Variability and change of precipitation were investigated in Kumamoto on Kyushu Island in southwestern Japan, to assess water resources and flooding risk. Annual precipitation, annual maximum daily precipitation, and annual maximum hourly precipitation have increased over the period from 1891 to 2018 (128 years). Trends are 26.2 mm per decade, 6.07 mm/day per decade, and 2.17 mm/h/decade, respectively. Precipitation in the rainy season (June and July) is on average 37% (ranging from 12 to 59%) of annual precipitation for the 128-year period. Maximum daily precipitation in a year occurred at Kumamoto in the rainy season in 92/128 (72%) of the years of observation from 1891 to 2018, in the typhoon (August to November) season in 23/128 (18%), and in the March to May season in 12/128 (10%). This indicates that the rainy monsoon season poses the largest daily flooding risk. A wavelet analysis revealed that from 1891 to 2018 annual precipitation and daily maximum precipitation fluctuate with 2 and 4 years periods, which may be related to the El Nino-Southern Oscillation (ENSO). It is likely that air temperature rises, ENSO and topographical characteristics contributed to an increase in precipitation in the period. The analysis also showed that typhoons hitting or approaching Kumamoto have significantly affected annual precipitation and annual maximum daily precipitation, while the interval between typhoons affecting Kumamoto has been getting longer since the 1970s.

在日本西南部九州岛的熊本县调查了降水的变化和变化，以评估水资源和洪水风险。从1891年到2018年（128年），年降水量，年最大日降水量和年最大小时降水量有所增加。趋势分别是每十年26.2毫米，每十年607毫米/天和2.17毫米/小时/十年。在128年期间，雨季（六月和七月）的平均降水量为年降水量的37％（从12％到59％）。在1891年至2018年的观测年中，熊本在雨季的年度最大日降水量出现在92/128（72％）年，在台风（八月至十一月）的23/128（18％）年出现在3月至5月的12/128（10％）。这表明雨季季风带来了最大的每日洪水风险。小波分析表明，从1891年到2018年，年降水量和日最大降水量在2年和4年期间波动，这可能与厄尔尼诺-南方涛动（ENSO）有关。这段时期内，气温升高，ENSO和地形特征可能导致了降水增加。分析还表明，台风袭击或接近熊本已经极大地影响了年降水量和年最大日降水量，而自1970年代以来，影响熊本的台风之间的间隔时间越来越长。这可能与厄尔尼诺-南方涛动（ENSO）有关。这段时期内，气温升高，ENSO和地形特征可能导致了降水增加。分析还表明，台风袭击或接近熊本已经极大地影响了年降水量和年最大日降水量，而自1970年代以来，影响熊本的台风之间的间隔时间越来越长。这可能与厄尔尼诺-南方涛动（ENSO）有关。这段时期内，气温升高，ENSO和地形特征可能导致了降水增加。分析还表明，台风袭击或接近熊本已经极大地影响了年降水量和年最大日降水量，而自1970年代以来，影响熊本的台风之间的间隔时间越来越长。