Quantifying the effect of ground view factor and ground temperature on outdoor mean radiant temperature

The outdoor mean radiant temperature (MRT) is greatly affected by ground radiation related to ground view factor (Fg-p) and ground temperature (Tg). However, the effects of Fg-p and Tg on the MRT are frequently oversimplified and have rarely been quantified. Therefore, this study aims to quantify the effects of Fg-p and Tg on the MRT through microclimate measurement and Monte Carlo ray-tracing simulations. The results suggest that during summers in Shanghai, the effect of Fg-p difference resulting from various human heights on the MRT can be ignored among 70-230-cm-tall individuals when the distance (L) between the edge of the radiant ground area and human body is greater than 40 m. Moreover, the effect of the Fg-p difference resulting from various radiant ground area can be ignored for an individual shorter than 230 cm when the L is not less than 70 m. For ground with a uniform temperature, the MRT may decrease by 6.3 degrees C when Tg is reduced by 16.4 degrees C in Shanghai summer. For ground with non-uniform temperature, the size of the lower-temperature area has a noticeable effect on the MRT. Moreover, averaging the non-uniform Tg may result in an MRT overestimation by 2.5 degrees C for 150-190-cmtall human bodies.