Aerosol characterization at the Saharan AERONET site Tamanrasset

C. Camino,S. Alonso-Pérez,P. Goloub,A. M. de Frutos,J. M. Baldasano,C. Guirado,C. Toledano,J. J. Bustos,E. Cuevas,M. Mimouni,S. Basart,L. Zeudmi,V. E. Cachorro,P. M. Romero

doi:10.5194/acp-14-11753-2014

Abstract

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.

Highlights

The regional characterization of mineral dust, close to source areas, has become a valuable tool for researchers from different fields
This station is involved in several international measurement programs such as the Global Climate Observing System (GCOS) – Upper-Air Network (GUAN), the Baseline Surface Radiation Network (BSRN), and the Global Atmospheric Watch (GAW) program of the World Meteorological Organization (WMO)
Once we have identified and confirmed all the MCS events impacting Tamanrasset, the Moderate Resolution Imaging Spectroradiometers (MODIS) Deep Blue 550 nm aerosol optical depth (AOD) retrieval has been used in a similar approach to Roberts (2014) and Roberts et al (2014)

Summary

Introduction

The regional characterization of mineral dust, close to source areas, has become a valuable tool for researchers from different fields. C. Guirado et al.: Aerosol characterization at the Saharan AERONET site Tamanrasset recent years, several field campaigns in different locations focused on the analysis of Saharan dust features (Todd et al, 2013, and references therein). Tamanrasset (main city in the Hoggar, known as Ahaggar Mountains, in Algeria) hosted a specific soil and aerosol sampling analysis at the beginning of the 1980s (D’Almeida and Schütz, 1983), the African turbidity monitoring network (1980–1984) for climate modelling purposes (D’Almeida, 1986, 1987), and the more recent African Monsoon Multidisciplinary Analysis (AMMA) campaign (Redelsperger et al, 2006)

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