南黄海及东海北部夏季若干水文特征和环流的分析

AN ANALYSIS OF SUMMER HYDROGRAPHIC FEATURES AND CIRCULATION IN THE SOUTHERN YELLOW SEA AND THE NORTHERN EAST CHINA SEA

利用“中韩黄海水循环动力学合作研究”1 997年 7月航次和“黄海综合环境调查”1 998年 8月航次观测所得的CTD资料 ,对南黄海及东海北部夏季的水文特征和特大洪水年长江冲淡水扩展特征进行探讨。同时还根据夏季所施放的卫星跟踪漂流浮标的轨迹、底层人工水母的漂移路径及等密面深度的分布对夏季环流作了阐述 ,提出夏季南黄海环流并非单一的气旋式系统 ,其内部还存在着气旋、反气旋的多个较小的环流 ;东海北部交替出现气旋、反气旋涡旋。

Summer hydrographic features and the extension of the Changjiang River Diluted Water in the southern Yellow Sea and northern East China Sea are described, based on the CTD data measured in summer cruise (July 1997) of “PRC Korea Joint Investigation of Ocean Circulation Dynamics in the southern Yellow Sea” and that (August 1998) of “Comprehensive Hydrographic Investigation in Continental Shelf of the Yellow and the East China Seas”. Analyses show that there are several cold water areas induced by tidal mixing near shore in summer,which is one of the outstanding features in the Yellow Sea. The satellite infrared imagery on the July 28 of 1998 demonstrated the belt of cold water coincided completely with topography near the edge of Subei shallow shoal and it also shows radiated stripes with low temperature alternatively,which implies that the upwelling cold water near the Subei shallow shoal is totally caused by tidal mixing. Changjiang River Diluted Water is another surface important feature in summer. The Changjiang River runoff from the river mouth flowed southeastward firstly,and then turned to northeast at about 31°N,122°30′E toward the direction of Chejudao to form a distinct fresh water tongue which almost extended through to Chejudao in the high flooding year of 1998. According to the in situ CTD observed data from the August of 1998 and the analysis of historical data,the authors suggested that the extension of Changjiang River Diluted Water could be summarized into three stages after it flows into the sea,i.e. turning,extending and transmitting stages. \;In the meantime,the summer circulation is also depicted in this paper,based on the satellite drifter buoy trajectories deployed in summer,the bottom drifter trajectories in the July of 1997 and the distribution of depth at 23.0m isopycnal in the August of 1998. The results show that one part of coastal currents near the Subei shallow shoal flow southeastward along the 40\_50m isobath,and then turns by east flowing into the East China Sea at about 32°—33°N,whereas another part flows northward along 124°E at about 33°30′N. Thus,an anti clockwise cyclonic circulation is formed. In the east of the study sea area,there is a warm water tongue with relative high temperature stretching from the northeast to the southwest,which forms a clockwise anticyclonic circulation. The existence of both cyclonic and anticyclonic circulations make the water between 123°E and 124°E flow northward,up to the northern Yellow Sea. Meanwhile,three alternative gyres are present in the northern East China Sea:the cyclonic gyre out of the Changjiang River mouth,the cyclonic gyre between the sea area of 125°\_ 126°30′E ,30°—32°N, and the anticyclonic gyre between 123°30′—124°30′E,31°\_32°N.