Analysis of multiple influential variables on outdoor thermal comfort using numerical simulations in the hot humid climate of Dubai (UAE) -

Abstract

Outdoor thermal comfort is essential to evaluate the quality of urban microclimates. There are several variables that influence outdoor comfort levels. The purpose of this research is to provide an elaborative view of certain variables (vegetation, ground cover, building materials). Dubai Sustainable City, UAE is selected as our case study. The investigation will be done in Dubai's hot arid climate. Field measurements and computer simulations were developed and conducted on December 21 and September 21 in order to achieve the aim and objectives of the study in both winter and summer seasons respectively. Envi-met model was calibrated and proved to be reliable to present selected base case accurately through the correlation of measured and computed experiments. Basic meteorological variables were measured and simulated based on variation in ground cover, vegetation, and building materials to measure the cooling effect performance of each variable. The outcome was used in evaluating the impact of modification and used later to assess its benefits on outdoor thermal comfort. The outdoor thermal comfort was assessed based on Physiological Equivalent Temperature (PET) to evaluate the modification benefits toward outdoor comfort level. It is revealed that vegetation had a better cooling impact than ground cover and building materials due to its ability to limit direct solar exposure and evapotranspiration process within the hottest period of the day 14:00 in Dubai. The study as well revealed the impact of trees density and specifications in altering thermal stress outdoors. Besides, the optimum cooling was recorded upon combining higher tree canopy density with green ground cover as comfort level improved by 5.35 °C versus a 0.65 °C reduction on concrete and vegetation at 15:00 on September 21. Therefore, the study outcomes from the optimum cooling potential of appropriate physical properties of vegetation and ground cover can serve as a guideline in mitigating thermal stress and improve microclimate in o