Analysis of climatic variables in different urban sites of Singapore and evaluation of strategies to improve the outdoor thermal environment

This report presents the outcome of outdoor thermal comfort campaigns carried out in two different areas of Singapore (commercial and residential/park areas). The aim was to quantify the impact of different urban elements and strategies on the local climate variables and outdoor thermal comfort. In each area, sensors were deployed simultaneously in 4-5 sites to measure air temperature, wind speed and direction, relative humidity, and globe temperature. Evaluation of thermal comfort was done by means of the Physiological Equivalent Temperature heat stress index (PET). Continuous measurements were carried for 4 - 7 months at each site during years 2019 and 2020. The results revealed seasonal OTC differences that justify the necessity of evaluating OTC and its strategies throughout the year. Analysis of vegetation elements has shown a benefit in PET of 7-8°C during the midday/afternoon period. Also shadow from high-rise buildings can produce a decrease of 12°C. Orientation of streets, as well as type of development, have a significant effect on duration, intensity and timing of the diurnal PET peak. Inside each area, during night-time, sites in low-rise developments showed a lower air temperature (1.2-1.5°C) than high-rise areas in agreement with higher sky view factor and higher heat release. On the contrary, during the morning, high-rise street canyons presented a delay in the warming phase that turned into lower air temperature (~0.5°C) compared to low-rise developments. Finally, semi-outdoor spaces (e.g. elevated podiums) can register in the afternoon period up to 13-15°C (PET) lower than close by high-rise developments and 8-9°C (PET) lower than open urban areas, depending on the climatic season. Results provided grounded insights to OTC levels in different urban typologies that can influence decision-making in the context of improving OTC through adequate urban design