霜害発生予察のための５０ｍメッシュ地形情報を用いた局地的冷却現象の解析

Abstract

Localized cooling Index (LCI) was calculated from temperature data measured at night during the Spring period at the agricultural farm and the AMeDAS station in Yamaguchi Prefecture.On clear nights, relatively lower cooling degrees than usual were obtained in the inland basins and significant differences for localized cooling were observed among different regions. On the contrary, on rainy nights, lower cooling degrees than the standard were found in the coast and inland hills. From evening to midnight, localized cooling varied with time among different regions, however, from midnight to morning tendency of variations for localized cooling did not much change. Therefore, if a low temperature could be estimated using LCI at 2300, this result would provide useful information for the prediction of late frost occurrence.Effect of topography on localized cooling differs from place to place. For inland areas, localized cooling mostly developed in complex terrain and behind the northwest mountains. In the west and east, localized cooling developed in the places behind the western and southwestern mountains, respectively. This phenomenon may be attributed to the fact that general wind was intercepted by the mountain and localized cooling developed.The mean LCI at 2300 in April was estimated using multiple-regression analysis. The adjusted R square (R2′) varied from 0.63 to 0.94. Therefore, it may be possible to use a multiple-regression formula for the quantitative estimation of localized cooling phenomenon.