降下ばいじん量と降水量の間の関係について(第3報)

Abstract

This paper treats the data of dust-fall and rain-water caught simultaneously by depositgauges in Kasugai and Ohtake cities during the fiscal year 1984; the data of Kasugai city and the coastal area of Mikawa bay for the fiscal years 1982 and 1983 have been reported in two foregoing papers, and after these, we have likewise examined the present data. The results obtained are : (1) There holds an annual formula M/V=k・1/V+Δ between M (dust-fall, t/(km)^2・mo) and V (rain-water, L/mo) at a monitoring site, k and Δ being constants. (2) Expressing more fully, an almost linear relation M=m+αV-βV^2 applies, where m represents a constant independent of rain and α as well as β constants relating to the dust-particle collection efficiency of a rain-drop. (3) The efficiencies estimated under such meteorological conditions as rain-fall intensity 0.1～1.0mm/h and rain-drop diameter 0.5～1.0 mm are of the order of (10)^<-2>, this finding being just the same as that already reported. (4) The amount of suspending dust, a portion of which might be scavenged by rain is, by calculation, 3.3 and 3.7t/(km)^2・mo for Kasugai and Otake respectively.