International Journal of Biometeorology

, Volume 56, Issue 3, pp 481–494 | Cite as

Deriving the operational procedure for the Universal Thermal Climate Index (UTCI)

  • Peter Bröde
  • Dusan Fiala
  • Krzysztof Błażejczyk
  • Ingvar Holmér
  • Gerd Jendritzky
  • Bernhard Kampmann
  • Birger Tinz
  • George Havenith
Special Issue (UTCI)


The Universal Thermal Climate Index (UTCI) aimed for a one-dimensional quantity adequately reflecting the human physiological reaction to the multi-dimensionally defined actual outdoor thermal environment. The human reaction was simulated by the UTCI-Fiala multi-node model of human thermoregulation, which was integrated with an adaptive clothing model. Following the concept of an equivalent temperature, UTCI for a given combination of wind speed, radiation, humidity and air temperature was defined as the air temperature of the reference environment, which according to the model produces an equivalent dynamic physiological response. Operationalising this concept involved (1) the definition of a reference environment with 50% relative humidity (but vapour pressure capped at 20 hPa), with calm air and radiant temperature equalling air temperature and (2) the development of a one-dimensional representation of the multivariate model output at different exposure times. The latter was achieved by principal component analyses showing that the linear combination of 7 parameters of thermophysiological strain (core, mean and facial skin temperatures, sweat production, skin wettedness, skin blood flow, shivering) after 30 and 120 min exposure time accounted for two-thirds of the total variation in the multi-dimensional dynamic physiological response. The operational procedure was completed by a scale categorising UTCI equivalent temperature values in terms of thermal stress, and by providing simplified routines for fast but sufficiently accurate calculation, which included look-up tables of pre-calculated UTCI values for a grid of all relevant combinations of climate parameters and polynomial regression equations predicting UTCI over the same grid. The analyses of the sensitivity of UTCI to humidity, radiation and wind speed showed plausible reactions in the heat as well as in the cold, and indicate that UTCI may in this regard be universally useable in the major areas of research and application in human biometeorology.


Outdoor climate Index Thermal stress Thermophysiology Simulation model Thermal comfort 



This work was supported within the COST Action 730 “Towards a Universal Thermal Climate Index UTCI for Assessing the Thermal Environment of the Human Being”. The stimulating input from the lively discussions with our colleagues within this action is gratefully appreciated. COST is supported by the EU RTD Framework Programme.

Supplementary material

484_2011_454_MOESM1_ESM.pdf (332 kb)
ESM 1–3 (PDF 331 kb) (393 kb)
ESM 4 (ZIP 392 kb)


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Copyright information

© ISB 2011

Authors and Affiliations

  • Peter Bröde
    • 1
  • Dusan Fiala
    • 2
    • 3
  • Krzysztof Błażejczyk
    • 4
  • Ingvar Holmér
    • 5
  • Gerd Jendritzky
    • 6
  • Bernhard Kampmann
    • 7
  • Birger Tinz
    • 8
  • George Havenith
    • 9
  1. 1.Leibniz Research Centre for Working Environment and Human Factors (IfADo)DortmundGermany
  2. 2.Ergonsim – Comfort Energy EfficiencyStuttgartGermany
  3. 3.Institute of Building Technologies, IBBTEUniversity of StuttgartStuttgartGermany
  4. 4.Institute of Geography and Spatial OrganizationPolish Academy of SciencesWarsawPoland
  5. 5.Department of Design Sciences, EATLund UniversityLundSweden
  6. 6.Meteorological InstituteUniversity of FreiburgFreiburgGermany
  7. 7.Department of Safety EngineeringBergische UniversitätWuppertalGermany
  8. 8.Department Climate MonitoringGerman Meteorological ServiceHamburgGermany
  9. 9.Environmental Ergonomics Research Centre, Loughborough Design SchoolLoughborough UniversityLoughboroughUK

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