) are strong to very strong risk areas for dengue, including Bangkok and Nonthaburi provinces. The study revealed that the impact of La Niña and El Niño on increased dengue incidence and risk level in Bangkok. We recommend further studies to establish intersections of dengue disease and social determinants of health.
57Effects of temperature, rainfall, and El Niño Southern Oscillations on dengue-like-illness incidence in Solomon Islands.PubMed
Gerry Andhikaputra, Yu-Han Lin, Yu-Chun Wang
BMC Infect Dis. 2023 Apr 6;23(1):206. doi: 10.1186/s12879-023-08188-x.
BACKGROUND: This study investigated associations between climate variables (average temperature and cumulative rainfall), and El Niño Southern Oscillation (ENSO) and dengue-like-illness (DLI) incidence in two provinces (Western and Guadalcanal Provinces) in Solomon Islands (SI). METHODS: Weekly DLI and meteorological data were obtained from the Ministry of Health and Medical Services SI and the Ministry of Environment, Climate Change, Disaster Management and Meteorology from 2015 to 2018, respectively. We used negative binomial generalized estimating equations to assess the effects of climate variables up to a lag of 2 months and ENSO on DLI incidence in SI. RESULTS: We captured an upsurge in DLI trend between August 2016 and April 2017. We found the effects of average temperature on DLI in Guadalcanal Province at lag of one month (IRR: 2.186, 95% CI: 1.094-4.368). Rainfall had minor but consistent effect in all provinces. La Niña associated with increased DLI risks in Guadalcanal Province (IRR: 4.537, 95% CI: 2.042-10.083), whereas El Niño associated with risk reduction ranging from 72.8% to 76.7% in both provinces. CONCLUSIONS: Owing to the effects of climate variability and ENSO on DLI, defining suitable and sustainable measures to control dengue transmission and enhancing community resilience against climate change in low- and middle-developed countries are important.
58Environmental Changes and the Impact on the Human Infections by Dengue, Chikungunya and Zika Viruses in Northern Brazil, 2010-2019.PubMed
Robson Dos Santos Souza Marinho, Rodrigo Lopes Sanz Duro, Mânlio Tasso de Oliveira Mota, et al.
Int J Environ Res Public Health. 2022 Oct 3;19(19):12665. doi: 10.3390/ijerph191912665.
Environmental changes are among the main factors that contribute to the emergence or re-emergence of viruses of public health importance. Here, we show the impact of environmental modifications on cases of infections by the dengue, chikungunya and Zika viruses in humans in the state of Tocantins, Brazil, between the years 2010 and 2019. We conducted a descriptive and principal component analysis (PCA) to explore the main trends in environmental modifications and in the cases of human infections caused by these arboviruses in Tocantins. Our analysis demonstrated that the occurrence of El Niño, deforestation in the Cerrado and maximum temperatures had correlations with the cases of infections by the Zika virus between 2014 and 2016. El Niño, followed by La Niña, a gradual increase in precipitation and the maximum temperature observed between 2015 and 2017 were shown to have contributed to the infections by the chikungunya virus. La Niña and precipitation were associated with infections by the dengue virus between 2010 and 2012 and El Niño contributed to the 2019 outbreak observed within the state. By PCA, deforestation, temperatures and El Niño were the most important variables related to cases of dengue in humans. We conclude from this analysis that environmental changes (deforestation and climate change) presented a strong influence on the human infections caused by the dengue, chikungunya and Zika viruses in Tocantins from 2010 to 2019.
59Seasonally lagged effects of climatic factors on malaria incidence in South Africa.PubMed
Takayoshi Ikeda, Swadhin K Behera, Yushi Morioka, et al.
Sci Rep. 2017 May 29;7(1):2458. doi: 10.1038/s41598-017-02680-6.
Globally, malaria cases have drastically dropped in recent years. However, a high incidence of malaria remains in some sub-Saharan African countries. South Africa is mostly malaria-free, but northeastern provinces continue to experience seasonal outbreaks. Here we investigate the association between malaria incidence and spatio-temporal climate variations in Limpopo. First, dominant spatial patterns in malaria incidence anomalies were identified using self-organizing maps. Composite analysis found significant associations among incidence anomalies and climate patterns. A high incidence of malaria during the pre-peak season (Sep-Nov) was associated with the climate phenomenon La Niña and cool air temperatures over southern Africa. There was also high precipitation over neighbouring countries two to six months prior to malaria incidence. During the peak season (Dec-Feb), high incidence was associated with positive phase of Indian Ocean Subtropical Dipole. Warm temperatures and high precipitation in neighbouring countries were also observed two months prior to increased malaria incidence. This lagged association between regional climate and malaria incidence suggests that in areas at high risk for malaria, such as Limpopo, management plans should consider not only local climate patterns but those of neighbouring countries as well. These findings highlight the need to strengthen cross-border control of malaria to minimize its spread.
60El Niño and other climatic drivers of epidemic malaria in Ethiopia: new tools for national health adaptation plans.PubMed
Adugna Woyessa, Asher Siebert, Aisha Owusu, et al.
Malar J. 2023 Jun 24;22(1):195. doi: 10.1186/s12936-023-04621-3.
BACKGROUND: Ethiopia has a history of climate related malaria epidemics. An improved understanding of malaria-climate interactions is needed to inform malaria control and national adaptation plans. METHODS: Malaria-climate associations in Ethiopia were assessed using (a) monthly climate data (1981-2016) from the Ethiopian National Meteorological Agency (NMA), (b) sea surface temperatures (SSTs) from the eastern Pacific, Indian Ocean and Tropical Atlantic and (c) historical malaria epidemic information obtained from the literature. Data analysed spanned 1950-2016. Individual analyses were undertaken over relevant time periods. The impact of the El Niño Southern Oscillation (ENSO) on seasonal and spatial patterns of rainfall and minimum temperature (Tmin) and maximum temperature (Tmax) was explored using NMA online Maprooms. The relationship of historic malaria epidemics (local or widespread) and concurrent ENSO phases (El Niño, Neutral, La Niña) and climate conditions (including drought) was explored in various ways. The relationships between SSTs (ENSO, Indian Ocean Dipole and Tropical Atlantic), rainfall, Tmin, Tmax and malaria epidemics in Amhara region were also explored. RESULTS: El Niño events are strongly related to higher Tmax across the country, drought in north-west Ethiopia during the July-August-September (JAS) rainy season and unusually heavy rain in the semi-arid south-east during the October-November-December (OND) season. La Niña conditions approximate the reverse. At the national level malaria epidemics mostly occur following the JAS rainy season and widespread epidemics are commonly associated with El Niño events when Tmax is high, and drought is common. In the Amhara region, malaria epidemics were not associated with ENSO, but with warm Tropical Atlantic SSTs and higher rainfall. CONCLUSION: Malaria-climate relationships in Ethiopia are complex, unravelling them requires good climate and malaria data (as well as data on potential confounders) and an understanding of the regional and local climate system. The development of climate informed early warning systems must, therefore, target a specific region and season when predictability is high and where the climate drivers of malaria are sufficiently well understood. An El Niño event is likely in the coming years. Warming temperatures, political instability in some regions, and declining investments from international donors, implies an increasing risk of climate-related malaria epidemics.
61Temporal and spatial patterns of malaria reinfection in northeastern Venezuela.PubMed
R Barrera, M E Grillet, Y Rangel, et al.
Am J Trop Med Hyg. 1999 Nov;61(5):784-90. doi: 10.4269/ajtmh.1999.61.784.
We stratified the risk of malaria transmission (Plasmodium vivax) in 35 villages along a coastal range in northeastern Venezuela (51 km2) where the main vector is the mosquito Anopheles aquasalis. After 20 years without local malaria transmission, reinfection of the entire area occurred from May to December 1985 by local (continuous) and jump (discontinuous) dispersal. Epidemiologic, environmental, and vector variables were investigated with the aid of a Geographic Information System. Risk factors for malaria transmission were human population density, proximity to pre-adult mosquito habitats (< 500 m), and the number of pre-adult habitats nearby. Most inhabitants, immature mosquito habitats, and malaria cases were located at low elevations and on gentle slopes. High prevalence of malaria during the dry seasons was associated with the presence of permanent bodies of water containing An. aquasalis. Occurrence of a La Niña event in 1988 (wet and cool phase of the El Niño Southern Oscillation) triggered malaria transmission to unusually high levels, consolidating infection in the area, and rendering traditional control efforts useless. We recommend tracking malaria persistence per village and associated risk factors as methods to reduce the cost of malaria control programs.
62Effect of El Niño Southern Oscillation cycle on the potential distribution of cutaneous leishmaniasis vector species in Colombia.PubMed
Mariano Altamiranda-Saavedra, Juan David Gutiérrez, Astrid Araque, et al.
PLoS Negl Trop Dis. 2020 May 28;14(5):e0008324. doi: 10.1371/journal.pntd.0008324. eCollection 2020 May.
Local anomalies in rainfall and temperature induced by El Niño and La Niña episodes could change the structure of the vector community. We aimed to estimate the effect of the El Niño-La Niña cycle in the potential distribution of cutaneous leishmaniasis (CL) vector species in Colombia and to compare the richness of the vectors with the occurrence of CL in the state of Norte de Santander. The potential distributions of four species were modeled using a MaxEnt algorithm for the following episodes: La Niña 2010-2011, Neutral 2012-2015 and El Niño 2015-2016. The relationship between the potential richness of the vectors and the occurrence of CL in Norte de Santander was evaluated with a log-binomial regression model. During the El Niño 2015-2016 episode, Lutzomyia ovallesi and Lutzomyia panamensis increased their distribution into environmentally suitable areas, and three vector species (Lutzomyia gomezi, Lutzomyia ovallesi and Lutzomyia panamensis) showed increases in the range of their altitudinal distribution. During the La Niña 2010-2011 episode, a reduction was observed in the area suitable for occupation by Lutzomyia gomezi and Lutzomyia spinicrassa. During the El Niño 2015-2016 episode, the occurrence of at least one CL case was related to a higher percentage of rural localities showing a richness of vectors = 4. The anomalies in rainfall and temperature induced by the episodes produced changes in the potential distribution of CL vectors in Colombia. In Norte de Santander, during Neutral 2012-2015 and El Niño 2015-2016 episodes, a higher probability of at least one CL case was related to a higher percentage of areas with a greater richness of vectors. The results help clarify the effect of the El Niño-La Niña cycle in the dynamics of CL in Colombia and emphasize the need to monitor climate variability to improve the prediction of new cases.
63Decade-long deep-ocean warming detected in the subtropical South Pacific.PubMed
Denis L Volkov, Sang-Ki Lee, Felix W Landerer, et al.
Geophys Res Lett. 2017 Jan 28;44(2):927-936. doi: 10.1002/2016GL071661. Epub 2017 Jan 18.
The persistent energy imbalance at the top of the atmosphere, inferred from satellite measurements, indicates that the Earth's climate system continues to accumulate excess heat. As only sparse and irregular measurements of ocean heat below 2000 m depth exist, one of the most challenging questions in global climate change studies is whether the excess heat has already penetrated into the deep ocean. Here we perform a comprehensive analysis of satellite and in situ measurements to report that a significant deep-ocean warming occurred in the subtropical South Pacific Ocean over the past decade (2005-2014). The local accumulation of heat accounted for up to a quarter of the global ocean heat increase, with directly and indirectly inferred deep ocean (below 2000 m) contribution of 2.4 ± 1.4 and 6.1-10.1 ± 4.4%, respectively. We further demonstrate that this heat accumulation is consistent with a decade-long intensification of the subtropical convergence, possibly linked to the persistent La Niña-like state.
64Near-term tropical cyclone risk and coupled Earth system model biases.PubMed
Adam H Sobel, Chia-Ying Lee, Steven G Bowen, et al.
Proc Natl Acad Sci U S A. 2023 Aug 15;120(33):e2209631120. doi: 10.1073/pnas.2209631120. Epub 2023 Aug 7.
Most current climate models predict that the equatorial Pacific will evolve under greenhouse gas-induced warming to a more El Niño-like state over the next several decades, with a reduced zonal sea surface temperature gradient and weakened atmospheric Walker circulation. Yet, observations over the last 50 y show the opposite trend, toward a more La Niña-like state. Recent research provides evidence that the discrepancy cannot be dismissed as due to internal variability but rather that the models are incorrectly simulating the equatorial Pacific response to greenhouse gas warming. This implies that projections of regional tropical cyclone activity may be incorrect as well, perhaps even in the direction of change, in ways that can be understood by analogy to historical El Niño and La Niña events: North Pacific tropical cyclone projections will be too active, North Atlantic ones not active enough, for example. Other perils, including severe convective storms and droughts, will also be projected erroneously. While it can be argued that these errors are transient, such that the models' responses to greenhouse gases may be correct in equilibrium, the transient response is relevant for climate adaptation in the next several decades. Given the urgency of understanding regional patterns of climate risk in the near term, it would be desirable to develop projections that represent a broader range of possible future tropical Pacific warming scenarios-including some in which recent historical trends continue-even if such projections cannot currently be produced using existing coupled earth system models.
65Robust impact of tropical Pacific SST trends on global and regional circulation in boreal winter.PubMed
Joonsuk M Kang, Rhidian Thomas, Nick Dunstone, et al.
NPJ Clim Atmos Sci. 2025;8(1):315. doi: 10.1038/s41612-025-01192-9. Epub 2025 Aug 27.
Evidence has emerged of a discrepancy in tropical Pacific sea surface temperature (SST) trends over the satellite era, where most coupled climate models struggle to simulate the observed La Niña-like SST trends. Here we highlight wider implications of the tropical Pacific SST trend discrepancy for global circulation trends during boreal winter, using two complementary methods to constrain coupled model SST trends: conditioning near-term climate prediction (hindcast) simulations, and pacemaking coupled climate simulations. The robust circulation trend response to constraining the tropical Pacific SST trend resembles the interannual La Niña response. Constraining tropical Pacific SST robustly reduces tropical tropospheric warming, improving agreement with reanalyses, and moderately shifts the zonal-mean jets poleward. It also improves surface air temperature and precipitation trends in ENSO-sensitive regions, such as the Americas, South Asia, and southern Africa. Our results underline the importance of tropical Pacific SST for achieving confidence in multidecadal model projections.
66Contribution of anthropogenic aerosols to persistent La Niña-like conditions in the early 21st century.PubMed
Yen-Ting Hwang, Shang-Ping Xie, Po-Ju Chen, et al.
Proc Natl Acad Sci U S A. 2024 Jan 30;121(5):e2315124121. doi: 10.1073/pnas.2315124121. Epub 2024 Jan 22.
The discrepancy between the observed lack of surface warming in the eastern equatorial Pacific and climate model projections of an El Niño-like warming pattern confronts the climate research community. While anthropogenic aerosols have been suggested as a cause, the prolonged cooling trend over the equatorial Pacific appears in conflict with Northern Hemisphere aerosol emission reduction since the 1980s. Here, using CESM, we show that the superposition of fast and slow responses to aerosol emission change-an increase followed by a decrease-can sustain the La Niña-like condition for a longer time than expected. The rapid adjustment of Hadley Cell to aerosol reduction triggers joint feedback between low clouds, wind, evaporation, and sea surface temperature in the Southeast Pacific, leading to a wedge-shaped cooling that extends to the central equatorial Pacific. Meanwhile, the northern subtropical cell gradually intensifies, resulting in equatorial subsurface cooling that lasts for decades.
67Dynamics for El Niño-La Niña asymmetry constrain equatorial-Pacific warming pattern.PubMed
Michiya Hayashi, Fei-Fei Jin, Malte F Stuecker
Nat Commun. 2020 Aug 28;11(1):4230. doi: 10.1038/s41467-020-17983-y.
The El Niño-Southern Oscillation (ENSO) results from the instability of and also modulates the strength of the tropical-Pacific cold tongue. While climate models reproduce observed ENSO amplitude relatively well, the majority still simulates its asymmetry between warm (El Niño) and cold (La Niña) phases very poorly. The causes of this major deficiency and consequences thereof are so far not well understood. Analysing both reanalyses and climate models, we here show that simulated ENSO asymmetry is largely proportional to subsurface nonlinear dynamical heating (NDH) along the equatorial Pacific thermocline. Most climate models suffer from too-weak NDH and too-weak linear dynamical ocean-atmosphere coupling. Nevertheless, a sizeable subset (about 1/3) having relatively realistic NDH shows that El Niño-likeness of the equatorial-Pacific warming pattern is linearly related to ENSO amplitude change in response to greenhouse warming. Therefore, better simulating the dynamics of ENSO asymmetry potentially reduces uncertainty in future projections.
68Salinity anomaly as a trigger for ENSO events.PubMed
Jieshun Zhu, Bohua Huang, Rong-Hua Zhang, et al.
Sci Rep. 2014 Oct 29;4:6821. doi: 10.1038/srep06821.
According to the classical theories of ENSO, subsurface anomalies in ocean thermal structure are precursors for ENSO events and their initial specification is essential for skillful ENSO forecast. Although ocean salinity in the tropical Pacific (particularly in the western Pacific warm pool) can vary in response to El Niño events, its effect on ENSO evolution and forecasts of ENSO has been less explored. Here we present evidence that, in addition to the passive response, salinity variability may also play an active role in ENSO evolution, and thus important in forecasting El Niño events. By comparing two forecast experiments in which the interannually variability of salinity in the ocean initial states is either included or excluded, the salinity variability is shown to be essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate salinity observations with large-scale spatial coverage.
69Climate Variability and Infectious Disease Burden in Coastal Sindh, Pakistan: A Trend Analysis (2019-2022).PubMed
Hira Tariq, Aamir Alamgir, Zakir Punar, et al.
Int J Infect Dis. 2025 Nov 22:108225. doi: 10.1016/j.ijid.2025.108225.
OBJECTIVE: This study examines the spatio-temporal trends of climate-sensitive infectious diseases and their associations with climate variables in coastal districts of Sindh, Pakistan from 2019 to 2022. METHODS: An ecological time-series design was used to analyzed facility-level surveillance data from 166 primary health centers alongside meteorological data on temperature, humidity, and precipitation from ground-based monitors. Incidence rates for suspected malaria, diarrhea, dysentery, and typhoid were calculated. Temporal trends were assessed using the Mann-Kendall test, and Pearson correlations were used to examine associations with climate variables. RESULTS: A total of 982,538 cases were recorded over the four-year period, with under-five diarrhea and suspected malaria being the most prevalent. Thatta district alone reported nearly 30,000 malaria cases in September 2022 following severe monsoon flooding. Malaria peaked 4-6 weeks after monsoon rainfall, while diarrhea showed dual peaks in March and during monsoon months. Significant positive correlations were found between disease incidence and temperature, humidity, and precipitation, particularly for malaria and diarrhea. CONCLUSION: The study provides compelling evidence of the impact of climate variability on infectious disease patterns in coastal Sindh highlighting the need for climate-resilient health systems, enhanced disease surveillance, and integration of meteorological data into early-warning mechanisms.
72Associations between apparent temperatures and emergency ambulance calls in Wuxi, China: a time series analysis.PubMed
Chao Yang, Xiuzhu Li, Wanjun Zhang, et al.
Front Public Health. 2025 Sep 9;13:1652961. doi: 10.3389/fpubh.2025.1652961. eCollection 2025.
Inappropriate apparent temperature (AT) is a major global threat to human health. Although the association between temperature and health has been studied extensively, limited evidence regarding emergency ambulance calls (EACs) is available. Daily emergency department visit records, meteorological data, and air pollutant data were obtained from 1 January 2014 to 31 December 2019. A distributed lag non-linear model was applied to examine the interaction between AT and lagged effects. The analysis was stratified according to disease aetiology, sex, and age. The proportion of EACs attributable to AT was calculated as an indicator of associated burden. A non-linear U-shaped relationship was observed between AT and non-accidental, cardiovascular, and circulatory EACs, with the lowest risk AT occurring at 22.54 °C, 17.12 °C, and 12.74 °C, respectively. High AT effects manifested immediately, whereas low AT effects were delayed. Stratified analysis indicated that males and individuals aged ≥65 years demonstrated heightened sensitivity to both extreme heat (97.5th percentile, 35.98 °C) and cold (2.5th percentile, -1.27 °C), whereas females displayed greater vulnerability to extreme heat [relative risks = 1.16, 95% confidence intervals (CI): 1.04-1.29]. The attributable fraction (AF) for non-accidental EACs in Wuxi was 6.88% (95% CI: 4.09-9.26%), with higher AFs observed for cardiovascular (10.37%) and respiratory (4.94%) emergencies. Moderate thermal variations substantially affected the EACs more than extreme AT conditions. These findings underscore the necessity of implementing early warning mechanisms targeting thermal extremes and developing temperature-regulated public facilities to safeguard vulnerable groups, particularly older citizens, during extreme temperature events.
73Meteorological factors association with under-five children diarrhea incidence in central Gondar zone, Northwest Ethiopia. A time series study.PubMed
Gelila Yitageasu, Hailemariam Feleke, Zewudu Andualem, et al.
BMC Res Notes. 2025 May 9;18(1):208. doi: 10.1186/s13104-025-07270-8.
BACKGROUND: Under 5 children diarrhea has been one of the major public health concerns in countries with limited resources such as Ethiopia. Understanding the association between under-5 diarrhea and meteorological factors will contribute to safeguarding children from adverse health effects through early warning mechanisms. Thus, this study aimed to explore the association between under-5 diarrhea and meteorological factors to reduce health risks. METHODS: A time-series ecological study was used to explore the association between meteorological factors and under-5 diarrhea incidence. Spearman's correlation was computed to test the correlation and a negative binomial regression model was fitted to determine the associations of meteorological factors with under-5 diarrhea incidence. The multicollinearity was checked using the variance inflation factor (VIF) before the multivariable regression analysis and the value was 5. aIRRs with 95% CIs and a significance level of 0.05 were used for all the statistical tests. Statistical analyses were conducted using STATA 14.2 software. RESULTS: The highest under-5 diarrhea incidence morbidities was 180.9 per 1000 per year for under-five children. This study revealed a positive and negative correlation between the count of under-5 diarrhea and average monthly temperature and rainfall at 0 and 2 lag months with RRs of 1.0209 (95% CI: 1.0034-1.0387), RR 1.0202(95% CI:1.0022-1.0385), RR 0.999(95% CI:0.9985-0.9996), and RR 0.9992(95% CI:0.9987-0.9997) respectively. CONCLUSION: There was an association between under 5 diarrhea incidence and meteorological factors in the Central Gondar Zone. The mean monthly temperature and rainfall were positively and negatively related to the incidence of diarrhea in children under 5 years old. The results showed that the observed association between meteorological factors and under-5 diarrhea incidence could be used as evidence for the use of early warning systems for the prevention of childhood diarrhea.
74Impact of Airborne Pollen on Allergic Rhinitis and Asthma in an Arid Chinese City: A Time-Series Study from Lanzhou.PubMed
Guangyu Zhai, Chongchang Feng, Wenjuan Zhou
Int Arch Allergy Immunol. 2025 Dec 5:1-25. doi: 10.1159/000549815.
Airborne pollen has emerged as a critical environmental driver of allergic respiratory diseases, particularly under the accelerating influence of global climate change. This study investigates the short-term effects of daily airborne pollen concentrations on the incidence of allergic rhinitis (AR) and bronchial asthma (BA) in Lanzhou, a representative arid city in northwestern China. Utilizing outpatient visit data from a Class A tertiary hospital between April and October 2024, along with daily records of pollen concentrations, meteorological indicators, and air pollutant levels, we employed a Distributed Lag Non-linear Model (DLNM) to examine the non-linear and lagged relationships between pollen exposure and disease risk. Our findings reveal a significant association between elevated pollen levels and increased risks of both AR and BA, with the strongest effects observed within 1-3 days after exposure. Stratified analyses show that females and individuals aged 0-19 years are particularly susceptible. Moreover, health impacts were more pronounced during the late summer to autumn pollen season, likely due to the presence of highly allergenic species such as Artemisia and Chenopodiaceae. Thunderstorm events were also found to coincide with spikes in pollen concentrations and disease incidence, suggesting a potential link to thunderstorm-related allergic exacerbations. These results underscore the urgent need for region-specific pollen monitoring systems, early warning mechanisms, and targeted public health interventions to mitigate the burden of allergic respiratory diseases in vulnerable populations, particularly under increasingly volatile climatic conditions.