安庆市短历时暴雨强度公式推求

Study on Short-duration Rainstorm Intensity Formula for Anqing City

为推求受近年极端天气影响下的安庆市短历时暴雨强度公式,首先收集了安庆市1983~2012年的暴雨整编资料,采用年最大值法选取了10个历时下的雨强样本;然后采用P-Ⅲ型、指数和耿贝尔分布曲线进行适线,确定了P-Ⅲ型分布曲线为其理论频率曲线,得到了10个历时下各频率对应的雨强;采用高斯—牛顿法推求了各单一重现期下的暴雨强度分公式和所有重现期下暴雨强度总公式的参数。误差检验发现暴雨强度分公式的精度符合要求;而暴雨强度总公式的精度达不到要求,进而分析了精度达不到要求的原因。除个别历时下的雨强外,单一重现期下的新公式计算的雨强值均大于1981版暴雨强度分公式计算的雨强值,其中2年、5年一遇的雨强值比1981版公式计算的相应雨强值偏大1.4%~20.4%,计算结果与近年来安庆市受极端天气影响下的短历时降雨强度增大的趋势相一致。推荐使用暴雨强度分公式计算相应重现期下各历时的暴雨强度,其他重现期下的暴雨强度公式参数采用已知重现期下的暴雨强度分公式的参数内插获得。

For the derivation of short duration rainstorm intensity formula for Anqing City which is subject to ex treme weather recently. The data of rainstorm from 1983 to 2012 were collected, and 10 kinds of rainstorm samples were selected by using annual maximum sampling method. And then, the fitting and optimization of distribution curve were carried out with P-Ⅲ, exponential and Gumbel distribution. The theoretical rain intensity-duration-return period table was obtained by P Ⅲ distribution. Based on theoretical rain data, the parameters of three parameter and four-parameter formula were solved through Gauss Newton method. The results indicate that the parameters can meet the requirement of standard according to accuracy test for three-parameter formula for each recurrence period; however, the four-parameter rainstorm intensity formula for every recurrence period cannot meet the accuracy requirement, and the corresponding cau- ses were analyzed. Compared with the three parameter rainstorm intensity formula of 1981 version, most of rain intensi- ties of the new formula are higher than the corresponding rain intensity of the rainstorm intensity formula of 1981 ver sion; the rainfall intensities with recurrence periods of 2 a and 5 a are higher than corresponding value estimated through rainstorm intensity formula of 1981 version with 1.4% to 20.4%. The calculated results coincides the recent trends in Anqing City, in which short duration rainfall intensity is increasing under extreme weather. The three-parameter rain- storm intensity formula is commended for estimating the design rainfall intensity when the design return periods are con- sistent with the return period in the formula, and the rainfall intensity of other design return periods should be estimated by three-parameter storm intensity formula with its parameters obtained by interpolation.