用反射率因子垂直廓线联合雨量计校准估测夏季区域强降水

ESTIMATION AMOUNT OF SUMMER REGIONAL HEAVY RAINFALL USING THE AVERAGES OF RADAR VPRs TOGETHER WITH RAIN GAUGE ADJUSTMENT

提出了一种使用平均雷达反射率因子垂直廓线(VPR)联合雨量计校准估测地面降水的方法。选用2002年、2003年夏季长江中下游地区的宜昌和合肥新一代S波段多普勒雷达在几次大范围强降水过程中的部分时段体积扫描强度数据和周边100 km范围内整理成10 min一次的雨量资料,计算了区域上空短时平均VPR在地面的可能反射率因子值,并用此值反演降水,计算相对误差。同时,还分析了超短时强降水地区实时VPR的特征。结果表明:用最小二乘曲线拟合VPR数值,并联合雨量计平均校准因子估测降水,在大部分区域比较合理。与实测的降水比较可以看到,这种方法对提高估测区域性降水的精度都有效果;对于强对流性降水区域,只须用拟合法得到的地面反射率因子值估测地面降水。通过分析超短时强降水对应区域的实时VPR特征,有利于在无地面雨量计的地区通过分析VPR的特征来估测降水量的大小,结合其他要素分析降水的发展变化。

A method of estimating precipitation using gauge adjustment is presented. Focusing on the the averages of radar VPRs together with several events of heavy rainfall occurred in the mid-lower reaches of the Yangtze river in the summer of 2002 and 2003, the radar reflectivity factor data of volume-scan mode acquired by the CMA new generation S-Band radar deployed in Yichang and Hefei, and the corresponding 10-min average of gauge precipitation records in the range of the 100 km radius centered at above radar locations are used to calculate possible short-term average of VPRs at the ground-level, and are further to retrieve the precipitation amount and its relative errors. These objective data are also used to analyze characteristics of real-time VPRs in 10 min heavy rainfall. The precipitation amount, which is estimated by using the averagely adjustments of gauge records together with the fitted VPRs based on the least square method （LSM）, is reasonable at surface level over a great part of a certain region. Compared with gauge records, the proposed method shows its capability to improve the precision of precipitation estimation in a regional scale, however, for the case of intensive convective precipitation, only the LSM is applicable. Characteristics of VPRs in a short time intensive heavy rainfall are helpful to estimate the amount of rainfall over a region without the gauge. Additionally, with combination of other data sources, characteristics of VPRs can be used to analyze the evolution of the precipitation process.