UV index & UV dose based on GOME	UV radiation monitoring
Overview of the data product archive

Example of the erythemal UV dose validation

Ground-based measurements of UV radiation are performed on several sites in Europe and the data of these measurements is collected in the European Database for UV Climatology and Evaluation (EDUCE). This database allows to download individual spectra for intercomparison, validation, etc. The BASINT tool of the EDUCE website allows to extract the erythemal UV dose rate computed from these spectra.

As an example of the validation the erythemal UV dose rate as reported by the BASINT tool is compared with the erythemal UV dose computed for TEMIS. The UV algorithm computes UV doses in 10-minute intervals and sums these to find the daily dose. To facilitate the comparison, the dose rate of the BASINT tool (given in J/m²s) has been integrated over 10 minutes as well for each of the measurements.

The following graphs show a comparison between the 10-minute erythemal UV dose (in kJ/m²) as derived from the BASINT tool and the TEMIS results for three typical cases in 2002, on days which were completely cloud-free between at least 08h and 14h UTC according to the METEOSAT data. Also shown is the UV dose assuming full cloud cover ("overcast"). The table presents the UV dose integrated over the whole day. These three cases show the range of the expected difference between groundbased measurements and the TEMIS product.

For Lampedusa (Italy) on 14 July 2002, the results are almost identical. On 28 May 2002 there is a notable difference: the Lampedusa station gives distinctly higher UV doses than the estimate by the TEMIS method. Obviously, 28 May was a very clear day, with less aerosols than the average at De Bilt and Paramaribo, which is currently accounted for in the parametrisation of the UV index.

For Thessaloniki on 28 June 2002 the situation is reversed: the ground station gives distinctly lower UV dose values than the TEMIS method. This difference could be due to the enhanced presence of aerosols at Thessaloniki. Also the presence of small clouds at the moments of the measurement, which do not show up in the METEOSAT data, may cause a smaller UV dose derived from the groundbased measurements.

10-minute erythemal UV dose rate (in kJ/m2) for three typical cases in 2002, on days which were completely cloud-free between at least 08h and 14h UTC. The red line shows the UV dose rate as computed from the TEMIS data, using the METEOSAT cloud cover. The blue line shows the UV dose rate derived with the BASINT tool of the EDUCE website, where each square represents a measurement point. The green line shows the UV dose rate assumming full cloud cover ("overcast").

groundstation	date	daily UV dose (kJ/m2)
		Meteosat	BASINT	overcast
Lampedusa	28 May 2002	4.84	5.31	2.42
Lampedusa	14 July 2002	4.86	4.83	2.43
Thessaloniki	28 June 2002	5.32	4.82	2.69

last modified: January 2006
data product contact: Jos van Geffen & Ronald van der A
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