南海混合层年循环特征

摘要

Based on Levitus 94’ climatological temperature and salinity data, the temporal and spatial features of the mixed layer in the South China Sea (SCS) are derived, and the regular pattern of the mixed layer depth and temperature are analysed. Data analysis indicates that the monsoon has an obvious impact on the temporal and spatial features of the mixed layer in the SCS through the adjustment of the current field. The complicated effect of the wind includes not only influence on the mixed layer depth directly through sea surface Ekman process, but also divergence or convergence forced by the large-scale circulation, which would favorite or suspend development of the mixed layer depth. The relationship between the mixed layer depth and temperature over the SCS is revealed. The formation of the maximum mixed layer depth in summer exhibits a process that the 28℃ isotherm line overlaps the bottom of the mixed layer, whereas the formation of the maximum mixed layer depth in winter is a process that the 28℃ warm water completely disappears and the isotherm lines intersect to the bottom of the mixed layer, and the seasonal thermocline is ventilated in the northern SCS.%通过分析Levitus 1994版气候平均温盐资料，得到南海混合层的时空分布特征，剖析了混合层深度及其内部温度的季节变化规律。资料分析表明：季风通过流场调整对南海混合层的时空分布有着明显的影响。这种影响的复杂性在于它不但通过海洋表层Ekman效应来影响混合层深度，而且还通过大尺度环流造成的辐散或辐合来限制或促进混合层深度的发展。研究发现混合层深度与混合层内温度存在着如下关系：夏季最大混合层的形成是28°C等温线与混合层底达到相互贴合的过程；冬季最大混合层的形成是28°C水体完全消失并且等温度线与混合层底达到相交最多、相交最为垂直的过程，这时对应着冬季南海北部温跃层的通风；大于或等于28°C的水体总是位于混合层以内。