Variations in precipitation extremes in the arid and semi-arid regions of China

Precipitation regimes have been predicted to shift to more extreme patterns that are characterized by heavy rainfall events and longer dry intervals. Spatiotemporal variation of precipitation extremes may significantly influence the local ecosystem, especially in the arid and semi-arid regions. This study investigated the variations in extreme precipitation indices across the arid and semi-arid land of China from 1960 to 2018. Spatial autocorrelation analysis was also conducted to evaluate spatial autocorrelations within the study area. There was generally an increasing trend of precipitation intensity, however, most stations in the low-altitude semi-arid regions showed non-significant trend. The frequency indices generally showed a decreasing trend in consecutive dry days, and an increasing trend in precipitation days in the arid land and high-altitude semi-arid regions, suggesting that the arid and high-altitude semi-arid regions are becoming wetter. Signals of decreasing precipitation intensity and frequency were still found, such as increasing trends in consecutive dry days in the stations from the low-altitude semi-arid regions, implying the possibility of increased drought risk at small spatial scale. The global Moran's I values indicated that the spatial autocorrelation of the trend in the low-altitude semi-arid region is high. The local Moran's I showed that the number of stations with wetting trend in the arid region were much higher than that in the semi-arid regions. These observations imply that the precipitation extremes in the arid and semi-arid regions of China are becoming more homogeneous. Hence, this study can serve as a useful reference to the policymakers and stakeholders for framing water resource and ecosystem management strategies in arid regions.

Automated summary

The study found an overall increasing trend in precipitation intensity, with most stations in low-altitude semi-arid regions showing non-significant trends. Frequency indices generally showed a decrease in consecutive dry days and an increase in precipitation days in arid and high-altitude semi-arid regions, indicating a trend towards wetter conditions in these areas. However, there were still some signals of decreasing precipitation intensity and frequency in certain stations in low-altitude semi-arid regions, suggesting an increased risk of drought at a small spatial scale.