利用河西地区经过严格质量控制的13个站点1958—2015年的日降水资料,从年度和季节尺度,定义分析了最大连续降水事件的日数、降水量和降水强度的9个指标,应用标准化序列法描述指标随时间的演变情况,使用Mann-Kendall趋势分析法在95%置信水平下进行了趋势的显著性检验,以研究该地区最大连续降水事件的时空变化特征。结果 表明:(1)河西地区最大连续降水日数发生以1～2 d为主,近年来,夏季日数增长,秋季日数减短,但整体来看,年、夏和秋季最大连续降水日数均有增长,但中西部更加明显。(2)最大连续降水量在夏季略有下降,秋季增多明显,且河西中西部地区夏秋分化更明显,东南部地区以下降为主。(3)年、夏和秋季4～6 d的最大连续降水强度最大,降水强度随着最大连续降水日数的增加略有上升。总体上近年来河西地区最大连续降水日数增加,降水强度上升,表明河西地区具有湿润化趋势,而秋季湿润趋势更明显。研究结果有助于进一步了解西北干旱区的极端降水变化特征和区域气候变化应对情况。
Based on the daily precipitation data which quality was control from 13 rain stations in Hexi Area during 1958—2015, nine precipitation extreme indices relative to days of consecutive wet events, precipitation and precipitation intensity were defined, the spatial and temporal possibility variations of maximum consecutive wet days in the whole year, summer and fall seasons were studied, the maximum consecutive wet events' spatial and temporal variability of the study area was examined by using the Mann-Kendall method for trend analysis and at the 95% confidence level for trend significance test. The results show that:(1)one or two days consecutive wet days occurred most frequently in Hexi Area; the days of maximum consecutive wet days increased in summer and reduced in fall in recent years, but all increased in whole years;(2)the precipitation of consecutive wet days had reduced in summer and more significantly increased in fall, the differentiation of wet days between summer and autumn was obviously in midwest of Hexi area, the reduction of precipitation of consecutive wet days mainly occurred in the southeast;(3)the maximum precipitation intensities mostly occurred in the events of onsecutive precipitation with the duration of four to six day, and the precipitation intensities increased with the increase of the number of days of maximum consecutive wet days. In all, the number of days of maximum consecutive wet days increased while precipitation intensities increased too in Hexi Area in recent years, showing the wet tendency and more obvious wet tendency in fall. These results of this study are helpful to further understand the characteristics of extreme precipitation change and regional climate change response in the northwest arid region.
