ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-11-16439-2011 Use of satellite erythemal UV products in analysing the global UV changes Ialongo I. 1 Arola A. 2 Kujanpää J. 1 Tamminen J. 1 Earth Observation, Finnish Meteorological Institute, Helsinki, Finland Kuopio Unit, Finnish Meteorological Institute, Kuopio, Finland 06 06 2011 11 6 16439 16463 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/11/16439/2011/acpd-11-16439-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/16439/2011/acpd-11-16439-2011.pdf

The amount of surface UV radiation increased during the last 30 years because of the effect of the ozone decrease (from 1979 to 1998) combined with the cloud-aerosol reflectivity changes. Long term changes in solar UV radiation affect the global biogeochemistry, climate and their interactions. During the last decades, satellite UV estimates became available for monitoring the UV level at surface from TOMS (Total Ozone Monitoring System), OMI (Ozone Monitoring Instrument) and GOME-2 (Global Ozone Monitoring Experiment-2) instruments. <br><br> The combined TOMS-OMI dataset of erythemal UV products was applied for the first time to estimate the long-term UV changes at the global scale. The analysis of the uncertainty related to the different input information, is presented. OMI and GOME-2 products were compared in order to analyse the differences in the global UV distribution and their effect on the linear trend estimation. The results showed that the differences in the inputs (mainly surface albedo and aerosol information) used in the retrieval affect significantly the UV change calculation, pointing out the importance of using a consistent dataset when calculating the long term UV changes. The areas where these differences played a major role were located using global maps of monthly UV changes. Despite the uncertainties, significant positive UV changes (ranging from 0 to 6 %/decade) were observed, with higher values on the Southern Hemisphere at mid-latitudes during spring-summer, where the largest ozone decrease was observed.

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