东海沿岸海区垂直环流及其温盐结构动力过程研究 Ⅱ.温盐结构

DYNAMIC PROCESS OF VERTICAL CIRCULATION AND TEMPERATURE-SALINITY STRUCTURES IN COASTAL AREA OF EAST China SEA Ⅱ. THE STRUCTURE OF THE WATER TEMPERATURE AND SALINITY

对于本研究采用的动力学模型及其垂直环流的模拟结果已在第Ⅰ部分论述。作者将对与垂直环流对应的温、盐结构进行分析。温度和盐度模拟结果表明 :冬季东海沿岸海区的温、盐分布均为近岸低、外海高 ;近岸温、盐呈垂直均匀分布 ,在外海出现分层 ,其温度为表层高、底层低 ,而盐度却为表层和底层高 ,中层偏低 ,长江口以南的近表层以下形成自近岸伸向外海的弱低盐水舌 ;长江冲淡水区及长江口以北和其以南外海的近表层有温、盐跃层生成 ,深底层温、盐呈均匀分布 ,且保持低温高盐特征 ;随着海区自北往南纬度的降低 ,岸坡和水深的增大及沿岸下降流的增强 ,温度和盐度自近岸至外海的垂直均匀分布跨度逐渐变窄 ;外海近表层的温、盐跃层强度自北至长江口逐渐增强 ,而自长江口至南逐渐减弱 ,其位置自北往南逐渐上移 ;冬季沿岸下降流使长江冲淡水区的盐跃层变厚。夏季海区的温度分布为近岸和外海高 ,近岸稍远出现冷水涌升 ,垂向上呈现显著分层 ,盐度分布为近岸低、外海高 ;长江冲淡水区及杭州湾以南外海的次表层存在温、盐跃层 ,其跃层以上出现混合层 ,且保持高温低盐特征 ,跃层以下温、盐大致呈均匀分布 ,并保持低温高盐特征 ;随着海区自南往北纬度的增高、岸坡和水深的减小及沿岸上升流自南至长江口和自长江口至北?

In the last paper (Liu et al,2004), authors have discussed significance, contents and method on this study and the simulated results of the vertical circulation. In this paper, we analyze the simulated results of the water temperature and salinity. Numerical simulation results of the water temperature and salinity in the coastal area of the East China Sea demonstrated different distribution characteristics in wintertime and summertime. In wintertime, water temperature and salinity are low and uniform vertically in near shore, high and stratifies in the offside sea. In the offside sea, the water temperature is high in the surface layer, low in the bottom layer, and the salinity is high in the surface and bottom layers, low slightly in the mid-layer and gradually become high from the near shore to the offside sea. A slightly low salinity water tongue forms below the near surface layer of the southern area of the Changjiang mouth and spreads to the offside sea from the near shore. The stronger thermocline and halocline form in the Changjiang diluted water area and in the near surface layer of the offside sea of the northern and southern of the Changjiang mouth. The water temperature and salinity distributions are uniform in the bottom layer of the offside sea, characterized by low temperature and high salinity. With lowering of the latitude, increasing of the continental slope and the water depth and enhancing of the coastal downwelling from the north to the south, the vertical uniform distribution widths of the water temperature and salinity in the near shore become narrow gradually. The thermocline and halocline intensities of the Changjiang diluted water area strengthen gradually from the north to the Changjiang mouth, and weaken gradually from the Changjiang mouth to the south. The thermocline and halocline intensities in the near surface layer of the offside sea weaken gradually from the north to the Changjiang mouth, and strengthen gradually from the Changjiang mouth to the south and shift upwards gradually from the north to the south. The halocline of the Changjiang diluted water area thickens due to the effect of the coastal downwelling. In summertime, the water temperature is high in the near shore and the offside sea, low off the near shore and the cold waters rise. The water temperature change is great between the surface layer and the bottom layer compared with that of the wintertime, and the stratification is more evident in the vertical direction. The salinity is low in the near shore, high in the offside sea, and the salinity change is small in subsurface layer of the offside sea of the Changjiang mouth and its southern part. The thermocline and halocline form in the Changjiang diluted water area and the subsurface layer of the offside sea of the southern of the Hangzhou Bay. Mixing layer occurs above the thermocline and halocline and characterized by high temperature and low salinity, the temperature and salinity are uniform below the thermocline and halocline and characterized by low temperature and high salinity. With increasing of the latitude, decreasing of the continental slope and the water depth, enhancing-weakening of the coastal upwelling from the south to the north, the thermocline and halocline intensities of the Changjiang diluted water area strengthen gradually from the south to the Changjiang mouth and weaken gradually from the Changjiang mouth to the north, whereas the thermocline and halocline intensities of the subsurface layer of the offside sea weaken gradually from the south to the Changjiang mouth and strengthen gradually from the Changjiang mouth to the north. The thermocline and halocline of the offside sea shift upwards gradually from the south to the north. The halocline of the Changjiang diluted water area thins due to the effect of the coastal upwelling.