Influence of Indian Ocean SST regionality on the East African short rains
Influence of Indian Ocean SST regionality on the East African short rains
复制标题
DOI：
10.1007/s00382-020-05265-8
复制
发表时间：
2020-04-28
期刊：
影响因子：
4.6
通讯作者：
Vizy, Edward K.
中科院分区：
文献类型：
--
作者：
Liu, Weiran;Cook, Kerry H.;Vizy, Edward K.
确定了海温在年际尺度上对赤道东非短雨有显著影响的印度洋三个次区域，并利用天气研究和预报模式(WRF)的区域气候模式模拟研究了这种影响的物理过程。产生了五个20年的集合积分，以表示控制气候，并模拟SSTA在有影响的地区的单独和综合影响。西印度洋的SSTA对赤道东非短雨的影响比印度洋中部和东部的SSTA更大，无论是在显着变化的降水复盖率上还是在降水响应的大小上。积极的西印度洋SSTA显著增加了赤道东非地区(东经30度-40度，S 5度-北纬5度)95%以上的短时降水，而该地区只有30%的地区对印度洋中部和东部的SSTA做出了反应。分析中没有发现有影响的印度洋偶极子模式的证据。利用大气水汽收支和湿静态能量分析，参考Gill模式中的Kelvin和Rossby波产生，但在存在复杂地形和非零背景流的情况下，诊断了这种影响的机制。潮湿环境中的风辐合异常在所有情况下都主要支持降水异常，而大气不稳定的变化在很大程度上受低层水汽的控制。印度洋中部和东部SSTA改变了当地的环流和降水，但对东非的远程影响弱于西印度洋SSTA。
Three sub-regions of the Indian Ocean in which SSTs significantly influence the equatorial East African short rains on interannual timescales are identified, and the physical processes of this influence are studied using regional climate model simulations from the Weather Research and Forecasting model (WRF). Five 20-year ensemble integrations are generated to represent a control climate and to simulate the individual and combined effects of SSTAs in the influential regions. SSTAs in the western Indian Ocean exert a stronger influence on the equatorial East African short rains than central and eastern Indian Ocean SSTAs both in terms of the coverage of significantly-changed precipitation and the magnitude of the precipitation response. Positive western Indian Ocean SSTAs significantly increase the short rains over 95% of the equatorial East Africa domain (30 degrees-40 degrees E, 5 degrees S-5 degrees N), while only 30% of the region responds to central and eastern Indian Ocean SSTAs. Evidence of an influential Indian Ocean dipole mode does not emerge from the analysis. The mechanisms of this influence are diagnosed using atmospheric moisture budget and moist static energy analyses, with reference to Kelvin and Rossby wave generation as in the Gill model, but in the presence of complicated topography and nonzero background flows. Wind convergence anomalies in a moist environment primarily support precipitation anomalies in all cases, while changes in atmospheric instability are largely controlled by low-level moisture. Central and eastern Indian Ocean SSTAs change circulations and precipitation locally, but the remote influence on East Africa is weaker than that of the western Indian Ocean SSTAs.