Future change in the spatial distribution of the thermal.

  • Shiori Abe, 2012: Future change in the spatial distribution of the thermal. .


Recently, summertime temperature and total number of uncomfortable nights have been increased due to global warming (GW) and urban heat island (UHI). Therefore, the health hazards such as heatstroke and sleep disorder are currently concerned. Associated with future global warming,regional climate in Japan will be changed.  This study evaluates the risk of human health by drawing the climatological distribution of thermal indices. Here, Discomfort Index (DI), Wet-bulb Globe Temperature (WBGT), and Wind Chill Index (WCI) are used as thermal index. In addition, the future changes of the risk of human health are evaluated, using a regional climate model WRF (Weather Research and Forecasting).

  In summer, DI, broadly indicates “uncomkfortable condition”in the daytime.This “uncomfortable” environment is reduced slightly in the nighttime. In the big cities, however, the “uncomfortable” environment is continued during the nighttime as well as daytime. This result would be due to the UHI.

The observations show that the maximum daily WBGT is not in good agreement with the total hours of WBGT having more than 28 degrees. This result indicates that the continuous risk of heatstroke is not in good agreement with the momentary risk of that. In winter, the risk of chilblains exists in Hokkaido and Tohoku district from the limatological distribution of WCI.

Compared between current and future climate using WRF, the average WBGT increased with progression of global warming. In addition, the total hours of WBGT having more than 28 degrees increased largely. Thus, the risk of heatstroke increased in the future. This trend is predominant in Hokkaido and Tohoku districts. Associated with progression of global warming, the numbers of the extreme hot days and the tropical nights are increased. On the other hand,the number of frost days and the ice days tends to decrease in the future. But,there is almost no variation in the climatological distribution of WCI in the future.

  To discuss about human health, weather factors such as air temperature and relative humidity is insufficient. Hence, it would be necessary to use the thermal index like WBGT.

Key words:  human health, Wet-Bulb Globe Temperature,Discomfort Index, Wind Chill Index, global warming