不同截取水平下咸阳市干旱特征

Study on Drought at Different Levels in Xianyang

根据1959-2005年咸阳市11个测站的降水资料,采用统计分析法,推导出干旱历时的概率分布参数计算公式,取实测序列的均值作为截取水平,对咸阳市11个测站的降水序列进行干旱历时概率分布参数的求解。然后,采用全历时重现期法,对咸阳市干旱历时重现期在两种不同干旱等级(平水年和偏枯年)对应的截取水平进行了精确计算。对于干旱烈度及其重现期,则假定实测序列服从正态分布,且该序列干旱烈度服从Gamma分布,同样,选取两种截取水平,计算咸阳市11个测站降水序列的干旱烈度概率分布参数以及干旱烈度重现期。结果表明:采用偏枯状态对应的截取水平计算的重现期能更好地反映区域干旱发生的内在规律性。

Based on the precipitation data observed by 11 observation stations in Xianyang in 47 years from 1959 to 2005,this paper discusses the probability distribution of duration and intensity of drought at different levels in Xianyang using the method of statistical analysis after deriving the calculation formula of probability distribution of drought duration in Xianyang. The reoccurring periods of drought duration at two different levels （ normal years and dry years） in Xianyang are accurately calculated using the reoccurrence method. For the drought intensity and its reoccurring periods,it is assumed that both the measured series are in a normal distribution and the drought intensity of these measured series is in gamma distribution. Similarly,the two different drought levels （ normal years and dry years） are used to calculate the reoccurring periods of drought intensity and the probability distribution parameters of drought duration of precipitation series at the 11 observation stations in Xianyang. The results show that the threshold level of dry years can be used to ideally reveal the drought occurrence in Xianyang.