title: Analysis of direct solar ultraviolet irradiance measurements in the French Alps. Retrieval of turbidity and ozone column amount.
abstract: Direct ultraviolet spectral solar irradiance is regularly obtained by the difference between global and diffuse irradiances at the French Alpine station of Briançon; the data of years 2001 and 2002 are analyzed in this paper. Comparison with modeled values is used for cloud screening, and an average UV-A aerosol optical depth is used as an index of turbidity; it is found to be around 0.05 for the clear winter days and around 0.2 in summer. Langley plots are used to verify the instrument calibration; they confirm the expected uncertainty smaller than 5%. The ozone total column amount is estimated with an uncertainty between -3 and Dobson units; comparisons with TOMS (Total Ozone Mapping Spectrometer) overpass values shows agreement within the expected uncertainties of both instruments.
authors.affiliation: Universite Joseph Fourier, Interactions Rayonnement Solaire et Atmosphere, 17, Quai Claude Bernard, 38000, Grenoble, France. jacqueline.lenoble@ujf-grenoble.fr
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Lenoble
authors.forename: Alain
authors.initials: A
authors.lastname: de la Casinière
authors.forename: Thierry
authors.initials: T
authors.lastname: Cabot