中文摘要：

根据1979-2004年NCEP/NCAR的逐日OLR资料,对南海夏季风爆发前后南海地区热带深对流的纬向和经向传播特征进行分析,结果表明,在南海夏季风爆发前后,热带深对流的传播方向无论是纬向还是经向在各年都不尽相同,亦即具有多向性。在纬向上,南海季风区深对流既可以由孟加拉湾向东传播到南海,也可以由西太平洋向西传播到南海,也可在南海地区直接生成。但在此时期,印度季风区纬向传播相对单一,主要为向西传播。在经向上,南海地区的对流活动可以受到来自南半球热带地区和北半球中纬度的共同影响,但印度季风区主要受热带地区对流的影响。上述结果表明,南海夏季风爆发期季风区对流活动远比印度季风区复杂,南海夏季风爆发的深对流云系既可来源于其东西侧,也可来源于其南北侧,或是局地发展。作者进一步分析了造成不同深对流来源的机制,发现低空副高不同的移动路径是造成这一多样性的可能原因,这可能也是目前对部分年份南海夏季风爆发日期确定存在争议的原因。

英文摘要：

Based on the daily outgoing long-wave radiation （OLR） dataset from NCEP/NCAR during 1979 - 2004, the features of the zonal and meridional propagations of the tropical convection during the onset period of the South China Sea （SCS） summer monsoon （SCSSM） are analyzed in this paper. Results indicate that the directions of both the zonal propagation and the meridional counterpart are quite different. For example, for the zonal propagation, the deep convection can propagate either from the Bay of Bengal （BOB） to SCS, or from the western Pacific to SCS, or developed locally. But during the onset period of the Indian summer monsoon, the zonal propagation is relatively simplex with a westward propagation. For the meridional direction, the convection over SC~ can be influenced by both the counterpart from the tropical regions of the Southern Hemisphere and from the middle latitudes of the Northern Hemisphere. But in the Indian monsoon regions, the convection comes only from the Southern Hemi- sphere. These observation results reveal that the convective activities during the onset period of SCSSM are more complex than those of the Indian summer monsoon. Results also show that the different retreat ways of the western Pacific subtropical high in the lower troposphere can lead to the multi-direction propagation of the deep convection over SCS. This will misrepresent the judgment of the onset dates of SCSSM.