1998年夏季季风爆发前后南海环流的多涡特征

利用南海季风实验（SCSMEX－IOP1、IOP2）期间（1998年4月底－7月初）所获得的温盐深（CTD）、声学多普勒流速剖面仪（ADCP）资料及TOPEX／POSEIDON卫星高度计遥感资料，分析了南海表层、1．0MPa层和3．0MPa层得力势异常场的分布格局，探讨了夏季季风爆发前后南海的环流特征。结果表明：在夏季季风爆发前（IOP1期间）南海北部以气旋试流动为主，并在此气旋式环流的东部镶嵌着一个较小的反气旋型涡；南海中部和南部以反气旋式流动为主，其中越南以东海域存在着两个南北对峙分布的反气旋型涡，在它们的东侧伴随一气旋型涡。季风爆发后（IPO2期间），南海北部仍然以气旋式流动为主，黑潮水越过巴士海峡南北中线，一部分可能入侵南海北部，另一部分向东北折回黑潮主干；南海中部和南部仍以反气旋式流动为主，越南以东海域北部的反气旋型涡消失，但南西的反气旋型涡加强，与IOP1类似，仍伴随着一个气旋型涡。总体而方，强流区出现在巴士海峡西北侧和南海西部（尤其是越东南东沿岸），南海东部和东南部为弱流区。

MULTI-EDDY FEATURES OF SOUTH CHINA SEA CIRCULATION AROUND ONSET OF SUMMER MONSOON IN 1998

Distributions of geopotential anomaly in the surface, 1.0 MPa and 3.0 MPa layers of the South China Sea (SCS) are analyzed using CTD data obtained on SCSMEX cruises of IOP1 and IOP2 (from late April to early July, 1998). ADCP observation data and satellite altimeter data from TOPEX/POSEITON are also used to reveal circulation features of the SCS around the onset of summer monsoon. The results show that, before the monsoon onset (during IOP1), circulation of the northern SCS was mainly cyclonic, with a smaller anticyclone eddy embedded in its eastern side. Circulation in central and southern SCS, however, was mainly anticyclonic. Two anticyclonic eddies were located along the Vietnam coast, accompanied by a cyclone further east. The northern SCS was still controlled by cyclonic circulation after the onset of summer monsoon (during IOP2). The results show that Kuroshio water extended across the Bashi Channel. It is likely that part of it intruded into the northern SCS, and the remaining turned northeast and returned to the Kuroshio. The circulation maintained generally anticyclonic in central and southern SCS, but the northern anticyclone off Vietnam disappeared while the southern anticyclone, still accompanied by a cyclone further east, strengthened. In general, strong currents occured in the areas northwest to the Bashi Channel and the western SCS (especially along the southeastern coast of Vietnam). Currents in the eastern and southeastern SCS were generally weak.