The Interdecadal Variation of Precipitation Pattern over China during Summer and Its Relationship with the Atmospheric Internal Dynamic Processes and Extra-Forcing Factors

Analyses of the monthly precipitation of 160 stations over China during 1951-2006,50-yr NCEP/NCAR reanalysis dataset and monthly 1°× 1° sea surface temperature data of Hadley center during 1900-1999 reveal remarkably different interdecadal variation of precipitation pattern between eastern and northwestern China in their temporal-spatial distributions.Since the early 1980s the precipitation over the Yangtze River valley became more than climatic average and the precipitation over Huabei Plain became less than climatic average,and since the late 1980s the precipitation over northwestern China became more than climatic average.The contributions of the atmospheric internal dynamic processes and the extra-forcing factors(such as sea surface temperature) to the interdecadal variations of precipitation between eastern and northwestern China are different.The interdecadal variations of precipitation over eastern China during summer are related to the temporal evolution of the Pacific Decadal Oscillation(PDO) by using empirical orthogonal function(EOF) method and regress analysis.The interdecadal variations of precipitation over northwestern China during boreal summer are related to the interdecadal variation of anomalous perturbation kinetic energy of Rossby wave along East Asian westerly jet in midlatitudes.Since 1988 the perturbation kinetic energy of Rossby wave along East Asian westerly jet in mid-latitudes became weaker and meantime the precipitation over northwestern China became more than climatic average.