Daily and monthly averaged aerosol optical properties and diurnal variability deduced from AERONET sun-photometric measurements at Thala site (Tunisia)

Spectral aerosol optical thickness have been measured at Thala site (central West of Tunisia) from March to October 2001. The measurement site is located in a continental and non industrialized region, approximately 150 km from the North coast of the Mediterranean Sea and nearby the Algerian border. Thala site could be then influenced by the dust content of the continental air masses carried by western and southern winds. A second pollution source is constituted by industrial and/or maritime particles carried by northern and eastern winds. AOT measurements acquired through the ground-based AERONET are analyzed. The diurnal cycle over Thala and two other areas within the network showed various trends and a prevailing pattern of the optical thickness increase by 10–40% during the day. Daily AOT and monthly averaged aerosol optical thickness, Angstrom coefficient and precipitable water vapor are computed and compared with those of other sites. Measured meteorological parameters represent a valuable supplement to the data sets with the sunphotometer measurements. The analysis of the results shows that there is a high correlation between aerosol optical properties (AOT and Angstrom coefficient) and the local weather conditions, essentially wind speed and direction and air specific humidity.