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Ben Gurion University (2010)

The relation between urban microclimate and subjective thermal sensation in an arid region

Dixin Jiao

Titre : The relation between urban microclimate and subjective thermal sensation in an arid region

Auteur : Dixin Jiao

Université de soutenance : Ben Gurion University

Grade : Master of Science 2010

Résumé
Understanding outdoor thermal comfort can have major implications for urban design, and a number of comfort indices have been developed which account for the thermal interaction between the human body and its surroundings. However, the perception of thermal comfort depends on a host of factors beyond the physical conditions of the environment – and when indices of physical thermal stress have been compared with people’s actual thermal sensation, the correlations have most often been made under controlled indoor conditions. This research aims to clarify the relation between outdoor physiological thermal stress and subjective thermal sensation in the context of a desert climate, by comparing the results of climatic and perceptual surveys in a series of urban spaces with different geometry. Climatic measurements serve as input for calculating the Index of Thermal Stress (ITS), while the Physiological Equivalent Temperature (PET) is also employed as a comparative index. Questionnaires, distributed to pedestrians simultaneously with the measurements, are used to investigate human responses to varying thermal stimuli. The values of ITS and PET are then compared with subjective thermal sensation, to examine the relationship of perceived comfort with these physical indices. The relationship with ITS is further examined to quantify the extent to which personal variables account for variance in the basic correlation. Results of the microclimatic measurements largely reinforce findings of previous modeling studies, showing the dramatic effects of urban geometry on thermal stress in a hot-arid environment. The observed correlation between physiological thermal stress and perceived thermal sensation suggests that the thermal indices can predict pedestrians’ thermal sensation under real outdoor conditions to a fairly high degree (R2=0.56 for ITS, and slightly less for PET). The observed correlations indicate that pedestrians have a higher tolerance for increasing levels of thermal stress under varying outdoor conditions than under stable indoor conditions, but that the value of ITS which expresses fundamental thermal “neutrality” is relatively insensitive to the context. The analyzed non-environmental variables, when taken together with basic environmental stress as expressed by ITS, were found to explain a significant portion (approximately 70%) of the variance in reported thermal sensation.

Mots Clés : Arid regions climate — Israel. - City planning — Environmental aspects — Israel. - Temperature — Physiological effect. - Urban climatology — Israel.

Présentation (BGU)

Page publiée le 31 décembre 2011, mise à jour le 22 novembre 2018