A Bias-corrected Precipitation Climatology for China
中国降水观测误差分析及其修正

This paper presents the results of bias corrections of Chinese standard precipitation gauge(CSPG) measurements for wind-induced undercatch,trace amount of precipitation and wetting loss.Long-term daily data of precipitation,temperature,and wind speed during 1951-2004 at 726 meteorological stations in China were used for this analysis.It is found that wind-induced gauge undercatch is the greatest error in most regions,and wetting loss and trace amount of precipitation are important in the low precipitation regions in Northwest China.Monthly correction factors(corrected/measured precipitation) differ by location and by type of precipitation.Considerable inter-annual variation of the corrections exists in China due to the fluctuations of wind speed and frequency of precipitation.More importantly,annual precipitation has been increased by 8 to 740 mm with an overall mean of 125 mm at the 726 stations over China due to the bias corrections for the study period.This corresponds to 5%-72% increases(overall mean of 18% at the 726 stations over China) in gauge-measured yearly total precipitation over China.This important finding clearly suggests that annual precipitation in China is much higher than previously reported.The results of this study will be useful to hydrological and climatic studies in China.