中国降水观测误差分析及其修正

A Bias-corrected Precipitation Climatology for China

在1980s乌鲁木齐河流域进行的降水误差观测试验结果基础上,依据我国726个气象站1951～2004年逐日观测资料,对降水的动力损失、微量降水以及湿润损失进行系统的修正,以期获得更准确的长系列降水资料,为区域乃至全球水热循环过程和水文学研究提供基础资料。修正结果表明,在大部分地区由风速作用引起的动力损失是主要的误差来源,但在降水较少的地区湿润和微量降水观测损失也起着重要作用,全国726个台站年降水修正量在8～740 mm之间,平均约125 mm,相应的修正幅度在5%～72%,平均约18%。从时间看,冬季修正系数大于夏季,但冬季修正量小于夏季;从空间分布看,西北地区年修正量一般小于50 mm,东南地区大于100 mm,总修正系数由西北向东南地区减少,其中西北地区大于30%,而西南地区小于20%,这一修正系数高于全球的11%左右的平均修正量。

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 -72% increases （overall mean of 18% at the for the study period. This corresponds to 5% 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.