东亚夏季风和中国东部夏季降水年代际变化的模拟

Numerical Simulation of Decadal Variations in the East Asian Summer Monsoon and Summer Rainfall in Eastern China

利用中国科学院大气物理研究所发展的第四代大气环流模式模拟了1970年代末东亚夏季风和相关的中国东部夏季降水年代际变化。结果表明,在给定的观测海温强迫下,模式能模拟出东亚夏季风的年代际减弱及相关的环流场变化,包括东亚沿海的偏北风异常以及西太平洋副高的形态变化,模式还较好再现了中国东部夏季降水的雨型变化,即长江流域降水偏多,而华北和华南偏少,但位置略偏南。基于奇异值分解(SVD)的分析表明,热带海洋变暖是这次东亚夏季风的年代际减弱的主要因素,这与太平洋年代际振荡(PDO)在1970年代末期的位相转变有关。此外,模式还较好模拟了长江流域的变冷趋势,进而减弱了海陆温差,使东亚夏季风减弱。

The fourth-generation atmospheric general circulation model, developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences, was used to simulate decadal variations in the East Asian summer monsoon （EASM） and in summer rainfall in eastern China during the late 1970s. It was shown that the model simulated well the decadal weakening of the EASM, a northerly anomaly along the East Asian coast, and changes in the western Pacific subtropical high. The model also reproduced the anomalous summer rainfall pattern in eastern China （i.e., an increase in the Yangtze River basin and a decrease in North China and South China）, except that the modeled pattern was located somewhat south of the observed pattern. Further analysis, using singular value decomposition, indicated that the decadal weakening in the EASM was mainly driven by warming in the tropical ocean, which is related to the Pacific decadal oscillation （PDO） phase transition in the late 1970s. The model also simulated the cooling trend in the Yangtze River basin, which led to a decrease in the thermal contrast between the continent and the ocean, and a weakened EASM.