ANALYSIS ON DIURNAL VARIATIONS OF HEAVY RAINFALL FEATURES IN KYUSHU, JAPAN, USING SELF-ORGANIZING MAP

Abstract

 The first aim of this study is to investigate the features of diurnal variations in heavy rainfall frequency, and to relate them to typical meteorological fields during a warm season in Kyushu, Japan, using Self-Organizing Map (SOM). The result showed a tendency of higher heavy rainfall frequency in the morning compared with in the afternoon. The meteorological field patterns are characterized by the inflow of warm and humid air into frontal area. The second aim of this study is to clarify significant relationships between heavy rainfall hours of the day and disasters cases which occurred in Kyushu during 2006 and 2020 using the first and second maxima of heavy rainfall scale and hourly rainfall recorded in each hour. One of the trends is characterized by widespread and local heavy rainfall in the morning including sleeping time and in the daytime, respectively. Actually, the time-dependent features are true of disaster cases including 2017 and 2020 disaster cases in Kyushu. Therefore, the findings provide strong evidence for night-time disaster prevention in Kyushu.