Applicability of Heat Index for Effective Heatwave Response

Abstract

Damage caused by heatwaves has been increasing recently worldwide. As climate change led by global warming progresses, heatwaves are projected to cause the most damage. Thus, it is very important to issue an appropriate heatwave advisory so that one can be prepared for it. Considering that the degree of heat experienced by people differs depending on the difference in humidity between regions with similar summer temperatures, it is necessary to evaluate whether the issuance of a heatwave warning using only the daily maximum temperature is appropriate. This study intends to examine the applicability of the heat index considering both temperature and humidity for effective heatwave response. First, the agreement between the occurrences of heatwaves and heat-related illness, where the occurrence is decided by the daily maximum temperature and daily maximum heat index, was evaluated. The results show that when the daily maximum heat index was applied as a criterion for issuing a heatwave warning, the coincidence with the occurrence of heat-related illness was more than two times higher than when the daily maximum temperature was applied. Next, on evaluating the prediction accuracy of the heat index according to the prediction-related leading time, the accuracy of the heat index was noted to be higher than that of the temperature for all the leading times; the highest accuracy was shown at the leading time of 10 hours (NSE = 0.7196; CORR = 0.8698). Based on the results of this study, it is necessary to consider using a heat index that contains both temperature and humidity elements to issue a heatwave warning. Furthermore, to establish regional standards for heatwave warnings, the relationship between heatwave characteristics and meteorological factors should be first analyzed using long-term data from various observation points.