International Journal of Biometeorology

, Volume 60, Issue 11, pp 1775–1785 | Cite as

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

Original Paper


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.


RayMan software package Validations Tmrt PET Urban environment 



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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Copyright information

© ISB 2016

Authors and Affiliations

  1. 1.Chair of Environmental MeteorologyAlbert-Ludwigs-University of FreiburgFreiburgGermany

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