摘要:本文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）研发的全球气候系统模式（FGOALS）的4个版本（FGOALS-g2、s2、g3、f3-L）对赤道太平洋地区的海温、降水气候态和季节循环的模拟能力。本文从海气耦合机制和热量收支的角度对耦合模式结果和相应的大气模式比较计划试验（AMIP）进行了对比分析，探讨了造成这一地区海温和降水模拟偏差的原因。结果显示，上一代模式g2和s2的海表温度均方根误差大于2°C，新一代模式g3和f3-L模拟的均方根误差降低50%，为1°C左右。因为新版本中赤道太平洋地区的净短波辐射平均态误差的减小，海洋上层热量动力输送过程的改善和净短波辐射与海温回归关系改进，赤道太平洋地区海温的平均态，南北温度和降水的不对称性都更加接近观测。f3-L比g3在上述方面改进更多，海温也更加合理。但是新一代版本模拟的降水均没有显著改进，赤道北侧ITCZ的降水偏大4 mm d?1。对流降水带来的凝结潜热释放加强了南北非绝热加热梯度，越赤道南风偏差抵消了一部分因为短波辐射偏大带来的海温偏暖，这说明海温平均态的改善是模拟误差相互抵消的结果。在季节循环的模拟方面也存在类似的现象，f3-L和g3中的海温年循环有所改进但较观测振幅仍旧偏弱。这是因为f3-L和g3模拟的经向风和潜热的年循环振幅比前版本要偏强，误差加大的同时也更大地抵消短波辐射的年循环偏差。g2和s2模拟的海温在赤道东太平洋则存在一个虚假半年循环分量，这主要是由潜热通量半年循环偏差所引起的。
关键词:海气相互作用/
模式评估/
季节循环/
气候系统模式
Abstract:This study evaluated the ability of four versions of flexible global ocean–atmosphere–land system model (FGOALS-g2, FGOALS-s2, FGOALS-g3, FGOALS-f3-L) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP), Chinese Academy of Sciences in simulating the climatology and seasonal cycle of the tropical Pacific precipitation and sea surface temperature (SST). This paper compared coupled and atmospheric model intercomparison project (AMIP) simulations in terms of atmosphere-ocean feedback mechanisms and heat budget analysis to investigate the formation of precipitation and SST biases. Results exhibited notable improvements in FGOALS-g3 and FGOALS-f3-L compared with previous versions, such as a reduction of 50% of root-mean-square error (RMSE)of SST, decreasing from above 2°C in FGOALS-g2 and FGOALS-s2 to 1°C in FGOALS-f3-L. However, there are negligible improvements in precipitation. FGOALS-f3-L reproduces the climatology mean of SST, the meridional asymmetry of SST, and the precipitation in the East Pacific well because of the reduction of errors in the mean state of shortwave radiation and its reasonable representations of ocean dynamic heat transport and surface shortwave radiation feedback; hence, FGOALS-f3-L shows better improvement in the aforementioned sectors than FGOALS-g3. Furthermore, excessive rainfall biases in the northern side of the equator become more severe than those of the previous models, which is greater than 4 mm d?1. These overestimated convections bring latent heat, which enhances the latitudinal diabatic heat gradient and strengthens the cross-equatorial south wind. Errors in the seasonal cycle of wind actually cancel out part of the warm biases of SST, resulting from the overestimation of shortwave radiation. Similar error sources existed in the simulated seasonal cycle, characterized by an improved annual cycle but a weaker overall amplitude in FGOALS-g3 and FGOALS-f3-L. Improved annual signal of SST results from the stronger amplitude of the annual cycle of the meridional wind and latent heat flux. Generally, errors in the seasonal cycle of wind and latent heat are bigger but cancel out the annual biases in the shortwave radiation flux. Therefore, the annual signal in SST seems to be enhanced than that of former versions. Meanwhile, the false semi-annual cycle of SST in FGOALS-g2 and FGOALS-s2 mostly results from the semi-annual cycle of the latent heat flux.
Key words:Air–sea interaction/
Model assessment/
Seasonal cycle/
Climate system model
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