UTCI Universal Thermal Climate Index

The assessment of the thermophysiological effects of the atmospheric environment is one of the key issues in human biometeorology. In the past, more than 100 different procedures of various degrees of sophistication have been developed. However, only in the last 30 years significant progress has been made with the development of comprehensive heat budget models which take all significant heat exchange mechanisms into account. Comparisons of the outcome of some of these advanced models show only slight differences. Based on current advances in science and with increased international travel and easy access to information, there is a need for global harmonisation of the development and dissemination of various weather and climatic indices.

Meteorological input data, particularly radiation data, influence the output of comprehensive heat budget models and the question of data availability in various geographical regions needs to be addressed. Another difficult problem is the effective communication of model outcomes to the users (media, public, industry, etc.). Therefore, this Commission will build upon the discussions and recommendations of the recent successful Internet Workshop on Windchill, hosted by Environment Canada (April 3-7, 2000). Considering the recent successful experience with the introduction of a universal UV-index, a "Universal Thermal Climate Index" (working title) shall be developed satisfying the following requirements:

  • thermophysiologically significant in the whole range of heat exchange;
  • valid in all climates, seasons and scales;
  • useful for key applications in human biometeorology (e.g. daily forecasts, warnings, regional and global bioclimatic mapping, epidemiological studies, and climate impact research);
  • independent of person's characteristics (age, gender, specific activities and clothing etc.).
Thermophysiology, i.e. the heat exchange calculation
The Commission will examine different state-of-the-art heat budget models, and will recommend the most appropriate approach in view of the aim of standardisation, e.g. dealing with the "total body", or "just skin cooling", etc.   The model's computer time requirement will also be assessed in terms of routine (operational) applications. 
The problem of the input data is often underestimated, particularly with respect to wind and radiation. Data availability and observational practices in various geographical regions will be addressed in consultation with WMO standards and guidelines. 

UTCI Development Process
The International Society of Biometeorology www.biometeorology.org in 2000 established a Commission on UTCI ISB Commission 6. In 2004 the idea of a new COST Action on UTCI has been launched and meanwhile accepted as .
  • Thermal Comfort Calculator of Richard DeDear
    (based on the sourcecode used by Huizenga et al (1995) in developing ASHRAE's comfort tool):
    • PMV/PPD
    • ET*
    • SET*
    • the main 2-node model's physiological outputs
    • Heat Stress Index (HIS)
UTCI related publications