南海上层海洋热结构的年循环与半年循环

Annual and Semi-Annual Cycles of the Upper Thermal Structure in the South China Sea

根据南海季风试验 (SCSMEX)期间南海内区的三个ATLAS (AutonomousTempera tureLineAcquisitionSystem)锚碇浮标资料 ( 1 998年 4月～ 1 999年 4月 ) ,采用谐波分析方法对南海上层海洋水温年循环、半年循环加以分离 ,发现无论在年循环还是在半年循环尺度上 ,1 8°N附近SCS1站与 1 3°N附近SCS3站的水温变化次表层与表层呈反位相 ;1 5°2 0′N附近SCS2站水温变化基本上次表层与表层同位相。这说明不同区域上层海洋热变化受不同的正压与斜压模态控制。其次 ,SCS2、SCS3两点水温年循环振幅均在次表层达到极值 ;而SCS1在表层达到极大值 ,在 1 0 0m深度达到次极大值。 3个站位水温半年循环振幅极值均出现在次表层内 ,这说明该层内的水温半年循环在温度变化趋势中所占的权重比在表层的权重大。

Based on three ATLAS Mooring buoy data provided by the SCSMEX project (South China Sea Monsoon Experiment), harmonic analysis method was applied to determine amplitudes and phases for the annual and semi-annual cycles of temperatures in the upper layer (1～250 m) in the South China Sea (SCS). At the stations of SCS1 (18°05′54″N, 115°35′48″E) and SCS3 (12°58′30″N, 114°24′30″E), temperature variances of annual and semi-annual cycle in the surface layer (surface to 50 m) are out-of-phase with those in the sub-surface layer (50 m through 250 m). However, corresponding temperature variations at the stations of SCS2 (15°20′36″N, 114°57′18″E) are vertiaclly in phase. Further studies suggest that temperature variations at SCS2 are controlled by the advection term, while temperature variations at the other two sites are dominated by the convection term induced by Ekman pumping. As far as the annual cycle concerned, maximum amplitude appears in the sub-surface at SCS2 and SCS3, but in the surface at SCS1. The maximum amplitude for the semi-annual cycle appears in the sub-surface similarly at the three sites. Nevertheless, the amplitudes for tha annual cycle at SCS1 and SCS3 decrease with depth beneath the mixed layer, which results in contribution of the semi-annual cycle compareable that of annual cycle, especially at SCS3.