Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 22 2008 10.5194/acp-8-6597-2008 http://www.atmos-chem-phys.net/8/6597/2008/ http://www.atmos-chem-phys.net/8/6597/2008/acp-8-6597-2008.html http://www.atmos-chem-phys.net/8/6597/2008/acp-8-6597-2008.pdf 6597 6602 2008-11-17 Measurements of UV aerosol optical depth in the French Southern Alps J. Lenoble jacqueline.lenoble@wanadoo.fr C. Brogniez A. de La Casinière T. Cabot V. Buchard F. Guirado Laboratoire d'Optique Atmosphérique (LOA), Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France Interactions Rayonnement Solaire Atmosphère (IRSA), Université Joseph Fourier de Grenoble, 17 Quai Claude Bernard, 38000 Grenoble, France Centre Européen Médical et Bioclimatologique de Recherche et d'Enseignement Supérieur (CEMBREU), 35, rue Croix de Bretagne, Villars St Pancrace, 05100 Briançon, France Routine measurements of global and diffuse UV irradiances at Briançon station (1310 m a.s.l.) are used to retrieve the direct solar irradiance and the aerosol optical depth (AOD), for cloudless days. Data of three years (2003, 2004, 2005) are analyzed; the results confirm those of a preliminary analysis for 2001, 2002. <br><br> The atmosphere is very clear in winter, with AODs between 0.05 and 0.1. The turbidity increases slowly in spring, starting end of February, with AODs around 0.2–0.3 in mid summer, some values reaching 0.4. 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