DRY FALLOUT OF SEA-SALT PARTICLES AND ITS SEASONAL AND DIURNAL VARIATION

Abstract

A dry fallout gauge is devised, which can determine dry fallout of the sea-salt particles, by the use of Farlow's halide-ion sensitive film, in the daytime as well as at night. The ten-day-average rate of dry fallout of sea-salt particles is determined in Kyoto for three years since November, 1962. The rate of fallout is high in winter, low in summer, and nearly the same feature is observed for three years. This seems to be caused by a larger supply of the particles from the Sea of Japan in the winter season. The total dry fallout of sea salt in Kyoto is found to be 1.7 x 10-^5 gm cm-^2 year-^1, and the average size distribution of the particles is determined. It is also found that there is a conspicuous diurnal variation in the rate of dry fallout : the value is several times larger at night than in the daytime. This is caused by diurnal variations in relative humidity and number concentration of the particles in the lowest atmosphere. The fact that the rate of dry fallout is only a small per cent of the total ground sink of seasalt particles is noticed, and a discussion is given.