UV radiation monitoring: UV index and UV dose
Forecasts of the UV indexThe 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.
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.
|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|
24 July 2017
data product contact: Jos van Geffen & Ronald van der A
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