Abstract
This paper examines the relationship between the warm season precipitation and the historical highest hourly and daily precipitations based on AMeDAS data during 25 years (1979-2003, 1088 observatories) for simple estimation method of heavy rainfall. The linear regression equation is obtained for the historical highest (25-year highest) precipitation and the warm season precipitation from April to October, which indicates highest correlation. The equation is used for mapping of 25 year precipitation estimates. The equation is also used to define the “heavy rainfall blank areas” in which some AMeDAS observatories have the historical highest precipitation smaller than one estimated by the equation. Defined “heavy rainfall blank areas” are especially Akita, Toyama, Ishikawa and Fukui prefectures and the neighborhood. This result is similar to our past research based on the data from 1979 to 1998. In future, there is a possibility of occurrence of heavy rainfall over past 25-year record in these areas. Actually, heavy rainfall events occurred on Niigata and Fukui prefectures in 2004. These areas were “heavy rainfall blank area” though the present precipitation amounts at several observatories were exceeded the estimated 25-year highest precipitation amounts.
