大气环流模式和耦合模式模拟的降水-海温关系之比较

Relationship between Rainfall and Sea Surface Temperature Simulated by LASG/IAP AGCM and CGCM

本文讨论了气候系统耦合模式FGOALS_s模拟的局地降水和海温的关系,并通过与单独大气模式SAMIL的AMIP试验结果进行对比分析,考察了海气耦合过程对局地降水和海温关系模拟的影响。结果表明,耦合模式FGOALS_s和单独大气模式SAMIL在模拟局地降水和海温关系上各有优势。在赤道中东太平洋地区,观测中局地降水和海温的关系是海洋强迫为主,FGOALS_s模拟的海洋对大气的强迫比观测偏弱,因此,SAMIL相对于FGOALS_s更有优势。在西北太平洋东部地区,观测中夏秋季节降水和海温的关系是大气强迫为主,由于考虑了海气相互作用过程,FGOALS_s对降水和海温关系的模拟能力要优于单独的大气模式。此外,由于大气模式SAMIL的云参数化方案导致的模拟偏差,在赤道中东太平洋地区（9～11月）,降水增加时入射的短波辐射通量也是增加的,并且这种模拟的偏差在耦合后仍然保留了下来,导致了与观测不符的云-辐射反馈过程。因此,改进大气模式的云参数化方案是未来工作重点之一。此外,分析发现耦合模式模拟的潜热通量的变化过分依赖海气湿度差。

This paper evaluates the relationship between rainfall and sea surface temperature （thereafter SST） simulated by the new version of LASG/IAP （State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences） climate system model （FGOALS_s）, which takes the recently improved version of spectral AGCM （SAMIL） as its atmospheric component. To understand the impacts of air-sea coupling on the simulation of relationship between rainfall and SST, re-sults from FGOALS_s and AMIP-type simulations with SAMIL are compared. Since observational results show thatrainfall anomalies are mainly forced by SST in the eastern equatorial Pacific and oceanic forcing from FGOALS_s is weaker than that from the observation, SAMIL has a better performance in simulating the relationship between rainfall and SST in the eastern equatorial Pacific. On the other hand, in summer and autumn, the SST anomalies in the western North Pacific are mainly induced by atmospheric forcing, so coupled model FGOALS_s can properly capture the nature of relationship between rainfall and SST because the air-sea coupling processes are included. Bias related to convection parameterization used in SAMIL leads to an increased surface downward shortwave radiation flux while rainfall increases in the eastern equatorial Pacific during September to November. To some extent, this discrepancy maintains after coupling. So it is urgent to improve the convection parameterization in the AGCM. Besides, it is found that the latent heat flux overly depends on the air-sea moisture differences in the coupled model.