伴随南海夏季风爆发的大尺度大气环流演变

Large Scale Atmospheric Circulation Evolutions Associated with Summer Monsoon Onset in the South China Sea

主要基于美国ＮＣＥＰ和ＮＣＡＲ的再分析资料（１９８０～１９９６ 年），针对南海夏季风爆发日期进行合成分析， 研究了伴随南海夏季风爆发的大尺度大气环流演变。其结果清楚地表明伴随南海夏季风爆发， 南亚和东南亚地区的对流层低层风场、对流层高层位势高度场以及大气湿度场和垂直运动场都有极显著的变化。南亚和东南亚８５０ ｈＰａ 上涡旋对的发展和活动以及５００ ｈＰａ 副高从南海地区的东撤对南海季风爆发起着重要作用。伴随南海夏季风的爆发， 在孟加拉湾到南中国海一带整层湿度和５００ ｈＰａ 垂直上升运动都出现了极明显的增加。对流层高层和对流层低层环流演变的特征也清楚表明， 南海夏季风爆发既是全球环流冬夏演变的一个部分， 又有显著的区域性特征。本文还指出南海夏季风在北部比中部和南部早建立的结论依据不足， 进而补充给出了亚洲季风爆发日期示意图。

Mainly by using NCEP/NCAR reanalysis data (1980～1996), the large scale atmospheric circulation evolutions associated with summer monsoon onset in the South China Sea are studied based on the composite analyses corresponding to the onset dates The results clearly show that there are very evident variations of the atmospheric circulation (especially in South Asia and Southeast Asia) associated with the summer monsoon onset in the South China Sea, such as the wind field in the lower troposphere, the geopotential height field in the upper troposphere, the humidity and vertical velocity fields in South Asia and Southeast Asia The development and activity of the vortex pair at 850 hPa in South Asia and Southeast Asia regions and the withdraw eastwards of the subtropical high from the South China Sea play an important role in the onset of summer monsoon in the South China Sea There are also evident increases of the integrated humidity and vertical velocity at 500 hPa in the Bay of Bengal to the South China Sea area associated with the outbreak of summer monsoon in the South China Sea region The atmospheric circulation evolutions show that the onset of summer monsoon in the South China Sea region is a part of global circulation evolution from winter to summer and also it has regional abnormal feature It is still indicated that the onset of summer monsoon in the northern South China Sea is not earlier than that in the southern South China Sea The schematic diagram on the onset dates of the Asian summer monsoon before June is also shown