Intensity and spatial heterogeneity of design rainstorm under nonstationarity and stationarity hypothesis across mainland China

Understanding the trend characteristics of design rainstorm and spatial heterogeneity of extreme precipitation is of great importance to reduce disasters induced by rare extreme precipitation. Using a high-resolution (0.5° × 0.5°) daily gridded data set of precipitation across mainland China from 1961 to 2013, this study investigated the historical changing trend and spatial heterogeneity of design rainstorm using the 30-year moving window method (30YM). Differences in the quantification of the design rainstorm were compared for the use of the 30YM and the 30-year-based increasing window method (30YBI). The results show that a significant increasing intensity but no spatially uniform trend of design rainstorm can be observed across mainland China based on the 30YM analysis. The south, east, and northeast China mainly showed an increasing trend, but the southwest and north China presented a decreasing trend. The spatial heterogeneity of the design rainstorm was greatly enhanced if the nonstationarity assumption was adopted on the national scale. The heterogeneity showed an increasing trend mainly in southeast, north, northeast, and northwest China, and a decreasing trend in southwest and west China, indicating significant regional variation in spatial heterogeneity. For most areas of mainland China, especially for southeastern, northeastern, and western China, use of the most recent precipitation sub-series to quantify the design rainstorm may weaken the potential nonstationarity and guarantee the safety of infrastructure in these areas where design rainfall increases.