南海海平面季节变化机制的研究

Study on the Mechanism of Seasonal Sea Level Variability in the South China Sea

利用Ssalto/Duacs卫星高度计的融合数据和英国气象局哈德利中心的EN4.2.1版本的数据产品,结合1.5层约化重力模式,研究了南海海平面季节变化规律及其影响机制。南海海平面季节变化特征显著,在冬季和夏季、春季和秋季呈现出相反的变化特征。南海区域平均海平面最高值出现在11月,最低值出现在6月,海平面变化年振幅约为10 cm。海平面季节变化信号能够解释南海西北和西南大陆架海域月平均海平面变化的70%~95%,而对南海内区及东部海域的解释方差较小,为20%~60%。南海海平面季节变化主要受比容效应和风应力强迫的动力海平面变化的影响,比容效应是南海东北部海域海平面变化的主要原因,能解释海平面季节变化的50%以上;风应力强迫只对南海中部海域的海平面季节变化起主导作用,其解释方差为50%~80%。导致南海中部海域海平面变化的风应力强迫包括热带太平洋风强迫和南海局地风强迫两部分。

Based on the temperature and salinity from the Ssalto/Duacs altimetry data and the Hadely EN4.2.1 data,seasonal sea level variability and its underlying mechanism in the South China Sea are studied with the 1.5-layer reduced gravity model.The results show that seasonal sea level variability is significant and exhibits opposite spatial variation in winter and summer,spring and autumn.The highest sea level appears in November and the lowest value appears in June,the magnitude of sea level variability is about 10 cm.Seasonal variability signal can explain 70%−95% of the monthly mean sea level variance in northwestern and southwest shelves of the South China Sea,but can only explain about 20%−60% of variance in internal and eastern areas of the South China Sea.Steric effect is important to sea level variability in northeastern South China Sea,and can explaine about 50% of the seasonal variability,while wind stress forcing plays a leading role in central South China Sea,and explains about 50%−80% of the variance.The wind stress forcing that results in sea level change in central South China Sea comes from the remote forcing from Tropical Pacific and the local forcing in the South China Sea.