Offline surface UV

Description

The offline surface ultraviolet (OUV) radiation product contains the following important quantities of solar radiation related to human health: solar noon UV index, daily maximum dose rates and daily integrated doses obtained by different biological weighting functions (action spectra) including erythemal, DNA damage, generalized plant damage, vitamin D synthesis, integrated UV-B and UV-A radiation. In addition, photolysis frequencies of ozone and nitrogen dioxide are included for air quality applications.

Type

Offline. The products are available to users in two weeks from sensing. Usual delay is 3 days.

Theoretical basis

The surface UV products are derived by radiative transfer modelling from the AC SAF total ozone column product and Advanced Very High Resolution Radiometer (AVHRR-3) reflectances, therefore combining data from two different instruments onboard the Metop satellites. Sampling of the diurnal cloud cycle is improved by using additional AVHRR-3 data from the NOAA satellites. See disclaimer at the bottom of this page.

Processing

The product is generated daily at FMI. The dose rates and photolysis frequencies are interpolated from a precomputed look-up table. Daily doses are obtained by integrating over the sunlit part of the day.

Validation

OUV product is validated by FMI. The validation is based on detailed comparison of existing satellite data with ground-based measurements. Visit surface UV validation site for further information.

Online quality monitoring

OUV product quality is constantly monitored by FMI. The online monitoring is based on a tracking value calculated from the daily product. Visit surface UV online quality monitoring page for further information.

Units and spatial resolution

Daily doses are given in (kJ/m²), daily maximum dose rates in (mW/m²) and the photolysis frequencies in (s^-1). The UV index is a unitless scale representing the risk level of skin damage due to UV exposure. All offline UV products are calculated in a 0.5° x 0.5° grid.

Archiving and dissemination

This product is archived at the FMI and available via offline data access page.

File format

Files are in HDF5 format, each file containing global coverage for one day. The size of a single product file is about 19 MB.

Algorithm version information

Time period	GOME-2 / Metop-B	GOME-2 / Metop-C
01.06.2017 - 29.02.2020¹	1.20	N.A.
01.03.2020 onwards	2.2	2.2

¹OUV data before 1 June 2017 is available as data record.

Important algorithm changes in v2.2

Total ozone input: low latitude gaps left by Metop-B are filled with Metop-C data
Surface pressure, albedo and aerosol input: new climatologies
Uncertainties of the inputs are estimated and then propagated (using partial derivatives) to the UV products

Documents

Product user manual (v1.20)
Product user manual (v2.2)
Algorithm theoretical basis document (v1.20)
Algorithm theoretical basis document (v2.2)
Validation report (v1.20)
Validation report (v2.2)