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Direct spectral irradiance measurements under clear skies have been carried out with a commercial spectroradiometer in the INTA "El Arenosillo" station located in the Gulf of Cadiz (37.1degrees N, 6.7degrees W, sea level) in the south-west of Spain. The measurements started in August of 1996, in order to carry out a climatology of aerosols. Furthermore columnar water vapor is also deter-mined from these spectral measurements. This maritime area is of special interest due to the influence of continental aerosols, Africa desert dust events and local industrial environment. The station of "El Arenosillo" is catalogued as number 213 in the ozone WMO network of Dobson instruments. The MK-III Brewer #150 UV-spectroradiometer is also operative since 1997.

These measurements allow the determination of the aerosol optical depth (AOD) and the (A) over circle ngstrom turbidity parameters in a first step. By means of the spectral behaviour of the AOD we have determined the columnar particle size distribution of atmospheric aerosols using the Mie theory and a pseudo-inversion method, with an adequate choice of the required input parameters. We have derived the physical and radiative parameters during the whole measured period: effective radius, surface and volume and the total vertical mass loading (assuming a given density), asymmetry parameter, single scattering albedo and aerosol phase function. The methodology used has permitted to develop and test a fast procedure based on parameterized expressions between the effective radius and radiative properties, and the (A) over circle ngstrom parameter, This procedure enhanced the importance of the a (A) over circle ngstrom parameter in aerosol studies. Therefore the determination itself of this parameter must be assessed, because of its strong dependence on the spectral range used.