加利福尼亚流系流场的季节性演变

本文利用三维数值模型(ROMS-Co Si NE)分析了整个加利福尼亚流系水平流场的季节性演变过程,研究了美国加州中部海域流场垂直结构的季节性变化特征,并探讨了其动力学机制。研究发现:(1)数值模型能够较为准确的模拟流场的季节性变化,与浮标观测数据以及前人的研究结果符合良好;(2)从表层到200m,加利福尼亚潜流向高纬度扩张,近岸上升流急流则向高纬度撤退,加州南部海域的中尺度涡更显著;(3)在加州中部海域,近岸急流的最大值(约15cm/s)发生在夏季,位于近岸的表层海域;加利福尼亚潜流最大值(约4cm/s)发生于冬季,出现在离岸100km的125m处;加利福尼亚流在春季达到全年最大值(约5cm/s),流轴位于离岸(400—600km)的表层海水。加利福尼亚流系的流场具有显著的季节性变化,研究进一步表明这主要受地转关系调控。

SEASONAL EVOLUTION OF CURRENTS IN THE CALIFORNIA CURRENT SYSTEM

A three-dimensional model (ROMS-CoSiNE) was used to study the seasonal evolution of currents in the California Current System (CCS), especially the alongshore currents in the central CCS, and further to investigate the underlying dynamics. It was found that the model could simulate well the seasonal evolution of currents in CCS, with results close to mooring data and previous studies. From surface to 200m, Southern California eddy became stronger, and California Undercurrent extended poleward while coastal upwelling jet retrieved. In the central CCS, coastal upwelling jet reached a mean maximum velocity of about 15cm/s at surface near coast in summer, California Undercurrent obtained a maximum velocity of about 4cm/s at 125 m in distance of 100 km off coast in winter, and California Current reached a maximum velocity of about 5cm/s with the core in the offshore (400-600km) surface waters in spring. Thus, CCS currents had significant seasonal cycle, which was mainly modulated by geostrophic balance.