Song Fengfei, Dong Hongqiang, Wu Lixin, Leung L Ruby, Lu Jian, Dong Lu, Wu Peili, Zhou Tianjun
Frontier Science Center for Deep Ocean Multispheres and Earth System and Physical Oceanography Laboratory, Ocean University of China, Qingdao, China.
Laoshan Laboratory, Qingdao, China.
Nat Commun. 2025 Mar 4;16(1):2188. doi: 10.1038/s41467-025-57501-6.
Tropical land generally experiences the hottest period (spring) in a year just before the onset of wet season. Previous studies suggested that in a warming climate, the wet season would come later, but its origin is debated and its impact on temperature remains unknown. Here, we find that the warming of hot season would be amplified under global warming, and refer to it as "hot-season-gets-hotter" phenomenon. The amplified hot season warming is closely tied to the amplified warming of hot temperature percentiles. The hot-season-gets-hotter phenomenon is mainly due to the rainfall delay and most evident in the Amazon, where spring is warming by almost 1 K more than the annual mean and the 99th percentile temperatures are warming ~30% more than the mean by the end of 21st century in a high emission scenario. Comparing experiments with and without land-atmosphere coupling, it is further found that the rainfall delay is initially driven by the enhanced effective atmospheric heat capacity and then substantially amplified by positive soil moisture-atmosphere feedback. In the satellite period, observations consistently show that the hot-season-gets-hotter phenomenon has already emerged along with the rainfall delay in the Amazon. Intensified hot and dry spring climate can enhance risks of drought, heatwaves and wildfires, threatening the Amazon forest and habitats in the tropics.
热带地区通常在雨季开始前经历一年中最热的时期（春季）。以往的研究表明，在气候变暖的情况下，雨季会来得更晚，但其成因存在争议，且其对气温的影响尚不清楚。在此，我们发现全球变暖会加剧热季的升温，并将其称为“热季变热”现象。热季升温加剧与高温百分位数的升温加剧密切相关。“热季变热”现象主要是由于降雨延迟，在亚马逊地区最为明显，在高排放情景下，到21世纪末，该地区春季升温比年平均气温高出近1开尔文，第99百分位温度比平均温度高出约30%。通过对比有和没有陆气耦合的实验，进一步发现降雨延迟最初是由有效大气热容量增强驱动的，然后通过正的土壤湿度-大气反馈大幅放大。在卫星观测期，观测结果一致表明，“热季变热”现象已经在亚马逊地区随着降雨延迟出现。春季炎热干燥气候加剧会增加干旱、热浪和野火风险，威胁亚马逊森林和热带地区的栖息地。
