大气季节内振荡的耦合模式数值模拟

分析GOALS/LASG海气耦合模式10年积分200hPa纬向风场的逐日输出结果,引用1980～1989年期间逐日的NCEP/NCAR再分析资料作为实测对照,结果显示该耦合模式抓住了热带大气低频振荡(IO)的基本时空分布特征,模拟IO的强度较多数大气模式强而接近真实,但空间一致性仍不清晰,典型周期不够显著。NCEP资料与耦合模式都反映模拟IO的季节变化与其年际变化有关,模拟较强IO的年份表现IO的季节变化特征也较真实。模拟IO的年际变化与热带东太平洋的SST呈明显的负相关变化。SST暖异常的年份,IO活动较弱。IO变化滞后于SST异常60天左右的相关性最显著。对比单独积分GOALS/LASG的大气模式的结果,发现二者的主要差别在于耦合模式再现IO的季节性特征更真实,反映了海气耦合对IO变化的调制作用。利用海气耦合模式,理解IO对流活动与上层海洋的相互作用过程,是真实描述IO必要的手段。

Intraseasonal Oscillation in a Coupled General Circulation Model

Daily-mean reanalyses from the National Centers for Environmental Prediction/Na tional Center for Atmospheric Research (NCEP/NCAR) for the years 1980-1989 are used as verification data in a study of intraseasonal oscillation (IO) in the GOALS/LASG coupled general circulation model. The projection of the IO onto the upper troposphere zonal wind provides a useful measure of intraseasonal activities. The results show that GOALS/LASG captures the salient features of IO in the tropics. The simulated IO is more realistic than that by some other atmospheric general circulation models with respect to an increased intensity, while it is not as spatially coherent and not as typically periodical as the observed. There is a tendency in both NCEP and the simulation that the representing of seasonal preference for the IO to form during the boreal winter/spring is related to its interannual variability, with the correct seasonal signature being simulated during the year of stronger IO. It is suggested that the simulated interannual variability of IO is related to the sea surface temperature (SST) anomalies for the Nino 3 region of the central and East Pacific. In the year with positive SST anomalies, IO activity is weak. The most significant correlation appears 60 days behind the phase of IO. In comparison with the data from the atmospheric circulation model of GOALS/LASG with a specified annual cycle SSTs, the coupled model represents an increased seasonal signature, which suggests the regulation to IO by the ocean-atmosphere interaction. An accurate representation of IO can only be available by the using of coupled model.