Local Meteorological Characteristics at Takase Basin, Kagawa Prefecture on fine days in Winter Season
1990 Volume 46 Issue 2 Pages 79-86
Details
1990 Volume 46 Issue 2 Pages 79-86
The local meteorological observation was carried out at Takase Basin and the south west slope of Osa Mountain, Kagawa Prefecture on clear-fine day in winter, Jan. 19-21, 1988.
The cold air lake was observed at the bottom of Takase Basin and the thermal belt observed at the slopes of 100-500m of Osa Mountain and 100-200m of Asahi Mountain. The vertical differences of both air and surface temperatures for the typical inversion layer were 6-7°C and about 10°C, respectively, and the thickness of the inversion layer was 80-100m at the basin bottom. In the case of small cold air current, the cooling seemed to be larger, because the air current was easy to stand on the gentle slope. The pan-type distribution of isotherm was recognized at the basin.
The change of wind direction and the frequency of weak wind of 1m/s were higher at the basin bottom. The cold air current of 1 to 3m/s was observed at the slope and its wind speed was relatively heigher at the lower region of the slope. The cold air current seemed to blow from the elevation of about 400m. The stronger the wind speed of the air current was, the higher the air temperature was at the foot of the mountain, however, the air temperature seemed to be constant in the case of wind speed over 3m/s.
The relative humidity and the appearance frequencies of dew and frost were higher at the basin bottom, but lower at the slope and the foot of the mountain in the case of cold air current. The air was dry and its temperature was high at the observation base of 160m in the blowing period of cold air current. The amounts of dew and frost were few, and the latent heat flux by evapotranspiration was occasionally released from the soil surface even at night. As the cold air current blowing from the thermal belt is the warmer wind at the slope and supplies the sensible heat to the crop at the foot of the mountain, its utility is high as meteorological resources along with the thermal belt.
