Distribution of Rrecipitation during the Short Dry Period of Mid-Summer in Fukushima Prefecture and Northern Kanto Area

Abstract

It is said that Japan has a short dry period in mid-summer. However even in such a period, the local rainfall is frequent in some regions. The author clarifies the distribution of such a local rainfall during the short dry period, using data for precipitation in Fukushima Prefecture and Northern Kanto area (Fig. 1).The results are summarized as follows;1) The local rainfall in mid-summer is often observed along the north borders of Tochigi Prefecture. This area does not always coincide with the region abundant in total summer precipitation (Fig. 3).2) As a whole, the local rainfall in mid-summer occurs during 1600-1800 JST, and it tends to stop within two hours (Table 1), but each station has a different characteristic in hourly occurrence (Fig. 4). In the northwestern Tochigi Prefecture, the local rainfall in mid-summer inclines to occur in the earliest time (Fig. 5 and Fig. 7).3) The ratio (%) of amount of precipitation in the dry period of mid-summer to that of total summer precipitation is highest, about 20%, in Yamizo Mountains, Tadami area, and around Kiryu (Fig. 9). The ratios fluctuate considerably year-to-year, and in some case, they exceed 50%.