长江口邻近海域水团特征与影响范围的季节变化

Ssonal variation of water mass characteristic and influence area in the Yangtze Estuary and its adjacent waters

基于2009年—2011年调查资料,研究长江口及其邻近海域水体温度和盐度时空分布特征,剖析该海域水团特征与影响范围的季节变化。结果表明,从春末到秋初,长江水以高温形式向外海扩展,秋末至翌年春初,径流水以低温形式从河口流向东南。西北部海区受黄海冷水团影响,水温较低,东北部受南黄海西部逆时针环流影响,盐度较低,东南部海区受黑潮及分支台湾暖流影响,呈高温高盐状态。受径流量和季风季节差异,长江冲淡水影响一般夏季最强,扩展范围最大,秋末冬初最弱。其双向延伸趋势在夏季有最清晰表现,一支自河口向东北方向延伸,指向南黄海中部,一支穿过杭州湾口及舟山群岛一带沿岸南下,或自长江口向东南方向扩展。温度垂向变化表明夏季存在上升流,并明确处于以31.5°N,122.67°E为中心,在经纬方向上各达1°范围内。

The spatial distribution and seasonal variation of temperature and salinity in Yangtze Estuary and its ad- jacent waters were examined during 2009-2011. Results show that from late spring to early autumn, high-temperature water extended from the estuary to the open sea. However, from late autumn to early spring, low-temperature water from adjacent rivers poured into the open sea from the estuary. Low temperature water in the northwest was influenced by the Yellow Sea Cold Water and low salinity water in the northeast was influenced by the counterclockwise circula- tion in the western part of the southern Yellow Sea. High temperature and salinity water found in the southeast was influenced by the Kuroshio Current and Taiwan Warm Current. With the effect of seasonal runoff and monsoon, the influence of Yangtze diluted water was usually strongest in summer and weakest when autumn changes to winter. Low salinity in summer clearly reflected the two-way extension trend of Yangtze diluted water. One was from the river mouth toward north or northeast to the southwest of Southern Yellow Sea, the other toward south or southeast to East China Sea. The depth profile of temperature predicted the presence of upwelling and estimated the centre （31.5°N, 122.67°E） and the scope （area of 1° in the direction of longitude and latitude）.