Volume 17, No. 3, March 2017, Pages 875-887 PDF(1.8 MB)
Measurements of Aerosol Optical and Microphysical Properties in Tizi Ouzou
Dehia Belaidi1,2, Philippe Goloub2, Soltane Ameur1, Thierry Podvin2, Abdenour Ambar3, Zohra Ameur1
1 Laboratoire d'Analyse et de Modélisation des Phénomènes Aléatoires (LAMPA), Université de Mouloud Mammeri, Tizi-Ouzou 15000, Algérie
2 Laboratoire d'Optique Atmosphérique (LOA), CNRS, UMR8518, Université Lille1, 59655 Villeneuve d’Ascq, France
3 Office National de la Météorologie ONM d’Alger, Dar El Beida 16011, Algérie
- Lidar and sun photometer, are combined for the first time in southern Mediterranean.
- Three years of observation in Tizi Ouzou have shown a wide variability of aerosols.
- The dust aerosols are often found at the high Layer between 1.5 and 5 km.
- Pollution of southern Europe is detected in north African.
To characterize the optical behavior of atmospheric particles located above the region of Tizi Ouzou, a micro-LIDAR and a sun/sky-photometer have been used. The analysis of three years of observation has revealed a large variability in the optical properties of the particles present in the atmosphere of this region. The aerosol extinction optical depth (τ) at 500 nm varies from 0.03 to about 2. The Angstrom Exponent (α), in the range 440–870 nm, varies from 0 to 1.8 and is indicating a large variability in size. The combination of micro LIDAR and sun/sky photometer measurements allowed us to determine the vertical profiles of the aerosol extinction coefficient (σext). The vertical profile helps to separate local from transported particles origins. The observation site is located in the city and surrounded by high mountains (2300 m asl). The aerosol optical depth at 500 nm and the Angstrom exponent respectively having the values τ > 0.5 and α < 0.25 indicate the high presence of desert dust particles from Saharan origin. This type of particles is frequently observed for α ranging between 0.25 and 0.35. The analysis of back-trajectories helped to identify the probable origin of air masses affecting the region. Our results show that a routinely operating LIDAR / photometer observing system coupled with back-trajectories analysis is a relevant tool for aerosols monitoring. They show, for the first time, the high temporal variability of aerosols present in the atmosphere of the Tizi Ouzou region.
Micro LIDAR; Sun/sky-photometer; Optical properties; Vertical profile; Desert dust.