索马里急流变异及其与东亚夏季风和中国降水异常的关系

Variation of Somali jet and its impact on East Asian summer monsoon and associated China rainfall anomalies

利用近50 a大气再分析资料、海表温度分析资料和我国降水观测资料,分析揭示了索马里急流的年际和年代际变异及其与东亚夏季风和我国夏季降水异常的关系。结果表明:在年际时间尺度上,夏季索马里急流增强,对应ENSO冷事件,马斯克林高压增强,澳大利亚高压减弱,东部越赤道气流减弱,东亚夏季风增强,我国夏季北方降水偏多,南方降水偏少;反之亦然。然而,在年代际时间尺度上,夏季索马里急流增强,对应PDO暖位相,马斯克林高压和澳大利亚高压均增强,东部越赤道气流增强,而东亚夏季风减弱,我国夏季东北、西北和长江流域降水偏多,而华北、华南和西南地区降水偏少;反之亦然。

This study describes the variation of Somali jet and its impact on the East Asian summer monsoon and associated China rainfall anomalies with the atmospheric reanalysis data and rainfall records in China for 1951-2005. Main results are as follows. At the interannual timescale, the enhanced Somali jet is corresponding to the weakened cross equatorial flows （CEFs） of other channels, the developing La Nina event and the intensified East Asian summer monsoon, resulting in increased precipitation in northern China and reduced precipitation in southern China; and vice versa. However, at the interdecadal ti- mescale, the enhanced Somali jet is corresponding to the intensified CEFs of other channels, the warm PDO event and the weakened East Asian summer monsoon, resulting in reduced precipitation in northern, southern and southwestern China and increased precipitation in northeastern, northwestern China and Yangtze River valley; and vice versa.