DIURNAL ATMOSPHERIC EXTINCTION OVER TEIDE-OBSERVATORY (TENERIFE, CANARY-ISLANDS)

Data from five continuous years (1984 to 1989) at Teide Observatory (I zana, Tenerife, Canary Islands) obtained with a full-disc solar multic hannel photometer devoted to the detection of solar intensity oscillat ions has now been used for a detailed study of the extinction coeffici ent behaviour at several wavelengths (from 450 nm to 870 nm) and aeros ol size distributions under different atmospheric conditions. From thi s study we conclude that an extinction coefficient around 0.075 mag ai rmass(-1) at 680 nm constitutes the borderline between clear days and dusty days affected by the occasional presence of wind-blown Saharan d ust. In the former the extinction can vary between 0.04 and 0.07 mag a irmass(-1) (at 680 nm) and in the latter between 0.075 and 0.8 mag air mass(-1) (at 680 nm). Moreover the dust produces a grey effect in the wavelength range analysed in this work. From the extinction coefficien ts we use inversion methods to compute the particle size distribution in both atmospheric conditions. Approximately, the extinction on clear and dusty days is produced by aerosol particles with radius between 4 0 and 120 nm and between 120 and 3000 nm, respectively.