9B.8: The Influence of Anisotropic Diffuse Radiation on Mean Radiant Temperature in Outdoor Urban Environments

• One of the most important meteorological variables when estimating outdoor thermal comfort is the mean radiant temperature (Tmrt). Tmrt is estimated from the flux of short-wave and long-wave radiation between a human and its surroundings. During clear weather conditions the main part of the short-wave irradiance originates from Sun direct-beam radiation. However, part of the short-wave radiation is also originating from all-sky diffuse radiation. As of now most models for radiant load simulations considers the sky to be isotropic when estimating diffuse radiation. This leads to misinterpretations of the diffuse radiation, especially close to walls where the sky-view factor controls the amount of radiation that reaches the ground. Here we use the SOLWEIG model to examine the effects of an anisotropic diffuse model (Perez et al. in 1993) on short wave radiant loads as well as Tmrt for pedestrians in outdoor urban environment. Comparisons between the anisotropic model and the isotropic model indicates that the diffuse radiation in the isotropic model is overestimated in areas in front of north facing walls and underestimated in areas in front of south facing areas. These deviations, in turn, have implications for the Tmrt. The deviations in diffuse radiation thus signifies the importance of using an anisotropic model when estimating diffuse radiation and Tmrt, especially in densely built areas where the sky-view factor controls large parts of the radiation that reaches the ground.

Subject headings

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Klimatforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Climate Research (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Meteorologi och atmosfärforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Meteorology and Atmospheric Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Naturgeografi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Physical Geography (hsv//eng)

Publication and Content Type

vet (subject category)

kon (subject category)