中国东部夏季降水的年代际变化格局——观测与CESM控制试验模拟结果的对比

根据1961-2005年中国东部389站的夏季降水观测资料,以及通用地球系统模式（the community earth system model,CESM）在固定边界条件驱动下的650年控制试验模拟结果,采用经验正交函数分解和功率谱分析等方法,辨识了中国东部夏季降水年代际变化的主导格局。观测分析与CESM的控制试验模拟结果均表明：中国东部夏季降水年代际变化的主导空间型为“南北反相”（大致以淮河流域为界）和由南到北的多带相间分布（长江流域、东北同相但与华南、华北反相）格局。对比证明：在无任何外强迫变化下,CESM可模拟出观测到的1961-2005年中国东部夏季降水年代际变化的主导空间型和相应的时间位相转折特征。这为深入辨识区域降水年代际异常的主控因子,分析气候系统外强迫变化和内部变率对中国降水年代际变化的影响机制提供了重要依据。

Spatial pattern of decadal variation of summer precipitation in Eastern China: Comparison of observation and CESM control simulation

Using observed summer precipitation data from 389 sites for the period of 1961-2005, and a 650-year control simulation by the Community Earth System Model (CESM) with fixed pre-industrial external forcing, the dominant patterns of decadal variation of summer (June, July, August) precipitation over eastern China were analyzed with the EOF and Power Spectrum. The EOF analysis of both observed data and simulated data shows that the major patterns of decadal variation of summer precipitation over eastern China are a dipole pattern divided by the Huaihe River and a four zonal bands alternate with each other centered at South China, the Yangtze River Valley, North China Plain and Northeast China. Comparison between observation and simulation demonstrate that the CESM with the fixed external forcing reproduced well the above mentioned patterns and temporal alternations of phases of decadal variation of summer precipitation over eastern China during 1961 to 2005. This finding provides the knowledge for understanding the main causes of regional decadal precipitation anomalies and analyzing the influences of external forcing and internal variability on decadal variation of precipitation over China in future study.