Spatial-temporal evolution and driving forces of rainfall erosivity in a climatic transitional zone: A case in Huaihe River Basin, eastern China

Rainfall erosivity (R-factor) is a crucial natural factor in assessing soil loss by water erosion. Understanding the spatial-temporal variation of R-factor and its driving forces is essential to reduce soil and water loss as well as formulate a regional ecological restoration plan. In this study, the Huaihe River Basin (HRB), a typical climatic transitional zone of eastern China, was selected as the study region. Using daily precipitation data of 36 national standard meteorological stations in the HRB during 1960-2014, the temporal variation and spatial pattern of Rfactor were examined. To explore the influence of large-scale atmospheric circulations, three climatic indicators - the tropical Pacific sea surface temperature (SST), the East Asian summer monsoon (EASM), and the Arctic Oscillation (AO) - were analyzed with R-factor by the cross-wavelet transform. Results indicated that: (1) Average annual R-factor was 5339.64 MJ.mm.hm(-2).h(-1) with an insignificantly increasing trend. Summer accounted the most of seasonal R-factor, followed by autumn and spring. Only the winter R-factor presented a significantly increasing trend. (2) The spatial gradient of R-factor decreased from south to north in the HRB. The common high value of R-factor appeared in the Dabie Mountain. In summer, another high value of R-factor mainly concentrated in the coastal of HRB. (3) Climatic indicators had a strong influence on R-factor in this region. The non-stationary feature was reflected by the resonant period between R-factor and climatic indicators. It should be noticed that the winter R-factor is increasing when the positive phase of AO in the long-term period. This study is helpful to understand the variation of rainfall erosivity in the climatic transitional zone of eastern China.