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A VAISALA Ceilometer CL31 is operating continuously in the Observatory of the Evora Geophysics Centre (CGE) since May 2006. The CL31 ceilometer provides measurements of the cloud base height up to three simultaneous layers and of the profile of the backscatter coefficient, which in the absence of clouds gives a good approximation of the qualitative aerosol boundary layer profile. The ceilometer backscatter measurements are used here to study special aerosol events that reach Evora (38 degrees 34'N, 7 degrees 54'W, 300m a.m.s.l.) such as forest fires, desert dust transports originating from the Sahara desert, which often occur in the south of Portugal and European pollution. The aerosol backscatter coefficient corresponding to the lowest layers of the atmosphere is also correlated with mass concentration measurements obtained from a TEOM (Tapered Element Oscillating Microbalance) installed in the same place. (CGE observatory). The TEOM measures the in situ mass concentration of aerosols near the ground, with aerodynamic diameter lower than 10 mu m (PM-10), with temporal sampling of 10min. Furthermore, ceilometer measurements and derived mixing height are also compared with measurements taken with a Lidar during an intensive campaign that took place at the CGE observatory in Evora, during the first half of June 2006.