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Validation of the mean radiant temperature simulated by the RayMan software in urban environments

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Abstract

The RayMan software is worldwide applied in investigations on different issues in human-biometeorology. However, only the simulated mean radiant temperature (T mrt) has been validated so far in a few case studies. They are based on T mrt values, which were experimentally determined in urban environments by use of a globe thermometer or applying the six-directional method. This study analyses previous T mrt validations in a comparative manner. Their results are extended by a recent validation of T mrt in an urban micro-environment in Freiburg (southwest Germany), which can be regarded as relatively heterogeneous due to different shading intensities by tree crowns. In addition, a validation of the physiologically equivalent temperature (PET) simulated by RayMan is conducted for the first time. The validations are based on experimentally determined T mrt and PET values, which were calculated from measured meteorological variables in the daytime of a clear-sky summer day. In total, the validation results show that RayMan is capable of simulating T mrt satisfactorily under relatively homogeneous site conditions. However, the inaccuracy of simulated T mrt is increasing with lower sun elevation and growing heterogeneity of the simulation site. As T mrt represents the meteorological variable that mostly governs PET in the daytime of clear-sky summer days, the accuracy of simulated T mrt is mainly responsible for the accuracy of simulated PET. The T mrt validations result in some recommendations, which concern an update of physical principles applied in the RayMan software to simulate the short- and long-wave radiant flux densities, especially from vertical building walls and tree crowns.

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Acknowledgments

The authors would like to thank Dr. Jutta Holst for providing quality-checked results of the human-biometeorological field studies conducted on 27 July 2009 in Freiburg.

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  1. Chair of Environmental Meteorology, Albert-Ludwigs-University of Freiburg, Werthmannstrasse 10, 79085, Freiburg, Germany

    Hyunjung Lee & Helmut Mayer

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  1. Hyunjung Lee
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  2. Helmut Mayer
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Correspondence to Hyunjung Lee.

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Lee, H., Mayer, H. Validation of the mean radiant temperature simulated by the RayMan software in urban environments. Int J Biometeorol 60, 1775–1785 (2016). https://doi.org/10.1007/s00484-016-1166-3

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