Caractérisation d'un photomètre solaire conçu pour l'étude des propriétés optiques des aérosols atmosphériques

The atmosphere contains molecules, clouds and aerosols. These latter sub-millimeter particles have a large variability in size, shape, chemical composition, lifetime and contents. Their concentration depends much on geographical situations, meteorological and environmental conditions. This variability makes it difficult to assess aerosol climatology. Setting up a solar photometer ( automatic, autonomous and portable instrument ) on a given site, allows to carry out necessary measurements for aerosol characterization. Particle microphysical and optical properties are obtained from photometric measurements. Two kinds of measurements can be carried out : a direct aim towards the sun ( ‘ SUN measurements’ ) or a scan of the sky ( ‘SKY measures’ ). The first measurements are used to compute aerosol optical thickness ( or abundance ) at four wavelengths and to retrieve total precipitable water. Second kind allows the determination of aerosol size distribution. A CIMEL photometer has been installed at Thala site ( Tunisia ) by LOA ( Laboratoire d’Optique Atmospherique, Lille ) and has been operating for March – October 2001 period by the EMAGPOT Franco Tunisian project. Different photometric data supplied during this period, allowed us to deduce interesting results concerning environmental conditions of the studied region and to prove the influence of various kinds of aerosols on air pollution and on radiation passing through the atmosphere. Mots-clefs : photometre solaire ; aerosols ; pollution atmospherique