Height and seasonal dependence of aerosol optical properties over southeast Italy

摘要

Systematic Raman lidar measurements performed from May 2000 to August 2002 in the framework of the European Aerosol Research Lidar Network are analyzed and discussed. Main results on height dependence and seasonal cycle of extinction α(z) and backscatter β(z) coefficients, aerosol optical depths AOD(z), and lidar ratios S(z) are presented. Yearly-averaged vertical profiles of extinction and backscatter coefficients reveal that both α(z) and β(z) decrease more than 75% within the lowermost 2 km. Yearly-averaged lidar ratios increase from about 42–48 sr in the lowermost 2 km to between 67–72 sr in the air masses above 2 km. The changes in lidar ratios are indicative of changes in the physical characteristics of the monitored aerosols and suggest that over the monitoring site, the lowermost air masses (z 2 km) are characterized by lidar ratios typical of continental aerosol type. The seasonal cycle analysis reveals that the average maximum height zM at which aerosols are detected by the lidar that is about 5 km in spring-summer, and decreases up to about 3 km in autumn-winter.