Seasonal variability of aerosol optical properties observed by means of an elastic-Raman lidar over Northeastern Spain.

Abstract

The annual and seasonal variability of aerosol optical properties observed by means of an elastic-Raman lidar over Northeastern Spain has been assessed. The lidar representativeness has first been checked against sun-photometer measurements in terms of aerosol optical thickness. Then the annual cycle and the seasonal variability of the planetary boundary layer aerosol optical thickness and its fraction compared to the columnar optical thickness, the lidar ratio, the backscatter-related Ångström exponent and the planetary boundary layer height have been analyzed and discussed. Winter and summer mean profiles of extinction, backscatter and lidar ratio retrieved with the Raman algorithm have been presented. The analysis shows the impact of most of the natural events (Saharan dust intrusions, wildfires, etc.) and meteorological situations (summer anticyclonic situation, the formation of the Iberian thermal low, winter long-range transport from North Europe and/or North America, re-circulation flows, etc.) occurring in the Barcelona area. A detail study of a special event including a combined intrusion of Saharan dust and biomass-burning particles has proven the suitability of combining nighttime Raman- and daytime pure elastic-inversions to discriminate spatially different types of aerosols and to follow their spatial and temporal evolution.