Preliminary characterization of columnar aerosol properties (AOD-AE) at the Saharan Tamanrasset (Algeria) station

Abstract

A Cimel sun photometer has been in operation at Tamanrasset station since late 2006. In this study, more than two years of aerosol measurements have been analyzed from October 2006 to January 2009. Two parameters, aerosol optical depth (AOD) and Ångström exponent (AE), have been used for this preliminar characterization. At this station, the mean AOD is 0.25±0.15 and the mean AE is 0.48±0.23. Both time series data show a clear seasonal cycle. A dry-cool season (fall and winter time), characterized by low AOD and high AE values, and a wet-hot season (in spring-summer), with strong and frequent mineral dust storms, giving high AOD and low AE values, are observed at Tamanrasset. Both, AOD and AE values show the behaviour of a station where desert mineral dust is the prevailing aerosol defining the characteristic of the site. However a significant number of episodes with AE values around 1 together with AOD greater than 0.2 have been found, what suggests the presence of pollution derived aerosols.