Altitude-resolved properties of a Saharan dust event over the Mediterranean

Abstract

Some insight is provided about the time and altitude evolution of a Saharan dust event observed by lidar during the spring 1999 EU campaign PAUR-II at Crete (35°N–23°E). The dust episode lasted approximately eight days, reaching maximum optical depth τ≈0.6, at 532 nm. Clear tropospheric conditions ( τ≈0.1) preceded and followed the event. Maritime aerosols, mixed phase clouds and cirrus-generating particles were also observed during the campaign. An altitude-resolved description of lidar-derived backscatter and depolarization of observed aerosols and clouds is provided. The nature and phase of the particles is inferred on the basis of these variables. Particles extinction and surface area are estimated on the basis of an aerosol model. The data analysis shows how Saharan dust events can reach and persist in the 10 km altitude region, overturning the vertical structure of the tropospheric aerosol optical depth. The analysis will also show that both aerosols and clouds mainly existed as mixed phases of solid and liquid particles.