How to transform the standing man from a box to a cylinder – a modified methodology to calculate mean radiant temperature in field studies and models

Mean radiant temperature (Tmrt) has shown to be an important meteorological variable in studies of human comfort and health. The Tmrt is defined as the ‘uniform temperature of an imaginary enclosure in which the radiant heat transfer from the human body equals the radiant heat transfer in the actual non-uniform enclosure’ (ASHRAE, 2001). One way to obtain Tmrt is to calculate the surface temperature of a standing man approximated as a cylinder emitting the same amount of longwave radiation as all shortand longwave radiation fluxes received from the surrounding four cardinal points and downand upwards. Fig. 1 shows an example of the equipment that can be used. The calculation was introduced by Höppe in (1992) and has then been used both in models (e.g. SOLWEIG) (Lindberg, Holmer, & Thorsson, 2008) and field studies (Kantor, Kovacs, & Lin, 2014; Kantor, Lin, & Matzarakis, 2014; Thorsson, Lindberg, Eliasson, & Holmer, 2007). However, the formula by Höppe describes in fact a man shaped like a box and not a cylinder as noted by Kantor, Lin, et al. (2014). The box shape has resulted in some peculiar features noticed in studies of Tmrt such as a local minimum at noon (e.g. Kantor, Kovacs, et al. (2014); Kantor, Lin, et al. (2014); Mayer, Holst, and Imbery (2009); Thorsson et al. (2007)) and an influence of the orientation of the field equipment (Kantor, Lin, et al., 2014).These anomalies occur not only in Tmrt calculated from field data but also in model calculations based on the Höppe formula, e.g. SOLWEIG. Thus the anomalies are caused by the calculation method and not connected to shortcomings of the equipment.