1960-2009 年河西地区极端干湿事件的演变特征

采用1960-2009 年甘肃省河西地区13 个观测站逐日气象资料，应用FAO Penman-Monteith 模型计算各气象站年和月的地表湿润指数，进行标准化后统计极端干湿事件频率。采用反距离加权插值法、Mann-Kendall 法及Morlet 小波分析对河西地区极端干湿事件的时空演变特征进行探讨。结果表明：近50 a，河西地区极端干旱和湿润事件频率在波动变化中分别呈减少和增加趋势，其倾向率分别为-0.009 次/a、0.019 次/a，且2000 年以后，趋势更为显著；空间变化上，区域内极端干旱事件倾向率的空间差异整体呈减小趋势，以2000-2009 年的空间差异为最小。20 世纪60 年代，大部分区域极端干旱事件频率增加区与极端湿润事件频率减少区相对应，而极端干旱事件频率减少区与极端湿润事件频率增加区相对应。突变分析表明，极端干旱和湿润事件频率分别在1998 年和1986 年发生突变。平均风速、平均气温和相对湿度是影响河西地区极端干湿事件的主要气象因子，极端干旱和湿润事件频率的主周期分别为19 a和26 a。

Temporal and Spatial Characteristics of the Extreme Drought and Wet Events Changes in Hexi Area from 1960 to 2009

Based on the daily data of the 13 meteorological stations in Hexi Area of Gansu Province from 1960 to 2009, we calculate the surface humid indexes of months and years, as well as the extreme drought and wet events frequency. With the method of ArcGIS IDW interpolation, Mann-Kendall, Morlet wavelet, etc, the temporal and spatial variations of extreme drought and wet events frequency are discussed, along with its impact factors. The results show: frequency of the overall trend of extreme drought and wet events fluctuantly decreased and increased from 1960 to 2009, respectively. After the year 2000, the trend became more obvious. The linear trend of the extreme drought and wet events frequency were about -0.009/a and 0.019/a, respectively. For spatial variation, the space difference of extreme drought event tendency was not obvious, especially during 2000-2009. In the 1960s, the area that extreme drought events increased corresponded to the area which extreme wet event reduced and the area that extreme drought events reduced corresponded to the area which extreme wet event increased. The abrupt change of extreme drought events frequency and extreme drought events frequency happened in 1998 and 1986, respectively. The annual mean wind speed, annual mean temperatures and relative humidity were the dominant factors in influencing extreme drought and wet events. The major cycle of extreme drought and wet events frequency were changing respectively with 19 a and 26 a.