南海上层水温的准双周(10—20d)变化

QUASI-TWO-WEEK (10—20 DAY) SEA TEMPERATURE VARIABILITY IN UPPER SOUTH CHINA SEA

对南海季风实验(SCSMEX)期间布设于南海中部的3个ATLAS海洋锚定浮标所观测的水温资料进行分析,结果表明:南海上层水温存在准双周(10—20d)变化,且主要发生在次表层,尤其在冬半年,温跃层的年循环对其有调制作用;次表层水温的振幅北部大于南部;南海上层的准双周振荡可分为3个垂向模态,即上下同位相、反位相、次表层先于表层;低层大气准双周振荡的强迫,是造成这种变化的主要原因,海面风应力强迫使得温跃层发生垂直位移,从而引起次表层水温的变化;表层水温(SST)的变化小于次表层,海面热收支是引起表层水温变化的主要原因,但次表层水温可以影响表层。

Based on the analysis of the sea temperature data which were observed from the three ATLAS mooring buoys deployed in the central South China Sea (SCS) during SCSMEX, the quasi-two-week (10—20 day) sea temperature variability in the upper SCS is found and primarily located in the subsurface layer especially in autumn and winter. In addition, it is modulated by the annual cycle of the thermocline. The amplitude of the quasi-two-week variability of subsurface temperature in the north SCS is larger than that in the south SCS. The quasi-two-week variability of upper-ocean sea temperature in the SCS can be classified into three modes by vertical configuration, that is, the temperature variability of subsurface is in phase to, out of phase to, and is ahead of that of surface. The main reason of this variability is low-level atmospheric forcing with the same oscillation period. The vertical displacement of thermocline that is driven by wind stress forcing results in subsurface temperature variability. Net surface heat flux is the main reason of the sea surface temperature variability whose amplitude is smaller than that of subsurface temperature variability. Sea surface temperature can also be affected by subsurface layer.