珠江冲淡水季节变化及动力成因

Seasonal variation of the Pearl River diluted water and its dynamical cause

依据珠江口及其附近海域2006-2007年4个航次的CTD资料,分析珠江冲淡水的扩展形态和垂向结构,结果表明:表层冲淡水仅在夏季同时向粤西和粤东扩展,其余季节以西向扩展为主,而底层冲淡水全年向西扩展;冲淡水的主体部分大致位于10 m水深之上,但最大厚度在秋季可以超过20 m水深。通过结合同期风、海流、潮汐资料分析发现径流和风是控制冲淡水扩展范围和垂向结构的关键因子,夏季珠江冲淡水的范围最广,其次是春季,冬季最窄;夏季西南季风有利于其向东及向外海扩展,东北季风驱使珠江冲淡水向西扩展并制约冲淡水向外海扩散;粤西的水位梯度全年都驱动沿岸流向西流,而粤东的水位梯度仅在夏季有利于珠江冲淡水东向扩散,相应的粤东沿岸流在夏季指向东北,其余季节均指向西南。

The Pearl River diluted water （PRDW）plume shape and vertical structure were analyzed based on the CTD data observed in the Pearl River estuary and surrounding sea areas during 2006 to 2007. The results showed that the surface of PRDW expanded both westward and eastward in summer, and expanded mainly westward in other seasons,however,the bottom of PRDW expanded westward for the whole year. The main part of the PRDW located at upper 10 m,and the maximum thickness could exceed 20 m in autumn. According to the wind, current and tide data in the corresponding period, the key factors for PRDW plume range and vertical structure were analyzed, which were mainly affected by river discharge and wind. The plume size was largest in summer,medium in autumn, while it was smallest in winter. The southwest monsoon was conducive to the eastward and offshore expansion of PRDW, while the northeast monsoon drove PRDW to expand westward and constrained the offshore expansion. The sea level gradient along the west coast of Guangdong province drove the long shore current flow westward for the whole year, however, the sea level gradient along east coast was only favorable to eastward expansion of PRDW in summer, and the long shore current flowed northeastward in summer and southeast in other seasons.