Precipitation characteristics and large-scale atmospheric fields on the heavy rainfall days in the eastern part of Japan (Climatological features in midsummer and the supplemental study for the Baiu season)

Abstract

　Rainfall characteristics and large-scale atmospheric fields on the “heavy rainfall days” (with more than 50mm/day) in midsummer, and so on, at Tokyo in the eastern Japan were examined for 1971 to 2010, succeeding to Matsumoto et al. (2013) 　The present study firstly examined the rainfall features and the atmospheric fields for the “heavy rainfall days” at Tokyo with rather lower appearance frequency than in the typhoon related patterns in Matsumoto et al. (2013) and so on. In these cases (three cases in total), although the synoptic situations were rather different among each other, they seem to occur under the systems with relatively small zonal scale associated with the great meander of the upper-level westerly wind. 　Next, the climatological analyses similar to Matsumoto et al. (2013) were performed for the "heavy rain days" at Tokyo in midsummer (1~31 August). The precipitation on the “heavy rainfall days” at Tokyo in midsummer was mainly brought by the intense rainfall with more than 10 mm/h, as in the western Japan in the mature stage of the Baiu season. The detailed examination of the rainfall features for the case on 10 August 2009, with use of the 10-minutes precipitation data and the Radar AMeDAS Composite Data by the JMA, revealed that the organized meso-β-scale convective rainfall systems as often appear in the western Japan in the mature stage of the Baiu season were just to the east of the typhoon, and brought the intense rainfall at Tokyo to result in the large daily precipitation