Abstract
The modelling of thermal exposure in outdoor urban environments is a highly topical challenge in modern climate research. This paper presents the results derived from a new micrometeorological model that employs an integrated biometeorology module to model Universal Thermal Climate Index (UTCI). This is PALM-4U, which includes an integrated human body-shape parameterization, deployed herein for a pilot domain in Prague, Czech Republic. The results highlight the key role of radiation in the spatiotemporal variability of thermal exposure in moderate-climate urban areas during summer days in terms of the way in which this directly affects thermal comfort through radiant temperature and indirectly through the complexity of turbulence in street canyons. The model simulations suggest that the highest thermal exposure may be expected within street canyons near the irradiated north sides of east–west streets and near streets oriented north–south. Heat exposure in streets increases in proximity to buildings with reflective paints. The lowest heat exposure during the day may be anticipated in tree-shaded courtyards. The cooling effect of trees may range from 4 °C to 9 °C in UTCI, and the cooling effect of grass in comparison with artificial paved surfaces in open public places may be from 2 °C to 5 °C UTCI. In general terms, this study illustrates that the PALM modelling system provides a new perspective on the spatiotemporal differentiation of thermal exposure at the pedestrian level; it may therefore contribute to more climate-sensitive urban planning.
Highlights
Human thermal environments have attracted the interest of many researchers in recent decades [1], and their conclusions have found applications in a wide range of fields, including public health, medicine, physiology, sport, biometeorology, and engineering [1]
The particular aims of this investigation were (a) to analyze the spatiotemporal patterns of thermal exposure in a moderate-climate urban area during summer days in the context of key environmental parameters of the human thermal environment—mean radiant temperature (MRT), air temperature (T), humidity (H), and wind speed (v); (b) to provide detailed analyses of the temporal variability of thermal exposure based on the Universal Thermal Climate Index (UTCI) index in a range of selected public urban places; and (c) to discuss further improvements to and application of the model in an analysis of thermal comfort in a complex urban environment and its practical usefulness in urban planning
Such low UTCI values are mainly attributable to a lower MRT associated with more rapid radiative cooling due to a large sky-view factor
Summary
Human thermal environments have attracted the interest of many researchers in recent decades [1], and their conclusions have found applications in a wide range of fields, including public health, medicine, physiology, sport, biometeorology, and engineering [1]. The particular aims of this investigation were (a) to analyze the spatiotemporal patterns of thermal exposure in a moderate-climate urban area during summer days in the context of key environmental parameters of the human thermal environment—mean radiant temperature (MRT), air temperature (T), humidity (H), and wind speed (v); (b) to provide detailed analyses of the temporal variability of thermal exposure based on the UTCI index in a range of selected public urban places; and (c) to discuss further improvements to and application of the model in an analysis of thermal comfort in a complex urban environment and its practical usefulness in urban planning
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