2000年夏季南海环流的改进逆方法计算

Calculation of circulation in the South China Sea during the summer of 2000 by the modified inverse method

基于2000年8月航次在南海调查资料,采用改进逆方法,并结合TOPEX/ERS分析的SSH分布,获得以下的主要结果:(1)南海中部和西南部环流系统主要受反气旋环流所支配.主要有越南东南反气旋涡W1,其水平尺度约为300km,垂向深度可达1000m以深,流速很强,其最大流速为79cm/s左右,还有暖涡W2以及吕宋岛西南反气旋涡环流系统W3.其次,在反气旋涡W1与W2之间还存在气旋式涡C1.其水平尺度比暖涡W1小得多,流速也较强.两涡W1与C1之间存在一支南向流,它们组成一个准偶极子.(2)在暖涡W1的西侧存在西边界流,即北向射流,其流速很强,约在12°N流向转向东北.(3)南海北部环流系统主要受气旋环流所支配.在断面N2附近及以北存在一个气旋式环流系统.其次,在海南岛东南存在一个尺度不大的反气旋环流系统.(4)南海东南部环流系统主要受气旋环流所支配.主要有在巴拉望岛以西存在尺度较大的气旋环流系统,以及暖涡W1东南存在一个气旋环流系统.其次,在加里曼丹岛西北还存在范围不大的反气旋环流.(5)比较1998年夏季航次与2000年夏季航次时计算结果,虽然它们在定量上有些变化与差别,但在定性上它们的环流结构有十分相似之处.这表明,南海环流具有明显的季节特性.(6)比较2000年夏季南海水文结构,流函数分布以及TOPEX/ERS的SSH分布。

On the basis of hydrographic data obtained in August 2000 cruise, the circulation in the South China Sea (SCS) is computed by using the modified inverse method in combination with SSH data from TOPEX/ERS-2 Analysis. The following results have been obtained. (1) The central and southwestern SCSs are dominated mainly by anticyclonic circulation systems. They are mainly as follows. 1) There is strong anticyclonic eddy southeast of Vietnam (W_1). Its horizontal scale is about (300 km), and it extends vertically from the surface to the (1 000 m) more than. It is very strong with a V_(max) of about (79 cm/s); 2)there are a warm eddy W_2 and the anticyclonic circulation system W_3 west off the Philippines. In the next place, there is a stronger cyclonic eddy C_1 between the anticyclonic eddies W_1 and W2, and it is also strong.A southward flow exists between the eddies W_1 and C_1.The eddies W_1 and C_1 compose a quasi-dipole. (2) A strong coastal jet is present at the western boundary west of an anticyclonic eddy W_1, and the jet flows northward and separates from the coast of Vietnam at about 12°N to the northeast. (3) The northern SCS is dominated mainly by a cyclonic circulation system. There is a cyclonic circulation system near and north of Section N2. In the next place, there is a not wide scope of the anticyclonic circulation southeast of Hainan Island. (4) The southeastern SCS is dominated mainly by the cyclonic circulation system, i.e., there are a wider scope of the cyclonic circulation west of Balawan Island and the cyclonic circulation southeast of a warm eddy W1. In the next place, there is a not wide scope of the anticyclonic circulation northwest of Borneo. (5) Comparing the results of circulation in SCS during summer of 2000 with those during summer of 1998, it is found that they agree qualitatively, but there is the some difference between them in quantity. This shows that the circulation in SCS has obviously seasonal feature. (6) Comparing the hydrographic structure and distribution of stream functions with the SSH data from TOPEX/ERS-2 analysis in SCS during August of 2000, they agree qualitatively.