Characteristics of Dry and Wet Variations in the Northwest China and Their Future Predictions

Based on various meteorological elements, such as precipitation, soil moisture, runoff and drought index, the evolution of dry and wet characteristics in Northwest China over the recent 60 years is systematically analyzed and studied, and the future changes are forecasted using the latest multimodel simulation results of the Coupled Model Intercomparison Program Phase 6 (CMIP6). The results show that the precipitation, soil moisture, and runoff in Northwest China in the recent 60 years showed a spatially decreasing pattern from southeast to northwest. Precipitation and runoff in the cold season are significantly lower than those in the warm season, but the differences in soil moisture and drought index in the cold and warm seasons are not significant. The annual precipitation, soil moisture, and drought index in Northwest China showed significant increasing trends, with increasing rates of 5.07 mm/10 a, 3.89 mm/10 a, and 0.26 /10 a, respectively, and especially after 2000, the increasing trends became increasingly obvious. The largest humidification range mainly occurred in the western part of Northwest China. The humidification range in the warm season was higher than that in the cold season. However, the runoff showed an obvious downward trend before 2000 and increased significantly after 2000. In the future climate change scenario, the northwest region shows an increasing trend of humidification in the middle of the 21st century (2031–2060) and the later period (2071–2100), and the degree of humidification in the later period of the 21st century is more significant. The humidification under the high-emission scenario (SSP5-8.5) is more obvious than that under the medium-emission scenario (SSP2-4.5). The study results provide a reference for the impact assessment of climate change in Northwest China.