热带大气季节内振荡的一个数值模拟研究

文中分析了中国科学院大气物理研究所全球气候谱模式ALGCM (R4 2L9) 12a(1978～ 1989年 )积分的逐日输出结果 ,并与 1978～ 1989年的逐日NCEP资料对照 ,以此对热带季节内振荡 (30～ 6 0d振荡 )进行数值模拟研究。分析表明 ,该模式在热带地区可以模拟出明显的季节内振荡 (ISO)的准周期信号 ,并抓住了热带ISO的基本传播特征 ,能较好地再现东、西半球传播速度的差异 ,同时模式模拟存在东传要好于西传 ,冬、春季的模拟要好于夏、秋季的现象。该模式模拟的热带ISO的强度较许多大气模式明显提高 ,尤其是对 2 0 0hPa上ISO动能强度的模拟。模式基本模拟出了ISO低层辐合、高层辐散的水平风场特征。模式较好地再现了热带ISO纬向风的垂直结构。此外 ,观测资料表明热带ISO在冬、春强 ,而夏、秋弱的季节性倾向与ISO的年际变化相联系 ,模拟的ISO在季节性倾向偏差上表现为冬、夏相对强 ,而春、秋相对弱。垂直速度、散度、水汽等物理量的配置同NCEP资料的结构特征仍有明显差异 ,模拟的ISO空间分布也不太理想 ,表明要很好模拟ISO结构和空间分布特征 ,还须做不少工作。

A GCM STUDY ON TROPICAL INTRASEASONAL OSCILLATION

The ability of a atmospheric general circulation model to simulate the tropical intraseasonal oscillation (ISO) (30-60 day) has been studied using the output of global spectral model (ALGCM (R42L9)) of the Institute of Atmospheric Physics, Chinese Academy of Sciences, compared with the results from the daily-mean reanalyzes data from NCEP/NCAR for the year 1978-1989. The model displays an evident periodic signal of intraseasonal oscillation in tropical area. The basic moving character of tropical ISO is prominent, and the change in phase speed between eastern and western hemispheres is also well present, the simulation of eastward propagating is better than that of the westward propagating, it is better reproduced in winter and in spring than in summer and in autumn. Although most models underestimate the strength of the ISO, this model has better ability to simulate the strength of the tropical intraseasonal oscillation, especially a marked strong kinetic energy of ISO at 200 hPa. This model basically simulates horizontal structure of the wind of ISO with convergence in lower air and divergence in upper air. The vertical structure of the zonal wind is also well reproduced. Moreover observed results show that the representing of seasonal preference to form strong ISO in winter and in spring is related to ISO's interannual variability, but it is represented in this model with strong ISO in winter and summer and weak ISO in spring and autumn. The structure of some physical elements such as vertical velocity, divergence and specific humidity and the special distribution of ISO have also differences with these from NCEP reanalyzes data, which make it clear to develop this model to simulate the structure and special distribution of ISO.