印度洋海温异常年际变率模态对中国东部地区夏季降水影响机制的数值试验

利用ECHAM5全球大气环流模式研究了印度洋海温异常年际变率模态从冬至夏的演变对我国东部地区夏季降水影响的机制。观测资料研究表明:对于正的印度洋海温异常年际变率模态,春、夏季热带印度洋和澳大利亚以西洋面(东极子)均为水汽的异常源区,向马达加斯加以东南洋面(西极子)及印度洋邻近大陆提供水汽。夏季,印度洋地区南极涛动、马斯克林高压加强;而印度季风低压和南亚高压均减弱,对应于印度夏季风减弱。夏季印度洋地区正压性的纬向风异常经向遥相关使热带印度洋地区出现西风异常,导致海洋性大陆地区对流活动减弱,而菲律宾海地区对流活动加强,进而导致西太平洋副热带高压偏弱、位置偏东北。对于负的印度洋海温异常年际变率模态,则反之。模式结果基本支持了已有的观测资料诊断结果。

Simulating the Mechanism of the Interannual Variability Mode of the Indian Ocean Sea Surface Temperature Anomalies Impacting on the Summer Rainfall over Eastern China

The ECHAM5 atmospheric general circulation model was used to study how the evolution of the interannual variability mode (IVM) of the Indian Ocean sea surface temperature anomalies (SSTA) from winter to summer influence summer rainfall over eastern China. Observations show that, for positive IVM, the tropical Indian Ocean and the region west of Australia (the west pole) are an anomalous source of water vapor in spring and summer, and provide the water vapor for the region southeast of Madagascar (the east pole) and the continents surrounding the Indian Ocean. In summer, the intensity of Antarctic Oscillation (AAO) over the Indian Ocean region and the Mascarene High increase, whereas the Indian monsoon trough and the South Asia High decrease, which indicates that the Indian summer monsoon circulation weakens. The meridional atmospheric teleconnection of zonal wind anomalies in the Indian Ocean causes westerly anomalies in the tropical Indian Ocean, which depress convective activities over the Maritime Continent but enhance them over the Philippine Sea during summer. This makes the western Pacific subtropical high decrease and shift northeastward. For negative IVM, the observations are the opposite. The model results basically support the abovementioned observations.