陕西省近47a来降水变化分析

利用1961—2018年黄土高原区域57个基准站逐月降水资料，引入标准化降水指数（SPI）以及多个旱涝评估指标研究了黄土高原旱涝频率时间分布特征、旱涝趋势演变特征和旱涝范围、强度演变特征等，并得出了年和夏季旱涝频率、趋势的空间分布特征以及不同地形区分布特征。分析研究表明，近58 a黄土高原旱的频率高于涝，各季中夏旱、夏涝频率最高，重度及以上旱以夏、春居多，重度及以上涝以春、秋居多；研究区各时间区间中季、月均以趋于干旱为主，近58 a总体趋于干旱；20世纪60到80年代旱涝交替出现，90年代干旱开始增多，干旱强度加剧，21世纪00年代开始干旱有所缓和，10年代由旱转涝；研究区域逐年干旱站次比和干旱强度先趋于增大后减小，雨涝站次比和雨涝强度则先趋于减小后增大，90年代干旱最重，60年代雨涝最重；研究还得出了旱涝发生高频区及变化趋势显著区，夏季多起伏地形旱涝频率总体高于平缓地形。

How Many Check Dams Do We Need To Build on the Loess Plateau

Based on the monthly precipitation data of 57 stations in the Loess Plateau from 1961 to 2018, this paper introduces the standardized precipitation index (SPI) and several assessment indicators of droughts and floods to study the temporal characteristics of the frequencies, the trend characteristics, the changes of the range and intensity of droughts and floods in the Loess Plateau. The spatial and topographical distribution characteristics of annual and summer frequencies and variable trend of droughts and floods are also obtained. The research shows that the droughts frequency of the Loess Plateau is higher than that of floods, the frequencies of summer droughts and summer floods are the highest among the seasons, severe droughts often occur in summer and spring, severe floods often occur in spring and autumn. Overall, the Loess Plateau tends to be arid in the past 58 years, and the trends are also the same in seasons and months. Droughts and floods alternately appeared in the 1960s and 1980s, the number and the intensity of droughts increased in the 1990s. Since the beginning of the 2000s, the drought has eased, and there is a change from drought to flood in the 2010s.The ratio of drought stations and the intensity of drought tend to increase and then decrease, while the ratio of flood stations and the intensity of flood tend to decrease and then increase. In the 1990s, the drought was the heaviest, while in the 1960s, the flood was the heaviest. The zone where droughts and floods happened frequently and the area of significant trend are also obtained by the research, frequencies of droughts and floods in the undulating terrain are generally higher than that in the gentle terrain in summer.