青藏高原云-辐射-加热效应和南亚夏季风--1985年与1987年对比分析

文中首先利用NCEP NCAR再分析的风场资料 ,分析了南亚夏季风的时空特征 ,选取了有代表性的典型强、弱夏季风年 ,继而利用ISCCP C2、ERBE S4卫星观测资料和NCEP NCAR再分析资料 ,对比分析了强、弱夏季风前期青藏高原地区的云—辐射—加热状况及其在海、陆差异中的作用。分析结果表明 ,南亚夏季风强或弱 ,其前期青藏高原地区的云—辐射—加热效应有明显的差异。在强 (弱 )南亚夏季风的前期 ,青藏高原大部分地区为相对少 (多 )云区 ,其云量变化不仅表明了此区的云—辐射—加热效应的不同 ,更重要的是与此同时出现的海、陆之间云量分布的“跷跷板”现象 ,进一步改变了海、陆之间的热力差异。而且 ,在强南亚夏季风年 ,这种热力差异不但开始得早 ,而且持续时间长、作用范围大 ,从而对南亚夏季风的形成和变化产生重要的影响

CLOUD-RADIATION-HEATING EFFECT OVER THE TIBETAN PLATEAU AND SUMMER MONSOON OF THE SOUTH ASIAN

In this paper, the years of strong and weak South Asian summer monsoon are chosen by the EOF analysis of the NCEP/NCAR wind data. And then the cloud-radiation-heating state over the Tibetan Plateau in the early days (April-May) of the strong and the weak South Asian summer monsoon is analyzed and its effect on sea-land thermal contrast is discussed by using the ISCCP C2, ERBE S4 satellite observation data and the NCEP/NCAR data. Results show that differences between the early days of the strong and the weak South Asian summer monsoon in cloud-radiation-heating state and effect are obvious. In the early days of the strong South Asian summer monsoon, there is relatively less cloud cover over most areas of the Tibetan Plateau, the short wave radiation cloud-forcing is little. Accordingly, the net radiation flux of the earth-atmosphere system is increased and the earth-atmosphere system is heated. During the same time, the difference between temperate latitude and tropical zone is negative for the cloud cover anomalies and that is positive for the net radiation anomalies, the sea-land thermal contrast is intensified. But in the early days of the weak South Asian summer monsoon, the cloud-radiation-heating state and effect are contrary to the strong case. It is evident that the cloud-radiation-heating state over the Tibetan Plateau in the early days of the South Asian summer monsoon plays a very important role in activities of the South Asian summer monsoon.