Temporal Variation in the Intensity of Convective Heavy Rainfall and Regionality in the Afternoon on Summer Days with Long Sunshine Duration in the Kanto District, Japan

Abstract

This study analyzed the regional characteristics of temporal variation in the intensity of convective heavy rainfall in the afternoon on summer days with long sunshine duration in the Kanto district. The data used for this study were the 10-min values recorded at AMeDAS observation sites in July and August between 2010 and 2020. The percentage of occurrence frequency of rainfall intensity categories 60 minutes before and after the maximum rainfall intensity (≥3.5 mm/10 min) helped identify four distinct types of temporal variations in the intensity of convective heavy rainfall events. Type I involved slightly more short-duration events and occurred extensively in the plains. Type II events had a slightly longer duration and occurred in the mountains of northern Kanto. Type III was a short period from the beginning of rainfall occurrence to maximum rainfall intensity and distributed near the foot of mountains or on the plains. Type IV was distributed in the southeastern part of the study area, and had a long duration and weak rainfall intensity 60 minutes before and after the maximum intensity. These regional characteristics are related to the spatial scale, occurrence, development, and passage of rainfall.