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UTCI

The calculation of UTCI is based on a 6th order polynomial regression function estimating UTCI from wind speed, air temperature, mean radiant temperature and air vapour pressure (see COST 730 Webpage). Due to that approach, there is almost nothing that can be changed in the personal settings such as clothing, activity etc.

Limits:

  • Wind Speed: UTCI as used in the software is limited to a wind speed range of 0.5 to 17 m/s related to 10 m Height
  • Height reference: UTCI always related to wind speed at 10 m height while the biometeorological parameters are normally define between 1.5 and 2 m…

As UTCI refers to the 10 m level, ENVI-met BioMet rescales the outputs for the required level (pedestrian lvel) using the 10 m level data using the logarithmic wind power profile $$v_{10m} := ln(10 / z0) / ln(zlevel / z0) * wind10m$$

Obviously, that doesn't make much sense as the $z0$ roughness value is unkown for most sites, but ENVI-met provides detailed and calculated wind flow data for all levels. We recommend to use PET instead.

Please Note: Due to these restrictions, areas outside the official bounds of UTCI will not be calculated by BioMet. These areas are marked with “No Data”. Especially in urban areas, the lower limit of 0.5 m/s can create a number of white “No Data” areas in the maps. In future versions of BioMet, will add an option to ignore these UTCI bounds. BUT: Remember that UTCI is not a part of ENVI-met. Using this option, your maps might look better and more complete. But scientifically, you are leaving the “official” and pre-calcuated UTCI range.

References

Link to the original source code and to the EU COST Action 730 Homepage: http://www.utci.org/utci_doku.php

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