利用国家气象信息中心1961 -2020年中国黄土高原地区64个站点逐日昼夜降水数据， 将黄土高原分为两个区域（季风区和西风区）， 并使用线性趋势、 t检验等方法分析了两个区域两个季节（湿季和干季）昼夜降水日数和降水量的变化特征。结果发现， 黄土高原季风区和西风区昼夜降水均有显著的季节差异， 季风区湿季（5 -9月）昼夜降水日数占全年的比例都达60%、 降水量到75%以上， 西风区湿季昼夜降水日数占全年的比例则都近70%、 降水量到80%以上。黄土高原有西风区变湿、 季风区变干的趋势； 其中最为显著的特征是， 西风区湿季白昼降水量增加的站点高达77.8%， 干季昼夜都有超过50%的站点降水量增加； 季风区湿季昼夜降水日数和降水量减少的站点分别超过80%和50%， 干季则分别超过95%和80%。

Based on the day and night precipitation data of 64 stations in the Loess Plateau of China from 1961 to 2020 from the National Meteorological Information Center， the Loess Plateau is divided into two regions （monsoon region and westerly region）.The variation characteristics of daytime and nighttime precipitation days and precipitation in the two regions in two seasons （wet-season and dry-season） were analyzed using methods such as linear trend and t test.The main conclusions are as follows： There are significant seasonal differences in daytime and nighttime precipitation between the monsoon region and the westerly region of the Loess Plateau.The number of daytime and nighttime precipitation days in the wet-season （May-September） in the monsoon region accounts for 60% of the whole year， and the precipitation is more than 75%.In the westerly region， the proportion of daytime and nighttime precipitation in the whole year is nearly 70%， and the precipitation is more than 80%.The Loess Plateau tends to get wet in the westerly area and dry in the monsoon area.Among them， the most prominent feature is that in the westerly region， The number of stations which measured increase in daytime accounts for 77.8% of the total.in the wet-season， and more than 50% in the dry-season.In the monsoon area， the number of stations in daytime and nighttime which measured decrease in precipitation days and precipitation account for more than 80% and 50% respectively in the wet-season， and more than 95% and 80% respectively in the dry-season.