UV radiation monitoring: UV index and UV dose

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UV radiation

UV index
UV dose

Main data product pages: Erythemal UV index  |  Daily erythemal UV dose


Introduction to
UV radiation

UV radiation
UV & health
UV index
forecasts of
UV index
UV dose
1 June 2002


Forecasts of the UV index

The UV index is determined from a parametrisation as function of the otal ozone column (TOC) and the solar zenith angle at local solar noon. The TOC at local solar noon in turn follows from data assimilation of satellite observations of ozone, using meteorological fields (wind, temperature, pressure) from the European Centre for Medium-Range Weather Forecasts (ECMWF).

A forecast of the meteorological fields is available from the ECMWF. This enables a forecast of the global ozone field for a few days ahead. And from that it is possible to provide a forecast of the clear-sky UV index for a few days ahead -- see the near-real time UV index page.

Forecasts the UV index a few days ahead make it possible to issue warnings of possibly dangerously high values of UV radiation at the ground, that is: values markedly higher than normal for a given region.

High UV index values are due to low ozone column values. The lowest ozone column values are found in the Antarctic ozone hole. Normally these areas of low ozone are only above the Antarctic continent and the seas around it, where not many people live.

On 12 October 2000, though, the situation was rather different: a tip of the ozone hole reached the southern tip of Southern America.

ozone column at 12 Oct. 2000
UV index at 12 Oct. 2000
Local solar noon ozone columns in Dobson Units [DU] and clear-sky UV index values (1 unit equals 25 mW/m2) for 12 October 2000. Note the low ozone values above the southern of Southern America, with values around 140 DU, leading to unusually high UV index values.

In combination with the solar zenith angle, which is higher for lower latitudes, low ozone column values lead to unusually high UV index values for this point of the south of Argentina and Chile, notably the area around the town of Ushuaia, where the UV index reached the value 12.4. UV index Values of 10 and more were reached in a much larger area, as the following plot shows.

UV index at 12 Oct. 2000
Clear-sky UV index values (1 unit equals 25 mW/m2) for 12 October 2000 above the southern tip of South America. The highest value is just west of the town Ushuaia.
map of southern South America Map of the southern part of South America, adapted from a map taken from the South America reference map 2002 found at the Perry-Castañeda Library Map Collection.

town inhabitants elevation longitude latitude ozone column UV index
Ushuaia 69,500 268 m -68.30 -54.80 137.6 DU 12.4
Punta Arenas 120,000 0 m -70.93 -53.17 155.7 DU 10.7
Río Gallegos 75,000 41 m -69.22 -51.63 169.6 DU 10.0


last modified: 24 July 2017
data product contact: Jos van Geffen & Ronald van der A
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