Thermal Comfort Indices - Universal Thermal Climate Index, 1979-2020

Context The universal thermal climate index (UTCI) is a human biometeorology parameter that is used to assess the linkages between outdoor environment and human well‐being. Thermal comfort indices describe how the human body experiences atmospheric conditions, specifically air temperature, humidity, wind and radiation.

Definition The universal thermal climate index (UTCI) is an equivalent temperature (°C), it is a measure of the human physiological response to the thermal environment. The universal thermal climate index (UTCI) describes the synergistic heat exchanges between the thermal environment and the human body, namely its energy budget, physiology and clothing. UTCI takes into consideration the clothing adaptation of the population in response to actual environmental temperature. There are four variables required to calculate the UTCI: 2m air temperature, 2m dew point temperature (or relative humidity), wind speed at 10m above ground level and mean radiant temperature (MRT).

Data Sources The universal thermal climate index (UTCI) is computed using data from the ECMWF ERA5 reanalysis.

Understand There are 10 UTCI thermal stress categories that correspond to specific human physiological responses to the thermal environment. The categories relate to UTCI values as follows: above +46: extreme heat stress; +38 to +46: very strong heat stress; +32 to +38: strong heat stress; +26 to +32: moderate heat stress; +9 to +26: no thermal stress; +9 to 0: slight cold stress; 0 to -13: moderate cold stress; -13 to -27: strong cold stress; -27 to -40: very strong cold stress; below -40: extreme cold stress.

Supporting Information The data was collated on behalf of the Copernicus Climate Change Service (C3S). Further information about this index can be found in the C3S documentation resources in the Climate Data Store.

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Visualisation and Navigation The universal thermal climate index (UTCI) for each month and year from 1979 to 2020 is plotted on a map showing the European NUTS aggregation regions. The EUROSTAT NUTS classification (Nomenclature of Territorial Units for Statistics) is a hierarchical system for dividing up the economic territory of Europe. The size of the regions shown on the map can be adjusted by selecting the appropriate NUTS level: national level (NUTS-0), first sub-national level (NUTS-1), and second sub-national level (NUTS-2).

The regions on the map facilitate dynamic access to the underlying data. Hover the mouse pointer over a region to view its name or click on a region to request a time series plot. Likewise, the trans-national average for the EEA member and cooperating countries (EEA 38) can be accessed via the "Europe" bounding box.

The time series plot shows the area mean UTCI for the chosen region.

Click and hover the mouse over the time series plot to view the data values and to reveal action buttons for features such as “zoom” and “download plot as a png”. Links below the plot enable the download of time series data in the spreadsheet compatible .csv format.