2010年8月上旬のラダーク鉄砲水災害時の降水・気象条件

Abstract

Ladakh, located in northern India, experienced flash flooding and debris flow from 4–7 August, 2010. The Research Institute for Humanity and Nature's high-altitude project installed an automatic weather station (AWS) and small temperature and humidity sensors in Ladakh in June, 2009. These instruments recorded the meteorological conditions associated with the unprecedented disaster in Ladakh. This study presents meteorological data recorded from late July to early August, 2010, compares these data with data recorded during two other years (2009 and 2011), and investigates linkages between the data recorded in August, 2010 and the large-scale circulation field. Flooding occurred in Ladakh during the nights of 4–7 August, when the rainfall was most concentrated. Recorded AWS pressure and wind data reveal a clear diurnal circulation, suggesting a plateau-scale diurnal variation. From 4–7 August, 2010, southerly and easterly winds prevailed and surface air pressure was higher than during the other two years. These changes corresponded to easterly winds turning around the south of the Tibetan High located in the northern part of the Tibetan Plateau. Moisture came into Ladakh from the south part of the Plateau. The timing of the precipitation event in Ladakh differed from that of the moisture/ precipitation surge in the northern part of Pakistan. When Pakistan experienced precipitation events in late July, most stations in Ladakh recorded relatively high humidity during this time, but Ladakh experienced no precipitation in July except for 1 mm on 28 July at Leh. The moisture flow pattern associated with the flooding in Ladakh differed from that associated with the flooding in Pakistan, but during the boreal summer of 2010 the heat wave in Russia, the flooding in Pakistan, and the flooding in Ladakh were all related to the wave energy transport of the jet stream.