Reply on RC3

Abstract

Severe water erosion occurs during extreme storm events. Such an extreme storm occurred in Zhengzhou in central China on 20 July 2021 (the “7.20” rainstorm). The magnitude and frequency of occurrence of this storm event were examined in terms of its erosivity values. To contextualize this extreme event, hourly rainfall data from 2420 automatic meteorological stations in China from 1951 to 2021 were analyzed to: (1) characterize the spatial and temporal distribution of rainfall and rainfall erosivity of the “7.20” rainstorm, (2) evaluate the average recurrence interval of the maximum daily and event rainfall erosivity, and (3) establish the geographical distribution of the maximum daily and event rainfall erosivity in China. The center of the “7.20” rainstorm moved from southeast to northwest in Henan province, and the most intense period of rainfall occurred in the middle and late stages of the storm. Zhengzhou meteorological station happened to be aligned with the center of the storm, with a maximum daily rainfall of 552.5 mm and a maximum hourly rainfall intensity of 201.9 mm"∙" h-1. The average recurrence interval of the maximum daily rainfall erosivity (43,354 MJ·mm·ha-1· h-1) and the maximum event rainfall erosivity (58 874 MJ·mm·ha-1·h-1) was estimated to be 109 079 and 154 154 years, respectively, assuming the generalized extreme value distribution, and these were the maximum rainfall erosivity ever recorded among 2420 meteorological stations in mainland China. The “7.20” rainstorm suggests that the most erosive of storms does not necessarily occur in the wettest places in southern China, and it can occur in mid-latitude around 35 °N with a moderate mean annual precipitation of 549.2 mm in Zhengzhou meteorological station.