Comparison of measured and modelled mean radiant temperature in the tropical urban environment

RayMan is the most popular software package for thermal comfort research and urban planning. RayMan simulates the mean radiant temperature (Tmrt) and provides assessment of the human-biometeorology for urban areas. In this study Tmrt simulated by RayMan (version 1.2) has been validated with results from the six-directional radiation measurements in tropical urban settings in Malaysia. In addition, a validation of the physiologically equivalent temperature (PET) simulated by RayMan is conducted for the first time in the tropical context. Tmrt values from RayMan1.2 show some agreement with the measured values during middle of the validated days; however there was high fluctuation over that time due to rapid changes in radiation by cloud appearing. The results also show that RayMan1.2 considerably underestimated Tmrt during morning and evening. The simulated PET values followed the same pattern of the simulated Tmrt. However the simulated PET had a closer estimation to the experimentally obtained PET. The study also noted that RayMan1.2 accuracy seems to be site-related. Its simplification to the 3-D radiation environment led to variations in simulation accuracy depending on urban morphology. Therefore improvements of the RayMan software for simple and complex urban settings and tropical climates are required.