Empirical calibration of thermal indices in an urban outdoor Mediterranean environment

Abstract

Thermal indices are important for assessing human thermal perception and are widely used as indicators of heat strain as well as for designing, tourism and forecast purposes. This research focuses on thermal sensation scales calibration of a large number of thermal indices in order to be applied with greater success in outdoor urban environments in Mediterranean climatic zones. Field questionnaire surveys were carried out during three different seasons monitoring microclimatic variables and subjective characteristics while interviewees were asked to indicate their thermal sensation based on a seven point thermal sensation scale. Three calibration methods, linear and cubic regression as well as probit analysis, were applied and compared based on three statistical criteria. Indices' predictions according to the calibrated scales were evaluated aiming to designate the one that best simulates thermal sensation. Probit analysis calibrated indices assessment scales more adequately compared to linear or cubic regression. Overall Actual Sensation Vote (ASV), Subjective Temperature Index (STI) and Universal Thermal Climate Index (UTCI) based on the calibrated scales showed the best predictability of thermal sensation vote compared to all the indices studied.