关于南海夏季风建立的大尺度特征及其机制的讨论

使用1998年南海季风试验期间高质量资料和NCEP/NCAR40年再分析资料分析了南海季风建立前后的大尺度环流特征和要素的突变及爆发过程。发现南亚高压迅速地从菲律宾以东移到中南半岛北部，印缅槽加强，赤道印度洋西风加强并向东向北迅速扩展和传播，以及相伴随的中低纬相互作用和西太平洋副高连续东撤是南海夏季风建立的大尺度特征，与此同时，亚洲低纬地区的南北温差和纬向风切变也发生相应的突变。数值实验结果指出，印度半岛地形的陆面加热作用在其东侧激发的气旋性环流对于印缅槽的加强有重要作用，并进而有利于南海夏季风先于印度夏季风爆发。

Large Scale Features of SCS Summer Monsoon Onset and Its Possible Mechanism

The high quality dataset from the SCS (South China Sea) Monsoon Experiment and 40-year NCEP/NCAR reanalysis data are used to investigate the large scale features and abrupt change in meteorological elements during the onset of the SCS summer monsoon. It is found that the SCS summer monsoon establishment is characterized by the South Asian High migrating swiftly from the eastern side of Philippines to the northern part of Indo-China Peninsula and the enhancement of the Indian-Burma trough and equatorial westerly over the Indian Ocean associated with the equatorial westerly expanding towards northeastward, and followed by the mid-low latitude interaction and continuous retreat eastward of the western Pacific subtropical high. Further study shows that the meridional temperature difference and the zonal wind vertical shear over the Asian lower latitudes also experience abrupt change during the onset of the SCS summer monsoon. Numerical results reveal that the Indian Peninsula acts as a critical role for the enhancement of the Indian-Burma trough with a cyclonic difference circulation excited to the east side of the peninsula through ground sensible heating in such a way that the SCS summer monsoon occurs prior to the Indian summer monsoon.