Articles | Volume 14, issue 21
Atmos. Chem. Phys., 14, 11753–11773, 2014
Atmos. Chem. Phys., 14, 11753–11773, 2014

Research article 11 Nov 2014

Research article | 11 Nov 2014

Aerosol characterization at the Saharan AERONET site Tamanrasset

C. Guirado1,2, E. Cuevas2, V. E. Cachorro1, C. Toledano1, S. Alonso-Pérez2,3,4, J. J. Bustos2, S. Basart5, P. M. Romero2, C. Camino2, M. Mimouni6, L. Zeudmi6, P. Goloub7, J. M. Baldasano5,8, and A. M. de Frutos1 C. Guirado et al.
  • 1Atmospheric Optics Group, University of Valladolid (GOA-UVA), Valladolid, Spain
  • 2Izaña Atmospheric Research Center (IARC), State Meteorological Agency of Spain (AEMET), Santa Cruz de Tenerife, Spain
  • 3Institute of Environmental Assessment and Water Research, Spanish National Research Council (CSIC), Barcelona, Spain
  • 4Universidad Europea de Canarias, Laureate International Universities, La Orotava, Spain
  • 5Earth Sciences Department, Barcelona Supercomputing Center-Centro Nacional de Supercomputación, BSC-CNS, Barcelona, Spain
  • 6Office National de la Météorologie, Direction Méteo Regionale Sud, Tamanrasset, Algeria
  • 7Laboratoire d'Optique Atmosphérique, Université des Sciences et Technologies de Lille, Lille, France
  • 8Environmental Modeling Laboratory, Technical University of Catalonia, Barcelona, Spain

Abstract. More than 2 years of columnar atmospheric aerosol measurements (2006–2009) at the Tamanrasset site (22.79° N, 5.53° E, 1377 m a.s.l.), in the heart of the Sahara, are analysed. Aerosol Robotic Network (AERONET) level 2.0 data were used. The KCICLO (K is the name of a constant and ciclo means cycle in Spanish) method was applied to a part of the level 1.5 data series to improve the quality of the results. The annual variability of aerosol optical depth (AOD) and Ångström exponent (AE) has been found to be strongly linked to the convective boundary layer (CBL) thermodynamic features. The dry-cool season (autumn and winter) is characterized by a shallow CBL and very low mean turbidity (AOD ~ 0.09 at 440 nm, AE ~ 0.62). The wet-hot season (spring and summer) is dominated by high turbidity of coarse dust particles (AE ~ 0.28, AOD ~ 0.39 at 440 nm) and a deep CBL. The aerosol-type characterization shows desert mineral dust as the prevailing aerosol. Both pure Saharan dust and very clear sky conditions are observed depending on the season. However, several case studies indicate an anthropogenic fine mode contribution from the industrial areas in Libya and Algeria. The concentration weighted trajectory (CWT) source apportionment method was used to identify potential sources of air masses arriving at Tamanrasset at several heights for each season. Microphysical and optical properties and precipitable water vapour were also investigated.

Short summary
Tamanrasset, in the heart of the Sahara, is a key site for aerosol research. The analysis of more than 2 years (2006-2009) of AERONET and KCICLO-corrected sun photometer measurements shows that atmospheric aerosols at Tamanrasset are modulated by the Convective Boundary Layer leading to pure Saharan dust conditions (April-September) and very clear sky conditions (November-February). Dust potential sources and anthropogenic fine aerosols arriving at Tamanrasset are also identified.
Final-revised paper