Background  Rainfall erosivity (R-factor) reflects the potential of soil erosion caused by rainfall. It is of great practical significance to study the temporal and spatial distribution characteristics of R-factor. Shanxi is one of the most serious soil erosion provinces in China. In order to reveal the influencing factors of soil erosion and their contribution rates in Shanxi, it is necessary to study the R-factor in the province. There are many R-factor estimation models at home and abroad, among which the semi-monthly model proposed by Chinese scholar ZHANG Wenbo is widely used.

Methods  Based on the daily rainfall data of 109 weather stations in Shanxi province from 2000 to 2016, this paper estimated the R-factor by using the mentioned semi-monthly model and co-Kriging interpolation method. Then it analyzed the temporal and spatial distribution characteristics of R-factor.

Results  There were about 12 erosive rainfalls per year in Shanxi, with an average rainfall of 24.59 mm. The average annual erosive rainfall (P_y12) of 109 weather stations was significantly correlated with the average annual erosive rainfall (P). The relationship between the two was expressed by P_y12=0.80P-96.86. The R-factor in the study area was from 663.05 to 2 810.32 MJ·mm/(hm²·h·a) with an average of 1 628.71 MJ·mm/(hm²·h·a). Moreover, the R-factor in the three-quarters of the study area was 1 200-2 000 MJ·mm/(hm²·h·a). In terms of spatial distribution, the R-factor generally showed an increasing trend from northwest to southeast. To be specific, the Southeastern region had the highest R-factor followed by the Southern region, the Middle region again, and the Northern region with the lowest. In terms of temporal distribution, the R-factor was unevenly distributed within the year, showing a trend of first rising and then decreasing, and the highest value usually appeared in the second half of July. Affected by the monsoon climate, more than 90% of annual rainfall erosivity was concentrated in the warm season (from May to September).

Conclusions  The frequency of erosive rainfall in Shanxi province is relatively high. The R-factor is significantly correlated with annual average rainfall (P) and annual average erosive rainfall (P_y12), which are estimated by R=0.006 8P^1.99 and R=0.34P_y12^1.48 respectively. Most of erosive rainfall occur from July to September, thus this period is particularly critical for soil erosion prevention and control in the entire province.