Twenty-five years of spectral UV-B measurements over Canada,Europe and Japan: Trends and effects from changes in ozone,aerosols, clouds,and surface reflectivity |
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| Institution: | 1. Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece;2. Navarino Environmental Observatory (N.E.O.), Costa Navarino, Messinia, Greece;3. Faculty of Geology and Geoenvironment, University of Athens, Athens, Greece;4. Research Centre for Atmospheric Physics and Climatology, Academy of Athens, Athens, Greece;5. Meteorological Research Institute, Japan Meteorological Agency, Ibaraki, Japan;6. Air Quality Research Division, Environment and Climate Change Canada, M3H 5T4 Toronto, Canada;7. Royal Meteorological Institute of Belgium, Ringlaan 3, 1180 Brussels, Belgium;8. Finnish Meteorological Institute–Space and Earth Observation Centre, Sodankylä, Finland;9. Finnish Meteorological Institute, Climate Research, Helsinki, Finland;10. Centre for Atmospheric Sciences, School of Earth and Environmental Sciences, University of Manchester, Manchester, UK |
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| Abstract: | Spectral UV records of solar irradiance at stations over Europe, Canada, and Japan were used to study long-term trends at 307.5 nm for a 25-year period, from 1992 to 2016. Ground-based measurements of total ozone, as well as satellite measurements of the Aerosol Index, the Total Cloud Cover and the surface reflectivity were also used in order to attribute the estimated changes of the UV to the corresponding changes of these factors. The present study shows that over the Northern Hemisphere, the long-term changes in UV-B radiation reaching the Earth's surface vary significantly over different locations, and that the main drivers of these variations are changes in aerosols and total ozone. At high latitudes, part of the observed changes may also be attributed to changes in the surface reflectivity. Over Japan, the UV-B irradiance at 307.5 nm has increased significantly by ～3%/decade during the past 25 years, possibly due to the corresponding significant decrease of its absorption by aerosols. It was found that the greatest part of this increase took place before the mid-2000s. The only European station, over which UV radiation increases significantly, is that of Thessaloniki, Greece. Analysis of the clear-sky irradiance for the particular station shows increasing irradiance at 307.5 nm by ～3.5%/decade during the entire period of study, with an increasing rate of change during the last decade, possibly again due to the decreasing absorption by aerosols. |
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| Keywords: | Solar UV radiation Total ozone Clouds Surface reflectivity UV-B |
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