SAHARAN DUST OUTBREAKS TOWARDS EUROPE: 3 YEARS OF SYSTEMATIC OBSERVATIONS BY THE EUROPEAN LIDAR NETWORK IN THE FRAME OF THE EARLINET PROJECT (2000-2003)

摘要

During a three-year period (2000-2003) 90 Saharan dust outbreaks over Europe were monitored by a coordinated aerosol lidar Network in the frame of the EARLINET project. Multiple aerosol layers of variable thickness (200-2500 m) were systematically observed in the altitude region 1.5-8 km height asl., while traces of dust particles reached heights of 8-10 km, after a 2-5 days transport from the source region. Aerosol optical depths, depolarization ratios and extinction-to-backscatter ratios (lidar ratios) of aerosols ranged from 0.3-0.8 (at 355 nm or 351 nm), 10 to 25 % and 35 to 80 sr, respectively, within the lofted dust plumes. Air mass back-trajectory analysis and model calculations from the DREAM model, in conjunction with satellite data analysis (MODIS, TOMS, SeaWiFS), related the measurements during these dust events to the Saharan region. The vertical and horizontal extent of these outbreaks is discussed and their seasonal distribution is given.