Continuous data of the atmosphere monitored using a portable automated lidar are correlated with the concentration of ground-measured suspended particulate matter (SPM). When the boundary layer is well mixed, a high correlation is found between the lidar and the ground SPM data, making it possible to calculate the mass extinction efficiency of the aerosols in the atmosphere. It is found that within the ground layer, the value of mean mass extinction efficiency changes in a range of 4-12 m(2) g(-1), with smaller and larger values occurring for size distributions dominated by coarse and fine particles, respectively. (c) 2004 Elsevier Ltd. All rights reserved.