气候系统模式FGOALS_gl模拟的赤道太平洋年际变率

The Tropical Pacific Interannual Variability Simulated with LASG/IAP Climate System Model FGOALS_gl

本文分析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)发展的气候系统模式FGOALS_gl对赤道太平洋年际变率的模拟能力。结果表明,FGOALS_gl可以较好地模拟出赤道太平洋SST异常年际变率的主要特征,但模拟的ENSO事件振幅偏大,且变率周期过于规则。耦合模式模拟的气候平均风应力在热带地区比ERA40再分析资料的风应力强度偏弱30%左右,由此引起的海洋平均态的变化,是造成模拟的ENSO振幅偏强的主要原因。FGOALS_gl模拟的ENSO峰值多出现在春季或夏季,原因可归之于模式模拟的SST季节循环偏差。耦合模式可以合理再现ENSO演变过程,但观测中SST异常的东传特征在模式中没有得到再现,这与模拟的ENSO发展模态表现为单一的"SST模态"有关。模拟的ENSO位相转换机制与"充电—放电"概念模型相符合,赤道太平洋热含量的变化是维持ENSO振荡的机制。在ENSO暖位相时期,赤道中东太平洋与印度洋—西太平洋暖池区的海平面气压距平型表现为南方涛动型(SO型),200hPa位势高度分布表现为太平洋—北美遥相关型(PNA型)。

The authors evaluate the performance of the fast coupled version of LASG/IAP climate system model FGOALS_gl on simulating the interannual variability in the tropical Pacific.Compared with the observations,the main characteristics of the interannual variability in the tropical Pacific Ocean is reasonably reproduced.Nonetheless,the coupled model also shows clear biases.The amplitude of El Nino-Southern Oscillation（ENSO）is overestimated.The model also fails in simulating the irregularity of ENSO cycle.The overestimation of ENSO amplitudeis mainly caused by the weaker climate mean trade wind and the associated mean state bias of the ocean.The phase locking of ENSO appears in boreal spring and summer in the model,which is attributed to the bias of sea surface temperature（SST）annual cycle in the tropical Pacific Ocean.The observed eastward propagation of SST anomalies is not evident in the model,and this is related to the simulated single developing mode of ENSO（SST-mode）.The negative feedback of ENSO is explained by the＂Recharge-Discharge Oscillator＂theory,in which the change of the equatorial Pacific Ocean heat content acts as an important transitioner for ENSO.The sea level pressure anomalies feature a Southern Oscillation（SO）-like pattern in boreal winter associated with El Nino events,and the corresponding geopotential height at 200hPa exhibits a Pacific-North America（PNA）teleconnection pattern.