El Nio期间印度洋海温异常对亚洲气候的影响

Influence of the Indian Ocean SSTA on Asian Climate during an ENSO Period

ElNin～o事件发生时 ,赤道东太平洋海温出现高达 2～ 3℃的正异常 ,同时 ,印度洋海温也会出现异常。但每次ElNin～o事件期间 ,印度洋异常海温的结构是不相同的 ,翘翘板型的海表温度结构 ,是印度洋海温异常的一种典型分布。利用IAP -GCM 9L模式 ,我们对ElNin～o期间 ,印度洋东冷西暖异常海温分布对气候的影响 ,特别是对亚洲气候的影响 ,作了数值模拟研究。模拟研究的结果表明 ,印度洋海温主要影响孟加拉湾、中南半岛、印尼、印度次大陆及中国大陆南部地区的气候变化。在ElNin～o发生期间 ,东冷西暖的印度洋海温结构 ,加大了东太平洋海温异常给东亚季风区带来的影响 ,它使中南半岛到印尼更加干旱 ,中国华北到山东半岛的降水减少 ,而使中国西南到华南的降水明显增加。在其影响下 ,东亚地区的雨带呈纬向分布 ,形成旱涝相间的纬向带状异常分布型 ,使模式模拟结果与中国旱涝的实际分布更加接近。同时 ,在对高度场、流场的分析中可以看到 ,印度洋东冷西暖海温分布使夏季副高位置偏南 ,印度洋到南海的西南风减弱 ,在中国西南到华南为气旋性环流控制 ,这些特征与降水分布是一致的。模拟试验表明 ,印度洋海温异常对我国ElNin～o期间降水异常的分布型有重要影响。

During the ENSO event period, the Indian Ocean SST will be anomalous almost simultaneously. But the spatial structure of the SSTA in the Indian Ocean varies from time to time. The seesaw structure is a typical pattern of the Indian Ocean SSTA. Based on the IAP-GCM 9L model developed in the Institute of Atmospheric Physics, Chinese Academy of Sciences, the SSTA pattern with a warm SST in the western Indian Ocean and a cold SST in the East Indian Ocean was simulated during an ENSO period. And its effect on the Asian climate was studied. The results indicate that the Indian Ocean SSTA would mainly influence the climates of Bengal, Indo-China, Indonesia, India and China. During the ENSO period, the SSTA pattern with warm west and a cold east SST in the Indian Ocean will enhance the climate anomalousness brought by the eastern Pacific Ocean SSTA. Especially, it makes Indo-China drier and reduces the precipitation over the northern China. But it obviously increases the precipitation over the area from southwest China to southeast China. So, the precipitation will be concentrated in a zonal region around the Changjiang River drainage area and forms zonal drought and flood pattern which is close to the fact. Therefore, during ENSO period, the Indian Ocean SSTA is important to Asian climate especially to the anomalous precipitation pattern of China.