自动与人工观测降雨量的差异及相关性

The Difference and Relativity Between Rainfall by Automatic Recording and Manual Observation

利用全国627个基准、基本站2005年自动与人工雨量业务观测资料,分析了业务上自动与人工观测的降雨量的差异以及引起差异的原因,并分析了自动观测与人工观测的降雨量的相关性。结果表明:自动观测比人工观测的日降雨量平均偏高0.12 mm,标准差为0.70 mm,相对偏高1.42%。627个站中,80%的站自动与人工观测的年降雨量差值在5%以内;近4%的站年降雨量差值在10%以上。年降雨量相对差值较大的站,其年降雨量均较小。空间采样差、20:00(北京时)定时观测中人工与自动观测时间的不一致以及其他突发事件均会导致自动与人工测量的日降雨量的差异,甚至显著差异。由于观测仪器不同引起的降雨测量系统误差差别,导致自动与人工观测降雨量的系统偏差。自动观测与人工观测的日降雨量呈线性相关,相关系数为0.9988。

Automatic Surface Observation System （ASOS） is set up by China Meteorological Administration （CMA） about 2000. Main surface meteorological parameters start to be automatically measured at about 600 base stations, 1200 ordinary stations in CMA by the end of 2005. Since both field intercomparison experiment results and parallel comparison observation results show that the difference is much great between the amount of rainfall measured by commonly used rain gauges （manual observation） and that measured by tipping-bucket rain gauges （automatic recording）, commonly used rain gauges are still kept on rainfall measurement manually twice a day in China surface meteorological observation operation, though automatic measurements of rainfall have been implemented to record hourly precipitation totals at a large number of stations at present. What the difference and relativity are between the amount of rainfall measured by automatic recording and by manual observation in observational operation remains a question to many meteorologists. Based on 55641 operational rainfall observations respectively by automatic way and by manual way at 627 national base stations in 2005, various analyses are cartied out on the rainfall observation difference, the difference and relativity between above two observation methods. In the rainy season, when there is no rain by manual observation, there is no rain by automatic recording at each station. The average daily rain amount observed by automatic way is 0.12 mm （or 1.42 % ） more than that by manual way. The standard deviation of the difference is 0.70 mm. In the 55641 rainfall comparison observations, 26.2% daily data observed in the two ways is identical, 30.8 % daily data observed by automatic way are less, 43.0 % daily data observed by automatic way are more than the manual way. The annual rainfall measured by automatic recording is more than that by manual observation at 70 % base stations. There are 80 % stations whose difference values in annual rainfall respectively observed in the two ways are less than 5 % , and the difference values are above 10 % at 4 % stations. Comparing to field experiment results in the two observation methods in early 1990s, the difference of operational annual rainfall observations respectively in the two ways is obviously improved at the 627 base stations in 2005. In general, the more the difference value in annual rainfall, the less the annual rainfall in a station. The distribution difference of rainfall in space, the difference in measurement time of the two observation ways at 20：00 and other urgent events can result in the rainfall difference in daily data, but they have no systematic effect on accumulative total. Different observation instruments and likely low quality can lead to the systematic deviation in above comparing observations. The daily rainfall by automatic recording is obviously linearly related with that of manual observation and the correlation coefficient is 0. 9988.