基于SPEI指数分析河西走廊气象干旱时空变化特征

利用河西走廊1965-2017年21个气象站点逐日气象数据，基于Penman-Monteith蒸散模型计算不同时间尺度的SPEI，分析河西走廊气象干旱的变化趋势、发生频率和持续时间等时空变化特征。结果表明：（1）近53a来河西走廊月、季、年尺度SPEI均呈显著上升趋势，即干旱有显著减弱趋势，但个别站点干旱持续时间较长，其中武威站在2013年持续时长达到11个月；（2）河西走廊四季均存在变湿趋势，且冬季变湿显著，其中春、夏、秋季干旱呈不稳定变化，而冬季在1989年前后发生突变，由干旱向湿润突变；（3）河西走廊干旱的空间分布具有明显的区域特征，干旱区域主要集中在西北部，湿润区域主要集中在南部；（4）不同时间尺度各等级干旱发生频率的变化规律具有一致性，轻中旱发生频率远高于重特旱，且年、季尺度重特旱发生相对高频区空间分布特征与轻中旱正好相反。总之，近53a来河西走廊干旱呈减弱趋势，有利于当地的农业生产开展和生态环境改善，但该区域气候变化较复杂，需要注意局部干旱情况。

Analysis of Spatial-temporal Variation Characteristics of Meteorological Drought in the Hexi Corridor Based on SPEI Index

Using the daily meteorological data of 21 meteorological stations in the Hexi corridor from 1965 to 2017, SPEI at different time scales was calculated based on the Penman-Monteith evapotranspiration model, and the temporal and spatial variation characteristics of meteorological drought in the Hexi corridor, such as the change trend, occurrence frequency and duration, were analyzed. The results showed that: (1) in the past 53 years, the SPEI of the Hexi corridor showed a significant upward trend on the monthly, seasonal and annual scales, which indicated that the drought had a significant weakening trend, but the drought lasted for a long time at individual stations, and the drought lasted for 11 months in 2013 in Wuwei. (2) The Hexi corridor had a trend of wetting in four seasons, and it was significantly wet in winter. Among them, the in spring, summer and autumn presented unstable drought changes, while the sudden change in winter around 1989 indicated the trend from drought to wet. (3) The spatial distribution of drought in the Hexi corridor had obviously regional characteristics. The arid area was mainly concentrated in the northwest, and the humid area was mainly concentrated in the south. (4) The frequency variety law of different grades drought occurance at different time scales was consistent .The frequency of mild to moderate droughts was much higher than that of severe and extreme droughts, and the spatial distribution characteristics of relatively high frequency areas of severe and extreme droughts on the annual and seasonal scales were opposite to those of mild to moderate droughts. Generally, the drought in the Hexi corridor had weakened in the past 53 years, which was beneficial to the local agricultural production and ecological environment. However, the climate change in this region is complex, and local drought needs to be paid attention to.