Outdoor performance of the black globe temperature sensor on a hot and humid tropical region.

A crucial variable to evaluate thermal comfort is the mean radiant temperature (Tmrt). In this paper we evaluate the performance of the 150 mm black globe thermometer to provide reliable Tmrt values for outdoor settings in Singapore. Accurate Tmrt values are calculated by the method of integral radiation measurements. Based on these, the mean convection coefficient of the black globe has been re-calibrated. Results show an improvement in the estimation of Tmrt with the new coefficient in comparison with the default version suggested in ISO7726:1998. Increasing the averaging periods of the measured variables improved the performance of the derived mean convective coefficients to estimate Tmrt. During clear skies day and for 10-min averaged data, RMSE for Tmrt reduce to 3.9 °C (7.4 °C for ISO7726:1998 coefficient) with an overestimation on high incoming solar radiation periods and an underestimation during the morning and evening (low solar elevation). During overcast dry conditions an underestimation of Tmrt is also expected which is higher in the rain/wet periods. The mean convective coefficient presented in this work can provide improved estimations of Tmrt relevant for outdoor thermal comfort studies in hot and humid tropical climates like Singapore.

Numerical analysis of the impact of anthropogenic emissions on the urban environment of Singapore.

Increased urbanization and anthropogenic activities in tropical cities lead to the temperature gradient between the urban and rural environments, causing the urban heat island (UHI) phenomenon. This study is a pioneering attempt that examines the changes in the temporal evolution of the surface energy budget induced by urbanization known as the Anthropogenic Influence (AI) in modifying the urban climate of a tropical city using Weather Research and Forecasting (WRF) numerical modeling system. The AI from buildings, traffic and power plants is determined in five different scenarios and the model is validated with high temporal resolution in-situ data. These increased AIs provide improved WRF capability with root mean square error (RMSE) less than 2 °C and mean bias error (MBE) less than 0.5 °C between different performance indicators. Building envelopes (without indoor activity/equipment) are found to be a major contributor in exacerbating the island wide urban heat ∆TaAI, max to 3.7 °C compared to baseline all green scenario. This is followed by the air-conditioner (AC) systems that contribute up to 1.4 °C. The maximum local contribution of traffic and power plants to urban heat is 0.9 °C and 0.4 °C, respectively.