Spatial/temporal variations of summer precipitation anomalies in North China and their relations to atmospheric circulation.

Based on the monthly rainfall data at 160 stations in China during 1951—2005,the spatial-temporal variations of summer rainfall anomaly at 17 stations in North China are studied,and the atmospheric circulation factors influencing the rainfall anomaly over North China are discussed.Results show that the total summer rainfall tendency of North China decreases significantly during 1951—2005 with the interannual variations of quasi-three,quasi-six,quasi-eight years and the interdecadal variation of 17—19 years.The summer rainfall in North China is usually opposite to the rainfall in Southern Yangtze River and South China in phase.The summer rainfall in North China is more than the normal when the northeast wind in the Baikal region,the southwest air current over Indo-China Peninsula and westard air current at the north side of Tibetan Plateau are stronger than the normal at 850 hPa,meanwhile the subtropical high is weaker and lies northward and westward of it normal position,and the cold air stronger,and summer monsoon more active with abundant vapor at 500 hPa.