Background Rainfall erosivity is the potential capacity of water erosion caused by rainfall. It is an important factor in soil erosion models including USLE (Universal Soil Loss Equation), RUSLE (Revised Universal Soil Loss Equation) and CSLE (Chinese Soil Loss Equation). Soil erosion is relatively serious in Henan province, and the research of rainfall erosivity has been paid much attention. However, relevant studies are far from enough. Analyzing the spatial distribution and trend variation of half month, seasonal and annual rainfall erosivity may provide scientific basis for regional soil erosion assessment and prevention.

Methods Based on the daily rainfall data of 90 meteorological stations in Henan province from 1981 to 2020, this paper used the daily rainfall erosivity calculation model to detect the spatio-temporal patterns and variation of rainfall erosivity through Moran index, trend coefficient and Mann-Kendall test.

Results 1) The multi-year-average rainfall erosivity of Henan province ranged from 1 696 to 6 106 MJ·mm/(hm²·h), showing a decreasing trend from southeast to northwest. The rainfall erosivity in spring, summer and winter also presented similar distribution characteristics, while the north-south differentiation of rainfall erosivity in autumn was more obvious. The high-high concentration areas of rainfall erosivity were mainly concentrated in the southern part of Henan province, with a high risk of rainfall erosion. 2) The annual and seasonal rainfall erosivity showed a significant concentration. Rainfall erosivity was mainly concentrated in summer, and there existed an increasing trend of summer rainfall erosivity in most years.

Conclusions Rainfall erosivity in Henan province was unevenly distributed within the year and fluctuated greatly, but the change was not significant. Tongbai-Dabie Mountain area, Loess Hilly Region of western Henan province, and Yellow River Flood area in eastern Henan province all had higher risk of rainfall erosion. The results can provide scientific basis for dynamic monitoring of soil erosion, soil and water conservation planning and soil erosion prevention in Henan province.