Analysis of long-term changes in precipitation over central Japan by utilizing daily precipitation series from Kunai, the former local observation network

Before the current local observation network of the Japan Meteorological Agency (JMA), i.e., Automated Meteorological Data Acquisition System (AMeDAS), the former local observation network, i.e., Kunai, was used. Data sets from Kunai observation network were utilized to obtain homogeneous high spatial density daily precipitation data over central Japan, from 1931 to 2021. This enabled us to use data from 106 stations to analyze, in detail, the regional variability and trends in precipitation. The results showed an overall increasing trend in the frequency of heavy rainfall and a decreasing trend in that of moderate rainfall; however, sub-regional and seasonal differences were observed.