Near real-time clear-sky UV index


The near real-time clear-sky UV index provides one day global forecast of expected UV index under clear-sky conditions.


Near real-time. The product is ready for dissemination 03:00 UTC at the latest.

Theoretical basis

The product is based on GOME-2/Metop-B and GOME-2/Metop-C assimilated total ozone (ATO) from KNMI. UV index is calculated from ATO applying climatologies for surface albedo, aerosol optical depth etc. The final product is valid for clear-sky conditions at local noon, i.e. minimum solar zenith angel, thus reflecting the maximum UV index to be expected for the current day. GOME2-B and GOME2-C products are produced in parallel and are both available, but GOME2-C is considered as the primary result and is disseminated to the end users.

Processing algorithm

Assimilated total ozone data is processed at the DMI using NUV software. The data processor reads the ATO data and calculates UV index for each data point in the ATO file.

Units and spatial resolution

UV index is a unit of measure of UV levels relevant to the effects on human skin. It is expressed numerically as the equivalent of multiplying the time weighted average effective irradiance (W/m2) by 40. The UV index maps are calculated in the same grid size as the input ATO field, with a sub-pixel altitude correction resolution of 0.25° x 0.25°.


This product is validated by the DMI. Validation is based on detailed comparison with ground-based measurements.

Online quality monitoring

The product quality is constantly monitored by DMI. On the NUV website various quality plots and files are updated daily.


See NRT access information.

File format

This product is available as global and continental maps in PNG image format. Users can request the whole or partial dataset in various data formats and/or delivery methods, see NRT access information.

Algorithm version information

Time period GOME-2 / Metop-A GOME-2 / Metop-B GOME-2 / Metop-C
11.02.2009 – 01.06.2010 1.4 N.A. N.A.
02.06.2010 - 28.08.2012 3.1 N.A. N.A.
29.08.2012 - 13.07.2013 3.2 N.A. N.A.
14.07.2014 - 15.07.2020 N.A. 3.3 N.A.
16.07.2020 onwards N.A. 3.3 3.3


The most recent near real-time clear-sky UV index from the Metop-C satellite