Itterly Kyle F, Taylor Patrick C, Dodson Jason B, Tawfik Ahmed B
Science Systems and Applications, Inc. Hampton Virginia USA.
Climate Science Branch NASA Langley Research Center Hampton Virginia USA.
J Geophys Res Atmos. 2016 Jul 27;121(14):8186-8208. doi: 10.1002/2016JD025039. Epub 2016 Jul 19.
Climate and reanalysis models contain large water and energy budget errors over tropical land related to the misrepresentation of diurnally forced moist convection. Motivated by recent work suggesting that the water and energy budget is influenced by the sensitivity of the convective diurnal cycle to atmospheric state, this study investigates the relationship between convective intensity, the convective diurnal cycle, and atmospheric state in a region of frequent convection-the Amazon. Daily, 3-hourly satellite observations of top of atmosphere (TOA) fluxes from Clouds and the Earth's Radiant Energy System Ed3a SYN1DEG and precipitation from Tropical Rainfall Measuring Mission 3B42 data sets are collocated with twice daily Integrated Global Radiosonde Archive observations from 2002 to 2012 and hourly flux tower observations. Percentiles of daily minimum outgoing longwave radiation are used to define convective intensity regimes. The results indicate a significant increase in the convective diurnal cycle amplitude with increased convective intensity. The TOA flux diurnal phase exhibits 1-3 h shifts with convective intensity, and precipitation phase is less sensitive. However, the timing of precipitation onset occurs 2-3 h earlier and the duration lasts 3-5 h longer on very convective compared to stable days. While statistically significant changes are found between morning atmospheric state and convective intensity, variations in upper and lower tropospheric humidity exhibit the strongest relationships with convective intensity and diurnal cycle characteristics. Lastly, convective available potential energy (CAPE) is found to vary with convective intensity but does not explain the variations in Amazonian convection, suggesting that a CAPE-based convective parameterization will not capture the observed behavior without incorporating the sensitivity of convection to column humidity.
气候和再分析模型在热带陆地存在大量的水分和能量收支误差，这与昼夜强迫的湿对流的错误表征有关。鉴于最近的研究表明水分和能量收支受对流昼夜循环对大气状态的敏感性影响，本研究调查了对流强度、对流昼夜循环和大气状态在对流频繁的亚马逊地区之间的关系。利用2002年至2012年每日两次的综合全球探空仪档案观测数据以及每小时的通量塔观测数据，将来自云和地球辐射能量系统Ed3a SYN1DEG的每日3小时一次的大气顶（TOA）通量卫星观测数据和热带降雨测量任务3B42数据集的降水数据进行了匹配。用每日最低出射长波辐射的百分位数来定义对流强度状态。结果表明，随着对流强度的增加，对流昼夜循环振幅显著增大。TOA通量昼夜相位随对流强度呈现1 - 3小时的偏移，而降水相位的敏感性较低。然而，与稳定日相比，在对流非常强烈的日子里，降水开始时间提前2 - 3小时，持续时间延长3 - 5小时。虽然在早晨大气状态和对流强度之间发现了具有统计学意义的变化，但对流层上下湿度的变化与对流强度和昼夜循环特征的关系最为密切。最后，发现对流有效位能（CAPE）随对流强度而变化，但无法解释亚马逊对流的变化，这表明基于CAPE的对流参数化在不考虑对流对气柱湿度敏感性的情况下无法捕捉到观测到的行为。
