Abstract
Abstract. On August 20 of 2014, Hiroshima City (Japan) was struck by local heavy rain from an autumnal rain front. The resultant debris flow disaster claimed 75 victims and destroyed many buildings. From 1:30 am to 4:30 am on August 20, the accumulated rainfall in Hiroshima City exceeded 200 mm. Serious damage occurred in the Asakita and Asaminami wards of Hiroshima City. As a disaster prevention measure, local heavy rain (localized torrential rains) is usually observed by the Automated Meteorological Data Acquisition System (AMeDAS) operated by the Japan Meteorological Agency (JMA) and by the C-band radar operated by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, with spatial resolutions of 2.5 km and 1 km, respectively. The new X-band MP radar system enables more detailed rainfall observations than the C-band radar. In fact, this radar can observe local rainfall throughout Japan in near-real time over a minimum mesh size of 250 m. A fine-scale accumulated rainfall monitoring system is crucial for disaster prevention, and potential disasters can be alerted by the hazard levels of the accumulated rainfall.
Highlights
As warm wet air flowed toward a stationary front that had stagnated in the Sea of Japan, the atmosphere above Hiroshima Prefecture destabilized, dumping severe rain around Hiroshima City from the night of August 19 to the dawn of August 20, 2014
To prevent rain-related disasters, localized heavy rain in Japan is usually observed by the Automated Meteorological Data Acquisition System (AMeDAS) operated by the Japan Meteorological Agency (JMA) and by the C-band radar operated by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, with spatial resolutions of 2.5 km and 1 km, respectively
JMA provides a standard for the rain situation, which shows the hazard levels of hourly rainfall amounts
Summary
As warm wet air flowed toward a stationary front that had stagnated in the Sea of Japan, the atmosphere above Hiroshima Prefecture destabilized, dumping severe rain around Hiroshima City from the night of August 19 to the dawn of August 20, 2014. The August 20, 2014, sediment disaster was the most severe in Japan throughout the past 30 years, resulting in 74 deaths This damage exceeded even the large-scale landslide disaster that struck Hiroshima City on June 29, 1999 (the socalled disaster by June 29 downpours). The spatial resolutions of AMeDAS and Cband radar (which recorded the Hiroshima City downpour on August 19-20, 2014) are inadequate for precise rainfall measurements. Using the rainfall data of the MLIT Xband MP radar for Asakita and Asaminami wards in Hiroshima City, which experienced a large-scale sediment disaster (landslide), this study analyzes the outline and features of the August 2014 downpour. This chain of heavy rains has been called "Downpour in August 2014" by the Meteorological Agency
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