Predictability Analysis and Preliminary Application of the Bay of Bengal Summer Monsoon Onset
Predictability Analysis and Preliminary Application of the Bay of Bengal Summer Monsoon Onset
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发表时间：
2004
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通讯作者：
Wu Guo-xiong
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作者：
Wu Guo-xiong
本文从热-风关系出发，根据夏季风爆发的实质是海陆热力对比变化的结果，研究了副热带高压变化与季风爆发的关系。夏季风爆发首先出现在孟加拉湾东部（BOB），然后到六月初定期向东传播到西太平洋。当该轴到达某一地区时，当地低层风向和上层纬向温度梯度（MTG）符号发生变化，季风爆发。此外，所需的时间来推翻MTG取决于初始MTG以及季风爆发前的平均纬向加热差。在此基础上，利用1980 - 1999年3 - 5月NCEP/NCAR再分析逐日和逐月资料，探讨了BOB季风爆发的可预报性。结果表明，利用初始MTG和气候平均纬向温差变化对孟加拉湾季风爆发进行定性预报是可能的。青藏高原春季月平均气温与BOB夏季风爆发存在显著的相关关系。这为预测季风爆发提供了额外的线索。利用这两种方法对2000年和2001年的BOB季风爆发进行了定性预报。然而，详细的检查表明，一个令人满意的预测BOB季风爆发需要考虑的低频变率的大气环流。
Based on thermal-wind relation and the fact that the essence of summer monsoon onset is a result of the change in land-sea thermal contrast, the relation between monsoon onset and the variation of the subtropical anticyclone is studied. The summer monsoon onset appears firstly over the eastern Bay of Bengal (BOB), then propagates regularly eastwards to the western Pacific by early June. Whenever the axis arrives at a region, the in situ lower-layer wind direction and the sign of meridional temperature gradient (MTG) in the upper-layer are changed, and monsoon onset occurs. Furthermore, the time required to overturn the MTG depends on the initial MTG as well as the averaged meridional differential heating before the monsoon onset. Based on these results, the daily and monthly NCEP/NCAR reanalysis data during March to May 1980\_1999 were used to explore the predictability of the BOB monsoon onset. Results show that qualitative prediction of the BOB monsoon onset is possible by using the initial MTG and the climate mean meridional differential temperature variations. Moreover, there is significant correlation between the spring-time monthly-mean air temperature over Qinghai-Xizang Plateau and the BOB summer monsoon onset. This provides additional clue for predicting the monsoon onset. These two methods have been utilized to predict the qualitative BOB monsoon onset in 2000 and 2001 correctly. However, detailed examination reveals that a satisfactory prediction of the BOB monsoon onset requires the consideration of the low-frequency variability of the atmospheric circulation.