Seasonal Variations in Fog and Temperature Changes in the Fukuchiyama Basin, Kyoto Prefecture

Abstract

This study investigated the seasonal variations in the number of foggy days and the associated temperatures during fog events in the Fukuchiyama Basin. During the 119 days observation period, fog occurred on 31 days (26%), with the highest occurrence frequency in November, accounting for 50% of the total. Meanwhile, the dissipation time of fog strongly depended on sunrise time and subsequent solar radiation. A difference of approximately 3 hours was observed between December, around the winter solstice, and March in spring. Furthermore, at the observation site located at the bottom of the basin, an increase in temperature was observed immediately after fog formation, in contrast to the temperature decrease due to radiative cooling during the night. This phenomenon, observed on 55% of foggy days, is attributed to downward longwave radiation emitted by fog particles reaching the earth’s surface.