Response of Spatial and Temporal Patterns of Water Erosion Dynamic Factors to the Main Atmospheric and Oceanic Circulation Patterns in the Chinese Mollisol Region During 1960—2020

[Objective] A study on the spatial and temporal patterns of water erosion dynamic factors and their responses to atmospheric and oceanic circulation patterns in the Mollisol region of Northeast China is crucial for preventing and controlling soil erosion in the context of frequent extreme precipitation events. [Methods] Four water erosion dynamic factors, including rainfall erosivity (R), heavy rainfall (R50p), very wet day precipitation (R95p) and the maximum five-day rainfall (R5d), were selected to characterize water erosion dynamic factors. Based on daily rainfall data from 1960 to 2020, the spatial and temporal patterns of the water erosion dynamic factors in the Chinese Mollisol region in 1960—2020 were analyzed using the moving average, wavelet analysis, Sen's method and Mann-Kendall test methods, and the responses of water erosion dynamic factors to atmospheric and ocean circulation patterns were analyzed. [Results] (1) The annual rainfall erosivity R varied from 1 145.36 to 3 575.94 (MJ·mm)/(hm2·h·a), heavy rainfall amount R50p was between 73.17 and 197.86 mm, very wet day precipitation R95p varied from 265.81 to 566.35 mm, and maximum five-day rainfall R5d varied from 69.67 to 124.95 mm in the Chinese Mollisol region from 1960 to 2000. (2) These water erosion dynamic factors in the study region did not show a significantly increasing trend over the past 61 years and did not show an overall abrupt change, but a noticeable upward trend was observed after 2015, which hinted that potential risk of rainfall erosion could rise in the near future. Moreover, the water erosion dynamic factors displayed periodic changes with a main cycle of approximately 44 years and a secondary cycle of 29 years, and they went through two oscillatory processes with high and low levels. (3) The spatial distributions of these water erosion dynamic factors showed high values in the south and central parts, and low values in the north, east and west parts. The maximum values occurred in the Changbai-Wanda hilly area, while the minimum values were in the Hulunbeier hilly plain area. (4) In addition, the East Asian Summer Monsoon Index (EASMI) was the most important single circulation pattern affected the water erosion dynamic factors, while the Arctic Oscillation (AO) and Multivariate ENSO Index (MEI) could indirectly affect the water erosion dynamic factors in the Chinese Mollisol region by influencing the East Asian summer monsoon. The superposition of the East Asian Summer Monsoon Index and the South China Sea Monsoon Index (EASMI-SCSSMI) had the most significant impact on water erosion dynamic factors (ΔPSAC>5%), while three circulation patterns of the East Asian Summer Monsoon Index, the South China Sea Monsoon Index and the Multivariate ENSO Index only significantly affected rainfall erosivity R (ΔPSAC>5%). [Conclusion] The factors that influence the spatial and temporal patterns of water erosion dynamics in the mollisol region of northeast China included topography, East Asian summer monsoon and South Asian summer monsoon, etc. Additionally, it is essential to be aware of the potential water erosion that may occur due to the rebound of water erosion dynamics after 2014.