Features of Moisture Transport Associated with the Precipitation over North China during July-August

The July-August Asian monsoon moisture transport and its relationship with the rainfall over North China have been investigated using NCEP/NCAR monthly mean reanalyses and precipitation data of 160 stations in China over 1951-2005.Results show that different moisture paths connect with different regional rainfall in North China,respectively.The features of moisture fluxes in North China rainy season with more rainfall are quite opposite to that with less rainfall.Experience Orthogonal Function(EOF) analysis describes that anomalous influxes through every moisture path to North China correspond to the positive rainfall anomaly over this region,and vice versa.The Asian monsoon contributes much more than the westerlies in terms of vapor transfer into the North China.Both moisture influxes are closely related to the rainfall in North China on the interdecadal time scale.The moisture transfer by Asian monsoonal currents underwent an abrupt weakening at the end of the 1970s which was in connection with the distinct decrease of precipitation over North China from the beginning of the 1980s and gave relative emphasis to the westerly moisture transfer associated with rainfall over North China.