九州南部における4月頃の大雨日の降水の特徴と 大気場に関する総観気候学的解析

Around April, total precipitation in southern Kyushu already attains rather large value due to the increase in contribution of the “heavy rainfall days” (with daily precipitation more the 50 mm/day, referred to as HRD). The present study examined the rainfall features and atmospheric conditions on the HRDs at Kagoshima in southern Kyushu, based on the operational observation data from 1990 to 2009. The HRDs there in April appeared mainly associated with the extratropical cyclone passage, together with tentative appearance of the stationary front. The mean daily precipitation on the HRDs was 82 mm and contribution of the intense rainfall more than 10 mm/h attained up to 38 mm, which accounted for 46 % of the daily total precipitation. In April, the high specific humidity area in the time mean field was still located far to the south of the Japan Islands and the stratification around the Japan Islands was very stable for deep moist convection. However, the zone with rather strong seasonal mean baroclinicity extended to rather southern area near 20°N. This would provide a favorable condition for the long-distance moistur