Analysis of Correlation Between Water Vapor Content and Precipitation over North China

Based on airological observations from 12 meteorological stations in North China in recent 30 years,the temporal and spatial variation characteristic and correlation between water vapor content and precipitation over North China were analyzed by using means of linear trend method and the Singular Value Decomposition(SVD) technique.The results show that water vapor content over North China presented decreasing trend from southeast coast to northwest inland area,namely,wetting in southeastern but drying in northwest area;On the whole,the water vapor content over North China showed slight increasing trend,but precipitation as well as precipitation efficiency presented decreasing trend in recent 30 years.The precipitation efficiency was lower,that is to say,the development potential of water resources over North China was great.The first mode of SVD reflected close correlation between water vapor content and precipitation in North China,when annual mean water vapor content was less(more) than normal,annual precipitation in most area of North China was less(more) than normal.There was(no) obvious water vapor convergence to North China from South China Sea to Western Pacific,while there was(no) water vapor transport to North China in westerly belt in middle latitude during the year with more(less) precipitation,In addition,the vertical velocity became more stronger in more rainfall years at the level of 850 hPa.