Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 10 3 2010 10.5194/nhess-10-421-2010 http://www.nat-hazards-earth-syst-sci.net/10/421/2010/ http://www.nat-hazards-earth-syst-sci.net/10/421/2010/nhess-10-421-2010.html http://www.nat-hazards-earth-syst-sci.net/10/421/2010/nhess-10-421-2010.pdf 421 428 2010-03-05 Comparison of aerosol optical thickness with in situ visibility data over Cyprus A. Retalis adrianr@meteo.noa.gr D. G. Hadjimitsis S. Michaelides F. Tymvios N. Chrysoulakis C. R. I. Clayton K. Themistocleous Institute for Environmental Research and Sustainable Development, National Observatory of Athens, Athens, Greece Department of Civil Engineering and Geomatics, Cyprus University of Technology, Limassol, Cyprus Meteorological Service, Nicosia, Cyprus Institute of Applied and Computational Mathematics, Foundation for Research and Technology – Hellas, Heraklion, Crete, Greece Department of Civil Engineering and Environment, University of Southampton, Southampton, UK The monitoring of aerosol concentrations comprises a high environmental priority, particularly in urban areas. Remote sensing of atmospheric aerosol optical thickness (AOT) could be used to assess particulate matter levels at the ground. However, such measurements often need further validation. In this study, aerosol data retrieved from satellite and sun-photometer, on the one hand, and visibility data at various locations in Cyprus, on the other hand, for the period from January to June 2009 are contrasted. The results obtained by the direct comparison between MODIS and handheld sun-photometer AOT data exhibited a significant correlation (<i>r</i>=0.83); these results are in agreement with those reported by the National Aeronautics and Space Administration (NASA). The correlation between sun-photometer AOT and that estimated from visibility measurements was also significant (<i>r</i>=0.76). A direct and significant relationship between MODIS AOT and AOT estimated from visibility values was also found for all the locations used (the correlation coefficient was found to vary from 0.80 to 0.84). It is concluded that MODIS AOT data provide accurate information on the aerosol content in Cyprus, while in the absence of such data, visibility measurements could be used as a secondary source of aerosol load information, in terms of aerosol optical thickness, and provide useful information on a near-real time basis, whenever data are available. 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