一个斜压海洋风生环流的数值模拟

NUMERICAL SIMULATION STUDY OF WIND-DRIVEN BAROCLINIC OCEAN CIRCULATION

中文摘要:

      为研究大尺度海气相互作用、气候以及气候的变化,一个具有规则海岸线和无海底地形的三层斜压海洋模式已经建立起来。积分区域包括了赤道地区在内,南北方向从-2750 km到+4750 km,东西方向宽10000 km,总深度是4 km。模式方程为原始方程,用了静力近似和Bou-sinesq近似。模式数值积分分两个阶段,在第一个阶段,海洋环流从静止状态开始,以只随纬度变化的年平均风应力和海表热通量作为强迫边条件数值积分十年,这时海洋上层的环流和温度都趋于平稳,我们将第十年末的积分状态作为模式气候的准平衡态。计算结果模拟了热带太平洋上气候平均的温度分布以及主要海流的大尺度特征,如赤道地区的狭长冷水带和强上翻区、南赤道洋流、北赤道逆流以及表层下面沿赤道自西向东的潜流。在第二个阶段,以在第一个阶段末尾得到的准平衡态作为初值,分别用冬季和夏季的风应力作为强迫边条件再积分一年。比较这两种计算结果,我们看到海洋环流随信风系统的季节变化也呈现出明显的季节变化,特别是北赤道逆流,其强度在夏季强,在冬季弱甚至不出现。南赤道洋流无论哪个季节都穿过赤道,在赤道以北的南赤道洋流冬季比夏季强,而在赤道以南的南赤道洋流夏季比冬季强。

英文摘要:

      A three-level baroclinic ocean model has been developed for studing large air-sea interaction, climate and climatic change. The formulation of the model is based on the primitive equations with the hydrostatic and Bousinesq approximations. The numerical integration is done in two phases. In the first phase, the model was integrated starting from an rest state over ten years under the annual mean wind stress. At the end of the first phase, a quasi-equilibrium state in the upper levels was reached. The simulated results show that the major large scale feature of annual mean temperature field and main currents in the tropic Pacific Ocean, such as the narrow belt of cold water and strong upwelling in the equatorial region, the South Equatorial Current, North Equatorial Countercurrent and Undercurrent, have been reproduced. Then by using the results at the end of the first phase as an initial condition, and using She wind stress in winter and in summer as upper boundary conditions, we carried out an integration for one year. It is shown that the seasonal variations of the ocean currents are apparently relatad to the seasonal variation of trade wind system. Simulated Equatorial Countercurrent is strong in summer and weak or disappeared in winter. The South Equatorial Current which located in the north of the equator is stronger in winter than it is in summer, but the one in the Southern Hemisphere is strong in summer and weak in winter.