场次降水与日降水差异对比

基于我国中东部18个气象站逐分钟降水数据,整理得到日降水与场次降水资料,统计日降水与场次降水的对应关系,并对比不同级别降水量的差异;同时,基于全国811个气象站08:00-20:00与20:00-08:00逐半日降水数据,按气象站(20:00-20:00)与水文站(08:00-08:00)2种日界标准整理出2套日降水资料,分析降水日界对日降水资料的影响.结果表明:大部分场次降水过程发生在同1日或者跨1日;场次降水量均值、90百分位、95百分位以及最大值4个指标的计算结果分别为日降水对应指标的1.2、1.2、1.3和1.5倍;将日降水资料计算得到的10、20、50、100a一遇重现期降水量分别乘以转换系数1.39、1.42、1.44和1.45,可与基于场次降水资料计算所得结果相当.气象站和水文站降水日界对大暴雨及其以下级别雨日数无显著影响,但对特大暴雨级别,气象站雨日数显著多于水文站;长江流域、珠江流域及西北大部,气象站标准重现期日降水量普遍大于水文站标准,而东南沿海地区、华北北部和东北北部,水文站标准重现期日降水量普遍大于气象站标准. 

Comparison of event and daily precipitations

One-minute rainfall data from 18 weather stations in middle and eastern China from 1961-2000 were used to derive event and daily precipitation values. Statistical relationships of event and daily precipitations were compared at different rainfall levels. Half-day rainfall of either 08:00-20: 00 or 20:00-8:00 from 811 weather stations nationwide were used to derive two datasets of daily rainfall according to different criteria of weather station (08:00-08:00) and hydrological station (20:00-20:00). Effects of daily boundary on characteristics of daily rainfall were analyzed. It was found that most events occured on the same day or across one day. The mean, 90％ percentile, 95％ percentile and maximum values of rainfall calculated from event precipitation data were found to be 1.2,1.2, 1.3 and 1.5 times of values calculated from daily precipitation. The 10 a,20 a, 50 a and 100 a return level precipitations calculated from daily rainfall data were found to be comparable to those calculated from event data after multiplying coefficients of 1.39,1.42,1.44 and 1.45,respectively. Daily precipitation boundary weather station criterion and hydrological station criterion had no significant impact on rainy days with rainfalls of ＜250.0 mm, whereas rainy days with rainfalls ≥250.0 mm based on the weather station criterion were significantly larger than those based on hydrological station criterion. Daily rainfall values in return levels based on weather station criterion were larger than those based on hydrological station criterion for Yangtze River Basin, Pearl River Basin and most of Northwest China,whereas the relationship is reverse for the southeast coast, northern part of North China and Northeast China.