Comparison of outdoor thermal indices in urban parks: which index is most “accurate”?

Authors: Winston Chow*, National University of Singapore, Aikeen Lim, National University of Singapore
Topics: Climatology and Meteorology, Asia
Keywords: Climate
Session Type: Poster
Day: 4/4/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: Download



Consideration of outdoor thermal comfort in urban areas is gaining prominence within geographical research. This is true in rapidly-expanding low-latitude cities where information about personal exposure to microclimates in cities is important to urban stakeholders in mitigating excess urban heat/thermal discomfort. A question remains if estimates of thermal comfort – e.g. through empirical (i.e. derived from climate variables only) or rational (i.e. accounting for human body-climate energy balance interactions) approaches are comparable in accuracy, especially when gauged against sensation votes from surveyed data. To this end, this study investigates the impacts of microclimatic parameters on thermal comfort within two large tropical urban parks, and how quantification of measured (objective) thermal comfort relates to perceived (subjective) thermal comfort. Field measurements were conducted over ten days in two popular urban parks in Singapore using heat stress instruments, which were subsequently used to derive several thermal comfort indices e.g. wet-bulb globe temperature (WBGT), physiological equivalent temperature (PET) and modified physiological equivalent temperature (mPET). Additionally, a total of 1942 park users were also surveyed during fieldwork days to obtain perceptions of the ambient thermal environment. We attempt to ascertain if significant differences exist within, and between the indices with surveyed perception data. Initial results indicate that indices were most significantly influenced by air temperature, followed by mean radiant temperature, relative humidity, and wind velocity; that significant differences in accuracy exist between empirical and rational heat indices; and that notable disparities are apparent between measured thermal indices and subjective thermal comfort across parks.

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