1988年反厄尼诺(La Niña)事件的数值模拟

用中国科学院大气物理研究所高分辨率、自由表面热带海洋环流模式对厄尼诺/南方涛动(El/Southern Oscillation)循环中另一重要位相La Niña事件进行了数值模拟研究。模式区域为南北纬30°之间的热带太平洋,经纬圈水平方向分辨率分别为2°和1°,垂直方向分为不等距的14层;模式中考虑了盐度并引入与洋流切变和层结稳定度有关的垂直扩散参数化方案。在观测到的海表风应力、热量和淡水通量(蒸发与降水之差)驱动下,所发展的模式从1984年积分到1989年。本文给出模式对近十几年来最强的1988年La Niña事件进行数值模拟的结果,着重分析La Niña期间热带太平洋海面起伏、流场和温度场时空演变,以及La Niña和El期间变量场时空结构差别。文中还进行了模式结果和一些观测资料间的比较。

SIMULATION OF THE 1988 LA NIÑA EVENT WITH A FREE SURFACE TROPICAL PACIFIC OCEAN GCM

A free surface tropical Pacific ocean GCM with high resolution developed at the Institute of Atmospheric Physics is used to simulate the La Niña event, one of the important phase in the El Ninño/Southern Oscillation (ENSO) cycle. The model covers the tropical Pacific Ocean between 30°N and 30°S with horizontal grid spacing of 1° in latitude and 2° in longitude. There are 14 vertical layers with eight layers in the top 200 m. The model includes the salinity and adopts the Richardson number dependent vertical mixing parameterization related with currents shear and stratification stability. Observed atmospheric forcing fields, sea surface wind stress, heat flux and water flux (evaporation minus precipitation),force the model over the periods of 1984-1989. Numerical simulation of the 1988 La Niña event is presented in the paper with emphasis on describing the time and space evolution of sea level, currents and temperature, and on contrasting the differences between the La Niña event and the El Ninño episodes. Also. some comparisons between the model results and corresponding observations are given.