1998年南海夏季风爆发前环流的三维海流诊断计算的研究

基于1998年南海夏季风爆发前航次(4月22日至5月24日)获得的水文资料和NCEP提供的风场资料,采用三维海流诊断模式计算南海环流,结合同时期高度计资料T/P推得的水位高度距平分布,获得了一致的南海环流的流态,主要环流特性概括如下:(1)黑潮入侵南海较弱,黑潮的大部分绕过吕宋海峡作反气旋弯曲,向东北方向流向台湾以东,但小部分在300m以浅向西入侵,并局限于中国大陆以南较狭窄的陆架坡内,不扩展到所有的西边界,这与Qu的观点一致.(2)南海北部环流,在300m以浅主要由海盆尺度的气旋环流支配,它以两个气旋式涡C1与C2为核心组成.在300m以深,南海北部环流被反气旋环流以暖涡W4为核心分离成两个尺度不大、分别以气旋涡C2和C3为核心的环流.冬季时海盆尺度气旋式环流的范围比4~5月大得多.(3)南海中部环流,主要由海盆尺度的反气旋环流支配.在300m以浅海盆尺度的反气旋式环流分别以暖涡W1,W2和W3为核心组成.在反气旋式涡W1东南存在一个以C1为核心气旋式环流.但在300m以深,海盆尺度的反气旋环流分别以暖涡W1,W2和W4为核心组成,并向北扩展到20°N.(4)在越南以东近岸存在一支较强的沿岸北向流,其强度比6月时沿岸的北向流强.这支较强的北向的沿岸流一直可达17°15'N附近,比6月时更往北大约3°15'.(5)产生1998年4~5月南海环流的动力机制有两个:最重要的动力因子为斜压场与地形相互作用项,其次为东南风作用下风应力与地形相互作用项.Sverdrup关系在南海环流不满足.

A three dimensional diagnostic modeling study of the South China Sea circulation before onset of summer monsoon in 1998

On the basis of the wind data from NCEP and the hydrographic data obtained on 22 April~24 May 1998, the circulation in the South China Sea(SCS) are computed by the three dimensional diagnostic model.The combination of SSH Aderived from T/Paltimeter and numerical results provides a consistent circulation pattern for the SCS, and the main circulation features can be summarized as follows: (1) The Kuro shio intrusion weakens and the pathway of the most of Kuroshio by passes.However, a part of Kuro-shiointrudes west ward above 300 m levels.This west ward intruded flow is located narrowly confined in the continental slope south of China above 300 m levels and does not appear to follow the western boundary throug hout,which agrees with the viewpoint of Qu et al.(2) The basinOscalecy clonicgy redominates in the northern SCS and consists of two cyclonic eddies C2 and C3 above 300 m levels.However, it is separated into two parts by ananti Ocycloniceddy W4 below 300 m levels.The scope of the basinOscale cyclonicgyre is wider in winter than that in the cruise 1.(3) The basinOscale antiOcy clonic gyredominates in the central SCS and consists of the three antiOcyclonic eddies W1, W2 and W3 above 300 m levels.However,below 300 m levels it consists of the anti-Ocy clonic eddies W1, W2 and W4 and extends northward to near 20°N.The cold eddy C1 exists southeast of the antiOcy clonic eddy W1.(4) A northward coastal jetis present at the western boundary near the coast of Vietnamat depths above the 300 m level, and develops northward more far about the distance 3b15c N than that in the cruise 2.(5) Most important dynamical mechanism is because of the joint effect of the baroclinity and relief (JEBAR).The second dynamical mechanism is because of the interaction between the wind stress and relief (IBWSR) under the southeasterly wind.The Sverdrup' relation can not been satisfied in the SCS.