关键词: 华北地区, 降水蒸发差, 东亚季风, 大气环流

Abstract: The variations of the Difference between Precipitation and Evaporation (DPE) in the North China were analyzed,by using the trend analysis and Mann-Kendall test methods. The interdecadal differences of distribution of wind,air pressure,relative humidity and temperature over East Asia area were compared. The results showed that the interdecadal transition of the DPE changed from increasing to decreasing in the North China in 1977,mainly due to the precipitation variations. There was a positive correlation between the variations of DPE in the North China and the Asian meridional circulation indexes,and a negative correlation with the Asian zonal circulation indexes. These correlations were with different significances in the different stages. Before and after 1977,the southwest monsoon changed from strengthening to weakening at 850hPa over the East Asia area. The distribution of air pressure anomalies changed from low to high at middle and high latitude area. The relative humidity anomalies change from positive to negative value at 850hPa,while the air temperature departure change from negative to positive value at 1000hPa. The main reasons of continual decreasing of the DPE in the North China since 1978 were the weakening of the East Asian summer monsoon intensity,the decreasing of the water vapor transportation from the tropical area,and the decreasing of the summer precipitation in the North China. The drought tendency farther extended was the main causes of the East Asian winter monsoon intensity weakening,the strengthening of Asian zonal circulation countercheck which affected the cold air from polar region toward south,the air temperature rise up and the evaporation increasing in the North China. The conjunctive actions of the atmosphere circulation over East Asia area on the precipitation and air temperature induced the interannual and interdecadal variations of the DPE in the North China.

Key words: North China, North China, Precipitation-evaporation difference, East Asian monsoon, Atmosphere circulation