Abstract
Using LANDSAT data with 250-m grid size, the characteristics of the thermal belt over mountainous regions were investigated under conditions of nocturnal radiative cooling in the winter season. The LANDSAT data were taken on Dec. 7, 1984 and Dec. 5, 1989. The scenes covered the west part of Shikoku, southwest of Japan.
Results were summarized as follows:
The thermal belts appeared between 400m to 1000m above sea level. The altitudes of the thermal belts were remarkably dependent on characteristics of the regional topography.
Altitude of the thermal belt was influenced by bottom-altitude of region. In the upstream region, the thermal belt appeared at high level over the slope. On the other hand, in the downstream region, that appeared at low level.
There was good correlation between depth of basin and thickness of inversion layer in the basin. The thickness of inversion layer increases up to 98m with the increment of the depth of basin of 100m height. That is, the thermal belt appeared at high level in the basin which had enclosed by high mountain.
When the altitude of the thermal belt was high level, the air temperature of the thermal belt was low. The air temperature of the thermal belt changes with a ratio of 1°C/100m. This temperature lapse rate was almost equal to the air temperature lapse rate shown by equation (1).
The meteorological resource of the thermal belt is decided besically by altitude of the thermal belt.
