The Ohzu Basin is located in the north western part of Shikoku Island as is shown in Fig. I. As in other basins in Japan, basin fog appears frequently from autumn to winter. In order to make clear the climatological characteristics of basin fog at the Ohzu Basin, Ehime prefecture, and understand its role as an element of agro-climatological resources, observations were carried out from Sep. 8, 1995 to Feb. 5, 1996. The sites were located at bottom of the basin and on mountainside faced to the center of the basin. The latter site was situated above the upper surface of the fog layer which appears typically in the Ohzu Basin. Spatial distribution of the fog were also analyzed using the LANDSAT images provided on Dec. 5, 1985 and Dec. 13, 1988. The results obtained in this study were summarized as follows: (1) The total number of fog day reached 46 days during the present observation period mentioned above. In the most frequent period, fog occurred at the ratio of one day to two day in October and November. (2) Dispersion time of the fog changed seasonally accordance with a shift of time of sunrise, and the fog has lasted 4 hours or more after the sunrise under dominant foggy conditions. (3) The meteorological characteristics of foggy day were shown as follow, attenuated of solar radiation in the morning, decreased of radiative cooling in nighttime, and low temperature until fog dissipate. (4) Several percent of monthly total solar radiation was shaded by fog layer at the basin bottom site. Total time of saturation condition indicated by R.H.= 100 percent on foggy days became 21 hours at the site of mountain slope. At the basin bottom site, it reached 493 hours during the period of the observation. (5) Upper surface of the fog layer was limited to a height about 300 m above the sea level, and distributed horizontally along lower part of the Hiji River. The maximum height was affected by the surrounding topography. (6) In the Ohzu Basin, hamlets on the mountain slope distributed zonally above the fog layer. This indicates that the fog has a remarkable influence on human life of mountainous region. On the other hand, the chinese cabbage-producing district was formed in the foggy area. Utilizing this foggy climate of the basin, high quality chinese cabbage with soft leave are produced in the basin bottom.
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