Estimation of summer precipitation in China based on wind data from NCEP

Based on the wind data from NCEP,an estimation model for calculating the summer precipitation in China is presented. The required monthly prevailing wind data is obtained through surface pressure,zonal and meridional wind data from NCEP during 1971- 2000. The cosine value of the separation angle between the prevailing wind direction and the macro- topographic orientation is taken as slope factor to identify the windward slopes and leeward slopes. Then a multiple stepwise regression equation is developed to estimate summer precipitation in China according to precipitation data from observation gauges,digital elevation model( DEM),topographic orientation,etc,and the spatial distribution of the monthly and total summer precipitation from 1971 to 2000 in China is available. Results produced by validation and comparative analysis indicate that in summer the mean absolute error is 27 mm and the mean relative error is about 11. 8%. The estimated precipitation distribution is reasonable because the difference in precipitation between the windward slope and the leeward is obvious. It is also able to qualitatively and quantitatively describe the real distribution of summer precipitation in China.