Hydrodynamics of regional and seasonal variations in Congo Basin precipitation
Hydrodynamics of regional and seasonal variations in Congo Basin precipitation
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DOI：
10.1007/s00382-021-06066-3
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发表时间：
2021-09
期刊：
影响因子：
4.6
通讯作者：
K. Cook;E. Vizy
中科院分区：
文献类型：
--
作者：
K. Cook;E. Vizy
利用大气柱水分收支对决定刚果盆地降水季节性的过程进行了研究。研究刚果盆地降水季节性的基本决定因素有助于对所有时间尺度上的变化进行基于过程的研究，包括与温室气体引起的全球变暖有关的变化。ERA5再分析产生的降水分布为该分析提供了足够的精度，这需要一个一致的数据集来将大气动力学和湿度分布与降水场联系起来。刚果盆地的北半球和南半球区域被分开检查，以避免误解刚果盆地降雨主要是双峰的。在刚果盆地，虽然蒸散发对于向大气柱提供水分以支持降水是必不可少的，但它的季节变化很小，不驱动降水的季节性。在春分季节，降水主要是由800-500 hPa层湿润环境中的经向风辐合支持的，湿润空气流入赤道槽。在两个半球，北方秋雨比北方春雨强，因为低层水汽辐散在北方春雨中发展，与发展中的撒哈拉热低压有关。夏季，水汽辐合项在两个半球的水汽收支中也占主导地位，850-500 hPa层的经向辐合为跨赤道气流与安哥拉和撒哈拉热低压附近的气旋气流相互作用。冬季降水偏少的原因是来自冬季副热带高压的干燥空气对大陆的平流。
The processes that determine the seasonality of precipitation in the Congo Basin are examined using the atmospheric column moisture budget. Studying the fundamental determinants of Congo Basin precipitation seasonality supports process-based studies of variations on all time scales, including those associated with greenhouse gas-induced global warming. Precipitation distributions produced by the ERA5 reanalysis provide sufficient accuracy for this analysis, which requires a consistent dataset to relate the atmospheric dynamics and moisture distribution to the precipitation field. The Northern and Southern Hemisphere regions of the Congo Basin are examined separately to avoid the misconception that Congo Basin rainfall is primarily bimodal. While evapotranspiration is indispensable for providing moisture to the atmospheric column to support precipitation in the Congo Basin, its seasonal variations are small and it does not drive precipitation seasonality. During the equinoctial seasons, precipitation is primarily supported by meridional wind convergence in the moist environment in the 800–500 hPa layer where moist air flows into the equatorial trough. Boreal fall rains are stronger than boreal spring rains in both hemispheres because low-level moisture divergence develops in boreal spring in association with the developing Saharan thermal low. The moisture convergence term also dominates the moisture budget during the summer season in both hemispheres, with meridional convergence in the 850–500 hPa layer as cross-equatorial flow interacts with the cyclonic flow about the Angola and Sahara thermal lows. Winter precipitation is low because of dry air advection from the winter hemisphere subtropical highs over the continent.