Raman lidar-derived aerosol optical properties and classification during the FENNEC experiment – Coherence with CAMS data

Abstract. As part of the FENNEC programme, a field campaign was conducted on the Mediterranean coast of southern Spain, close to Gibraltar, from June to August 2011. Using a relatively straightforward ground-based N₂–Raman lidar, several aerosol optical properties were retrieved at 355 nm, including the linear particle depolarisation ratio (PDR), the lidar ratio (LR), and the aerosol backscatter and extinction coefficients. Of the 58 sampled nights, several periods were identified in which aerosol events exhibited optical thicknesses greater than 0.5.  The primary causative agents of these events are the influx of Saharan dust mixed with local polluted and marine air masses. Pairing PDR and LR has been shown to be significant in identifying three distinct bulk aerosol classes: dust, carbonaceous and soluble (predominantly marine) aerosols. After processing the night-time data to ensure sufficient lidar range, the study demonstrates the efficiency of lidar profiles in evaluating the reliability of the Copernicus Atmosphere Monitoring Service (CAMS) reanalyses of atmospheric aerosols up to approximately 7 km above mean sea level (a.m.s.l.). The two datasets show excellent consistency in terms of the optical thickness and vertical profile of the aerosol extinction coefficient in the Saharan dust aerosol layers. CAMS reproduces the temporal evolution well, with a correlation coefficient (COR) greater than 0.8. However, this is less true for the layer below 2 km a.m.s.l. (COR = 0.56), where there is a tendency for CAMS to underestimate compared to ground-based lidar.