气候系统模式FGOALS-s1.1对热带降水年循环模态的模拟

文中评估了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG/IAP)新一代耦合气候模式Fgoals_s1.1对热带降水年循环模态的模拟能力。通过与观测表层海温(SST)强迫的大气模式SAMIL试验结果比较,分析了海气耦合过程对年循环模态模拟效果的影响。结果表明Fgoals_s1.1能合理再现热带地区降水年循环模态的基本特征。Fgoals_s1.1模拟出了年平均降水场中的主要降水中心,但模拟的赤道和南太平洋降水偏多,而北太平洋降水则偏少。Fgoals_s1.1的季风模态降水呈现与观测一致的关于赤道反对称的特征,其模拟偏差大部分来自大气分量,尤其是在赤道外。Fgoals_s1.1的主要缺陷在于它对春秋非对称模态模拟能力低于单独大气模式,这主要是由于耦合模式模拟的SST距平的年循环位相与观测相反。SST纬向梯度的位相偏差使得太平洋沃克环流和印度洋的反沃克环流在春季强于秋季,最终导致模拟的春秋非对称模态的偏差。Fgoals_s1.1模拟的季风区范围接近观测,存在的问题在于模拟的西北太平洋季风区、东亚季风区都偏小。本文结果表明,大气模式偏差仅是Fgoals_s1.1在降水年循环模态模拟上的偏差的部分来源,改进模式模拟的SST,特别是赤道地区SST季节循环,是今后Fgoals_s1.1发展过程中急需解决的问题。

The annual modes of tropical precipitation simulated by LASG/IAP ocean atmosphere coupled model Fgoals-s1.1.

This paper evaluates the performance of LASG/IAP ocean-atmosphere coupled model Fgoals-s1.1 on simulating the annual modes of tropical precipitation.To understand the impacts of air-sea coupling on the annual modes,the result of an off-line simulation of the atmospheric component of Fgoals-s1.1,e.g.LASG/IAP atmospheric general circulation model SAMIL,is also analyzed.It is shown that Fgoals-s1.1 can reasonably reproduce major characteristics of the annual modes of tropical precipitation.The simulated annul mean rainfall matches well with the observation in maximum centers.Nonetheless,the coupled model also shows clear biases,e.g.the overestimation of rainfall amount over the equatorial Pacific and tropical South Pacific,the underestimation of rainfall over the northern equatorial Pacific.The monsoon mode simulated by Fgoals-s1.1 shows an equatorial anti-symmetric structure,which is close to the observation.The bias of the coupled model in simulating the global monsoon resembles that of SAMIL,especially over the subtropics.The main deficiency of Fgoals-s1.1 is its failure in simulating the spring-fall asymmetric mode.This is attributed to a false phase of the SST annual cycle over the equatorial central-eastern Pacific and Indian Ocean,which has led to a serious bias of the Walker circulation over the equatorial Pacific and the anti-Walker circulation over the Indian Ocean in spring and autumn.In addition,the western North Pacific monsoon simulated by the coupled model occupies a smaller territory than reality,and this is also the case for the Indian monsoon.Our study suggests that the bias of a fully coupled ocean-atmosphere model can be partly attributed to the bias in its atmospheric component.The performance of Fgoals-s1.1 in simulating the annual cycle of equatorial SST needs to be further improved.