UV index and UV dose: surface elevation correction
|Main data product description page|
Surface elevation correctionThe amount of UV radiation received by someone at the Earth's surface is affected by the local surface elevation: the higher the surface, the more UV radiation. For this reason the UV index and UV dose calculation applies a 5% increase of the incident UV irradiance per km surface elevation above sea level:f(H) = 1 + 0.05·Hwhere the surface elevation
H(in km w.r.t. sealevel) is determined from the GMTED2010 global digital elevation model, which is averaged to the UV grid resolution of 0.25°×0.25°.
The averaging of the GMTED2010 data over the UV grid cell provides also a standard deviation, which is propagated to the UV index and UV dose error estimates.
GMTED2010 based surface elevation data (left) and standard deviation (right)
at the UV grid resolution of 0.25°×0.25°.
Note on the percentage increase per kmThe TEMIS UV dose service provides the UV dose for three action spectra. The increase of the UV radiation with 5% per km elevation mentioned above is an estimate made for the erythemal UV radiation, i.e. for the UV radiation covering both the UV-A and UV-B wavelenghts.
The other two action spectra, vitamin-D and DNA-damage, stress the shorter UV-B wavelengths much more, and for those data products the percentage increase might well be 10% or more.
For reasons of practicality we have chosen to use one percentage for all TEMIS UV data products.
- For some more info on the GMTED2010 data, its source and description, and for download of the data averaged to different resolutions, see this page.
19 February 2019
data product contact: Jos van Geffen & Michiel van Weele & Ronald van der A
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