FGOALS模式4个版本太平洋年代际气候变率模拟的比较

Comparison of Pacific Interdecadal Variability Simulated by Four Versions of the LASG/IAP Flexible Global Ocean–Atmosphere–Land System Model

本文选用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)发展的全球海洋—大气—陆面气候系统模式(FGOALS)的4个版本g2.0、s2.0、g1.1和g1,利用模式的长时间积分结果,结合观测、再分析资料比较、评估模式对太平洋年代际变率的模拟能力,并通过对海气相互作用及其海洋动力过程分析,探讨了模式中太平洋年代际振荡形成机制。研究发现,FGOALS模式g2.0和s2.0版本对太平洋年代际振荡(PDO/IPO)的模拟能力优于g1.1和g1。模式中太平洋年代际变率的正反馈过程与Bjerknes(1969)提出的海气相互作用正反馈机制有关,其负反馈则主要与海洋内部动力过程有关。太平洋异常经向热量输送将热带与中纬度海洋联系在一起,可以抑制正反馈作用,但无法使得年代际振荡变化位相发生反转;FGOALS模式中,热带海表温度(SST)暖距平信号通过大气桥影响热带外大气环流,在海气作用下,热带与热带外海洋次表层分别以Kelvin波和Rossby波的形式传播,使得冷暖位相反转,4个版本均能再现这种负反馈机制。但不同版本Rossby波所处的纬度不同,太平洋SST异常年代际变化信号最明显的范围越宽,则由此激发的Rossby波便更为偏北,纬度越高Rossby波西传的时间也越长,PDO/IPO的周期与其SST异常的经向尺度密切相关。

The long-term control simulation（20th century experiment） of four versions of the coupled atmosphere–ocean global climate model FGOALS（Flexible Global Ocean–Atmosphere–Land System Model）, g2.0, s2.0, g1.1 and g1, developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics（LASG）, Institute of Atmospheric Physics（IAP）, Chinese Academy of Sciences, combined with observational and reanalysis data, are analyzed and compared. In terms of evaluating how realistic the model is in simulating the climatology, the physical mechanisms of Pacific decadal variations are discussed. It is found that g2.0 and s2.0 simulate more reasonable interdecadal Pacific variations than g1.1 and g1. The results indicate that the positive air–sea interaction feedback should be related with the Bjerknes positive feedback mechanism. The negative feedback is mainly associated with the ocean dynamic process. The anomalous meridional heat transport in the Pacific links the tropical and extratropical regions, which inhibits the positive feedback effect. The tropical SST（Sea Surface Temperature） warm anomaly signal, via the atmospheric bridge, affects the extratropical atmospheric circulation. With the air–sea interaction, Kelvin waves and Rossby waves spread across the tropical and extratropical subsurface ocean, respectively. Such negative feedback behavior can be reproduced by the four versions of FGOALS. The study quantifies some of the factors responsible for the periods of Pacific interdecadal variations. The farther from the equator the maximum zonal SST is, the wider the decadal variations are. Subsequently, poleward heat transport requires a longer time, the surface wind stress curl anomalies will extend farther north, and ocean Rossby waves appear much more northward with longer transport periods.