Predicting outdoor thermal sensation from two field studies in Curitiba, Brazil and Glasgow, UK using the Universal Thermal Climate Index (UTCI)

We present a comparative analysis of outdoor human thermal sensation against predictions with the Universal Thermal Climate Index (UTCI) for two sets of data collected in Curitiba, Brazil (subtropical climate in elevation) and in Glasgow, UK (maritime temperate climate). Surveys took place during daytime in pedestrian areas with microclimate measurements and concurrent administration of thermal sensation and preference questionnaires. Comparisons were made with regard to clothing levels (predicted by UTCIs clothing model versus actual garments observed) and votes of thermal sensation in relation to ambient temperature variations and to UTCI values. Results suggest that clothing levels are fairly well predicted by UTCIs clothing model for both cases. A small offset was noticed for Glasgow from the onset of the summer period, with UTCI overestimating actual clothing. More noticeable however were differences between clothing levels for Curitiba and Glasgow for the same ambient temperature range (roughly 15-20°C), which is also reflected on the thermal sensation votes for both locations. As those divergences are found for the start of the summer period in Glasgow, it is suggested that people under those climatic conditions accept lower air temperatures and indeed regard those as comfortable presumably due to acclimatization. For calculated UTCI, similar discrepancies have been observed for both cases, with a slight overestimation of actual thermal sensation for Curitiba and a slight underestimation of actual thermal sensation for Glasgow.