Abstract
Abstract. Four years (2010–2013) of observations with polarization lidar and sun/sky photometer at the combined European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) site of Limassol (34.7° N, 33° E), Cyprus, were used to compare extinction-to-backscatter ratios (lidar ratios) for desert dust from Middle East deserts and the Sahara. In an earlier article, we analyzed one case only and found comparably low lidar ratios < 40 sr for Middle East dust. The complex data analysis scheme is presented. The quality of the retrieval is checked within a case study by comparing the results with respective Raman lidar solutions for particle backscatter, extinction, and lidar ratio. The applied combined lidar/photometer retrievals corroborate recent findings regarding the difference between Middle East and Saharan dust lidar ratios. We found values from 43–65 sr with a mean (±standard deviation) of 53 ± 6 sr for Saharan dust and from 33–48 sr with a mean of 41 ± 4 sr for Middle East dust for the wavelength of 532 nm. The presented data analysis, however, also demonstrates the difficulties in identifying the optical properties of dust even during outbreak situations in the presence of complex aerosol mixtures of desert dust, marine particles, fire smoke, and anthropogenic haze.
Highlights
The particle extinction-to-backscatter ratio or lidar ratio S is an important quantity in the description of atmospheric aerosols with lidar (Müller et al, 2007; Burton et al, 2012; Groß et al, 2013) and a key input parameter in the retrieval of vertical profiles of the particle extinction coefficient from measurements with elastic backscatter lidars (Fernald, 1984; Ansmann, 2006) such as the spaceborne Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) (Omar et al, 2009)
During a few major dust outbreaks, the Raman lidar method (Mattis et al, 2002) could be applied so that desert-dust lidar ratios could directly be determined in the dense dust layers, in which the particle depolarization ratio showed values around 0.3 at 532 nm
The particle lidar ratio is an important quantity in the description of atmospheric aerosols and aerosol mixtures in the framework of aerosol typing efforts
Summary
The particle extinction-to-backscatter ratio or lidar ratio S is an important quantity in the description of atmospheric aerosols with lidar (Müller et al, 2007; Burton et al, 2012; Groß et al, 2013) and a key input parameter in the retrieval of vertical profiles of the particle extinction coefficient from measurements with elastic backscatter lidars (Fernald, 1984; Ansmann, 2006) such as the spaceborne Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) (Omar et al, 2009). Present and upcoming spaceborne lidar activities (Stoffelen et al, 2005; Ansmann et al, 2007; Winker et al, 2009; Illingworth et al, 2014) need lidar-ratio information for all relevant aerosol types such as urban haze, biomass burning smoke, desert dust and marine particles in key areas of climate relevance for a consistent interpretation of the space-lidar-derived aerosol and cloud products. As a consequence the real part of the refractive index decreases from 1.55 for Arabian dust
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