南海大尺度动力场年循环和年际变化

ANNUAL AND INTERANNUAL VARIATIONS OF LARGE-SCALE DYNAMIC FIELD IN SOUTH CHINA SEA

应用COADS风应力、Levitus温度资料 ,描述了南海上层海洋动力场的年循环及其与热力场之间的关系和南海大尺度动力场的年际变化。针对冬、夏 2个季节 ,分析Sverdrup环流场与上层海温之间的关系。研究发现 ,上层海温变化与上层海洋环流基本结构非常相似 ,即上层海温变化在一定程度上反映了南海Sverdrup平衡 ,而且随着深度的增加 ,平均海温场与流函数场之间的对应关系更好。本文还着重分析了ElNi^no期间和LaNi^na期间的南海异常流函数场。研究发现 ,异常流函数场在ElNi^no期间的夏季主要是强化南海自身的环流结构 ,即强化南部反气旋式涡流 ( gyre)和强化北部气旋式涡流 ;冬季则削弱整个南海的气旋式流场。LaNi^na期间对夏季环流态的影响主要集中在南海北部 ,即削弱北部气旋式涡流 ,而对于南海南部的影响甚微 ;

Using wind stress data from COADS and temperature data from Levitus, analyses are made to describe the relationship between the upper layer dynamic fields and the temperature fields, and interannual variations in the large scale dynamic fields of the South China Sea(SCS). The pattern of Sverdrup circulation in summer and winter and its relationship with the upper sea temperature are expounded. It is found that the sea temperature spatial variation is very similar to the circulation structure in the upper ocean, which suggests that the sea temperature variation involves the Sverdrup balance. With increase of depth within the seasonal thermocline, the relationship between the mean sea temperature and the stream function fields exhibits an even better similarity than the surface case. Another emphasis is put on the anomalous Sverdrup stream function of the SCS during El Nio and La Nia events. It is found that the summer circulation in the El Nio year is stronger than in the normal years, which strengthens the anti cyclonic gyre in the southern SCS and the cyclonic gyre in the northern SCS. However, the impact of El Nio makes the circulation in winter weaker than in normal years though the southern and the northern cyclonic gyres combine into a basin wide cyclonic gyre. During the period of La Nia, the most obvious variation of summer circulation occurs in the central SCS, the northern gyre is generally weakened and the southern gyre is modified slightly. The winter circulation during La Nia is strengthened in the entire SCS.