Effect of radiation and wind on thermal comfort in urban environments - Application of the RayMan and SkyHelios model

Abstract Thermal indices are applied frequently for the estimation of thermal comfort and thermal stress of a human being exposed to the prevailing meteorological conditions. Among the most common thermal indices, there is the Perceived Temperature (PT), the Universal Thermal Climate Index (UTCI), and the Physiologically Equivalent Temperature (PET). They are calculated based on the same meteorological input parameters air temperature, vapour pressure, wind speed, and mean radiant temperature. PT, UTCI, and PET can be easily calculated e.g. using RayMan or the SkyHelios model. The meteorological input data for the calculation of thermal indices is to be selected carefully. Parameters with strong spatial fluctuation need to be representative for the desired location. Differences between the instrument height and the target location need to be considered as well. All indices show individual sensitivity to the individual input parameters. However, their responses do mostly agree in terms of tendency as found in a sensitivity analysis in the course of this study. A second part of this study is targeting the spatial applicability of the three thermal indices. While PT and PET are found to be quite suitable, there have been found limitations concerning the applicability of UTCI in spatially resolved analysis.