The urban heat island effect (UHI) caused by the regional-to-global environmental changes, dramatic urbanization, and shifting in land-use compositions has becoming an important environmental issue in recent years. The strengthen of UHI effect significantly enhances the frequency of high temperature, and influences the thermal environment in urban area. In addition, the urban expansions due to dramatic increasing in urban populations and traffic loading significantly impacts the air quality in many metropolitan areas, especially in Asia.

In this study, the main objective is to quantify and characterize the temporal and spatial distributions of thermal environment in different cities in Taiwan, especially in the Greater Taipei Metropolitan Area by using monitoring data from Central Weather Bureau (CWB), and Environmental Protection Administration (EPA). In addition, in this study, we are going to conduct the analysis on the distribution of physiological equivalent temperature in the micro scale in the metropolitan area by using the observation data and the numerical model, RayMan, to investigate how the thermal environment is influenced under different conditions. According to the meteorological data from CWB frequency of high temperature (greater than 27 ° C) in the major metropolitan areas in Taiwan (Taipei, Taichung, and Kaohsiung) have increased in the past 50 years from 1960 to 2010. In this study, we characterize heat environment in the greater Taipei metropolitan area by using the meteorological data collected from CWB and EPA. In addition, we apply RayMan model to quantify the physiological equivalent temperature (PET) and characterize of the spatial and temporal distributions of the heat environment over different scales in the Taipei metropolitan area. The results can be integrated into the management and planning system, and provide sufficient and important background information for early warning systems for metropolitan area.