呂宋海峽渦旋之脫離與運動

Abstract

本研究利用POM(Princeton ocean model)建構一個高解析度的區域海流數值模式來模擬並描述南海(South China sea)的流況。南海模式的範圍東西向介於99度~124度E，南北向介於2度~27度N，水平解析度為1/16度x 1/16度，垂直方向有26個σ層。利用較大模式範圍輸出之結果，提供南海模式所需之初始及邊界條件，並指定AVHRR(Advanced very high resolution radiometer)的海表面溫度。本模式可重現南海季節、季內變化。渦旋脫離後向西行進的速率與此區域之第一斜壓羅士培波之行進速率(~ 0.1 m/s)相近，可推論此區之渦旋主要是搭乘第一斜壓羅士培波向西行進。由於黑潮入侵強度的冬夏差異，使得呂宋海峽附近之渦旋脫離週期於夏季較長為90~120天，冬季較短為40~50天，冬天形成之渦旋個數較多。

The present study used a higher resolution numerical model to simulate and describe the circulation of the South China Sea (SCS). The domain of SCS model is from 2 degree N to 27 degree N, and 99 degree E to 124 degree E. The horizontal grid size is 1/16 degree , and there are 26 sigma levels in the vertical. The SCS model derives its initial and open boundary conditions from a larger scale model and prescribes sea surface temperature from the AVHRR (Advanced Very High Resolution Radiometer). The SCS model is capable of reproducing the seasonal and intra-seasonal variations. The propagation speed of eddies is similar to that of the baroclinic Rossby waves (~ 0.1 m/s), suggesting that long Rossby waves have effects on eddies over the study region. The periods of eddy shedding estimated from Strouhal number are around 40 ~50 days in December and are about 90~120 days in August, respectively. The seasonal variability of the Kuroshio intrusion results in more eddies in winter than in summer.