The Improvements of the Upper Zonal Currents by SST Assimilation Over the Tropical Pacific in a Coupled Climate Model
The Improvements of the Upper Zonal Currents by SST Assimilation Over the Tropical Pacific in a Coupled Climate Model
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DOI：
10.3389/feart.2022.828253
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Zhikuo Sun;Xin Gao;Jiangbo Jin;Juanxiong He;Fei Zheng;He Zhang;Xiao Dong;Qingcun Zeng
中科院分区：
文献类型：
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作者：
Zhikuo Sun;Xin Gao;Jiangbo Jin;Juanxiong He;Fei Zheng;He Zhang;Xiao Dong;Qingcun Zeng
热带太平洋的纬向上层海洋环流在调节热带太平洋的天气和气候方面起着至关重要的作用。然而，在最先进的气候模型中，它们的模拟效果很差。为了更好地重现热带海洋高层纬向流，我们采用了一种简单的偏置校正方案，即只将观测到的海表温度（SST）数据同化到一个耦合的地球系统模式中，该模式被称为中国科学院地球系统模式2 （CAS-ESM 2.0）。采用海温同化方法主要有两个原因：1)海温对热带地区海气相互作用的影响占主导地位；2)目前缺乏有效的、长期的海流观测资料。结果表明，海温同化可以通过减小海气湍流通量的偏置，显著增强太平洋赤道暗流（EUC）、北赤道逆流（NECC）和南赤道流（SEC）的强度。然而，海温同化对改善热带太平洋纬向流空间结构的模拟效果有限。热带太平洋地区风应力旋度的改善主要有助于太平洋EUC、NECC和SEC模拟强度的增强，也与海温偏压减弱引起的大气对流降水和海平面压力偏减小有关。
The upper zonal oceanic circulations in the tropical Pacific play a crucial role in modulating weather and climate in the tropical Pacific Ocean. However, they are poorly simulated in state-of-the-art climate models. We apply a simple bias correction scheme by only assimilating observed sea surface temperature (SST) data into a coupled earth system model, named the Chinese Academy of Sciences Earth System Model version 2 (CAS-ESM 2.0), to better reproduce the upper zonal currents in tropical oceans. There are mainly two reasons for this usage of SST assimilating method: 1) SST has dominant effects on the air–sea interactions over the tropical region; 2) The lack of effective and long-term ocean-current observation data currently. Our results show that the SST assimilation can significantly improve the strength of the Pacific Equatorial Undercurrent (EUC), the North Equatorial Countercurrent (NECC) and the South Equatorial Current (SEC) through reducing biases in the air–sea turbulence flux. Nevertheless, the SST assimilation has limited effects on improving the simulation of the spatial structure of these zonal currents in the tropical Pacific. The improvement of the wind stress curl over the tropical Pacific region mainly contributes to the improved simulated strength of the Pacific EUC, the NECC and the SEC. It also connects to the reduced biases in atmospheric convective precipitation and sea-level pressure induced by the reduction of the SST bias.