SPATIOTEMPORAL DISTRIBUTION OF RAINFALL IN MOUNT SAKURAJIMA BASED ON WEATHER RADAR

Abstract

 Mount Sakurajima is one of the most active volcanoes in the world, where its frequent eruption causes the occurrence of debris flows every year. This paper discusses the fundamental aspect of spatial and temporal rainfall variability in Mt. Sakurajima by using X-band polarimetric (multi parameter) RAdar Information Network (XRAIN) related to debris flow occurrence. The analysis used XRAIN data from May 2015 to April 2016. The Meiyu-baiu rainfall phenomenon strongly affects the seasonal variability of rainfall in Mt. Sakurajima, which increases the precipitation in June to July. There are the possibilities of the beam blockage and the Vertical Profile Reflectivity problems to underestimate the XRAIN rainfall in Arimura and northern area of Sakurajima for a total of more than 1000 mm depth annually. However, there is no debris flow event reported in northern part during 2015 despite thicker accumulated volcanic ash, which may indicate that this area indeed receives less rain throughout a year. Most of the debris flows happen because of more than 9 hours long rainfall events, which validates the importance of rainfall on debris flow occurrence in Sakurajima.