Analysis on the Thermal Belt on the Mountain Slope using LANDSAT Images and a Digital Terrain Model

Abstract

The thermal belt is observed on two LANDSAT thermal images over and around the Kanto Plain, central Japan. The thermal belt is not a local phenomenon, but it extends over a large area at least several hundred kilometers. It can be obviously recognized in an image taken on 27/JAN./1987, but it is not in an image taken on 25/FEB./1986. The synoptic condition at each observation time may cause the difference in the extent of the thermal belt. In this paper, we report on the results of our investigation for the thermal belt using LANDSAT thematic mapper band 6 images and a digital terrain model.
A LANDSAT thermal band image taken in 1987 was geometrically corrected to the latitude-longitude coordinate. Air temperatures at 68 mete-orological observation stations (AMeDAS) were compared with surface temperatures derived from LANDSAT CCT counts at the corresponding points. The equation to estimate air temperature at any pixel can be obtained with the correlation coefficient of 0.833.
A LANDSAT thermal image in 1987 was super-imposed to a digital terrain model (KS110 in Digital National Land Information by the Geographic Survey Institute). Air temperatures on mountain slope show strong inversion. The top of the inversion layer is about 100 to 200m above the piedmont. Aerological observation data at Tateno Meteoro-logical Observatory at the time of LANDSAT-5 overpass show strong inversion of air temperature below 154m above the ground.This hight corresponds to the relative hight of the inversion at a mountain slope. Therefore the radiative cooling is closely related to the formation of thermal belt on a mountain slope.
The distribution of wind direction and wind speed on 25, February 1986 implies that adiabatic warming of air blowing down the mountain slope may form the stable layer. Therefore the formation of the thermal belt is also connected with the wind as well as the atmospheric stability.