海表温度异常影响东亚夏季风年代际变化的数值模拟

采用1950-2000年逐月观测的不同海域(全球、热带外、热带、热带印度洋-太平洋、热带印度洋及热带太平洋)海表温度分别驱动NCAR CAM3全球大气环流模式,进行了多组长时间积分试验,对比ERA-40和NCEP/NCAR再分析资料,讨论了这些海域海表温度异常对东亚夏季风年代际变化的影响。数值试验结果表明:全球、热带、热带印度洋-太平洋和热带太平洋海表温度变化对东亚夏季风的年代际变化具有重要作用,均模拟出了东亚夏季风在20世纪70年代中后期发生的年代际减弱现象,以及强、弱夏季风年代夏季大气环流异常分布的显著不同,这与观测结果较一致,表明热带太平洋是影响东亚夏季风此次年代际变化的关键海区;利用热带印度洋海表温度驱动模式模拟出的东亚夏季风在20世纪70年代中后期发生年代际增强现象,即当热带印度洋海表温度年代际偏暖(冷)时,东亚夏季风年代际增强(减弱),与热带太平洋海表温度变化对东亚夏季风年代际变化的影响相反;热带太平洋海表温度年代际背景的变化对东亚夏季风在20世纪70年代中后期的年代际减弱有重要作用。

Numerical simulation of SSTA effect on interdecadal variation of East Asian summer monsoon

The effects of regional SST(sea surface temperature) anomaly on interdecadal variation of East Asian summer monsoon(EASM) are investigated based on the observed monthly SSTs in different sea waters(global,extra-tropical,tropical,tropical Indian Ocean-Pacific,tropical Indian Ocean,and tropical Pacific) during 1950-2000.The observed SSTs are used to drive the NCAR CAM3 global atmospheric circulation model in a separate way,followed by long-term multiple group integrations in comparison to ERA-40 and NCEP/NCAR reanalysis data.Numerical simulations show that the SST changes of global,tropical,tropical Indian Ocean-Pacific,and tropical Pacific exert important impacts upon the interdecadal variability of EASM,reproducing the observed interdecadal weakening happened in the mid-late 1970s.Their simulated summer circulation anomalies in the strong and weak EASM years differ greatly,in better agreement with observations.Tropical Pacific is the key region to impact the interdecadal variation of EASM.Extra-tropical SSTA has weaker effect on the interdecadal variation of EASM.The tropical Indian SST-driven simulations reveal an interdecadal strengthening of EASM since the mid-late 1970s opposed to the impact of tropical Pacific SSTA,i.e.,the EASM interdecadal strengthening(weakening) is responded to the interdecadal warm(cold) SSTA in the tropical Indian Ocean.As a background,the interdecadal variation of SST in tropical Pacific has important effect upon the interdecadal weakening of EASM in the mid-late of 1970s.