Column-Integrated Aerosol Optical Properties in the Free Troposphere: Case Study-Sierra Nevada, Spain.

From spectral solar irradiance extinction measuresments in the visible range carried out at Sierra Nevada (2950 m a.s.l.) during July 1998, the characteristics of the aerosol column in the free troposphere have been measured. The results show that in stable atmospheric conditions, the column-integrated aerosol takes an optical depth (AOD) at 500 nm of 0.02 ± 0.02, and an average radius in the accumulation mode of 015 μm, with a likely Atlantic origin. In unstable situations, the AOD at 500 nm can increase by more than an order of magnitude, and the aerosols' origin is uncertain, since air masses can arrive from different sources at different altitudes. [ABSTRACT FROM AUTHOR]