NUMERICAL PREDICTION OF OUTDOOR THERMAL INDEX USING MESOSCALE METEOROLOGICAL MODEL

Abstract

This study demonstrates the numerical prediction of thermal sensation index for outdoor environment (SET*OUT) using Regional Atmospheric Modeling System (RAMS). SET*OUT, one of the major thermal sensation index, requires data sets of wind velocity, absolute humidity, air temperature and each component of short wave and long wave radiation in both upward and downward directions. Temporal and spatial variation of SET*OUT over the Kanto Region on August 10 1998 has been presented and discussed. The thermal sensation index for indoor environment (SET*IN) is referred to as a comparison. It is found that the variation of SET*OUT is strongly influenced by mean radiation temperature and sea breeze penetration. The mean radiation temperature, and consequently SET*OUT, have distinctive double peaks in the morning and the afternoon due to the shape factor of cylindrical human body for direct solar radiation. The first peak of SET*OUT in the morning roughly corresponds to the arrival of sea breeze front, and the value is generally larger than that of the second peak in the afternoon. Such a behavior of SET*OUT can be accounted for by the fact that the sea breeze increases wind velocity and activate the heat transfer from human body. SET*IN is similar to but slightly (0.5-1°C) larger than air temperature, which is due to the high humidity condition in Tokyo area.