Abstract
Multi-wavelength aerosol Raman lidar measurements with elastic depolarization at 532 nm were combined with sun photometry during the HYGRA-CD campaign over Athens, Greece, on May-June 2014. We retrieved the aerosol optical [3 aerosol backscatter profiles (baer ) at 355-532-1064 nm, 2 aerosol extinction (aaer ) profiles at 355-532 nm and the aerosol linear depolarization ratio (δ ) at 532 nm] and microphysical properties [effective radius (reff ), complex refractive index (m ), single scattering albedo (ω )]. We present a case study of a long distance transport (~3.500-4.000 km) of biomass burning particles mixed with dust from the Russian Federation-Kazakhstan regions arriving over Athens on 21-23 May 2014 (1.7-3.5 km height). On 23 May, between 2-2.75 km we measured mean lidar ratios (LR) of 35 sr (355 nm) and 42 sr (532 nm), while the mean Angstrom exponent (AE) aerosol backscatter-related values (355nm/532nm and 532nm/1064nm) were 2.05 and 1.22, respectively; the mean value of δ at 532 nm was measured to be 9%. For that day the retrieved mean aerosol microphysical properties at 2-2.75 km height were: reff =0.26 μm (fine mode), reff =2.15 μm (coarse mode), m =1.36+0.00024i, ω =0.999 (355 nm, fine mode), ω =0.992(355 nm, coarse mode), ω =0.997 (532 nm, fine mode), and ω =0.980 (532 nm, coarse mode).
Highlights
The HygrA-CD campaign was an international field campaign which took place in Athens, Greece between 15 May and 22 June 2014, within the Initial Training on Atmospheric Remote Sensing-ITARS project
Despite recent progress documented in the latest Intergovernmental Panel for Climate Change (IPCC) [1], the uncertainty about the current level of radiative forcing due to aerosols (0.5 Wm-2) is still relatively large compared to that of global warming gases (0.25 Wm-2)
EOLE and AIAS are based in the Laser Remote Sensing Unit (LRSU) of the National Technical University of Athens (NTUA) (37.9oN, 23.6oE, 200 m a.s.l.)
Summary
The HygrA-CD campaign was an international field campaign which took place in Athens, Greece between 15 May and 22 June 2014, within the Initial Training on Atmospheric Remote Sensing-ITARS project (www.itars.net). HYGRA -CD (http://hygracd.impworks.gr) brought together a suite of different instruments and expertise aiming to enhance our understanding on the impact of aerosols and clouds on weather and climate. It was based on the synergy between remote sensing and in-situ instrumentation, making use of numerical weather prediction and atmospheric modeling. In order to clarify the mechanisms of aerosol radiative forcing and reduce the respective uncertainties, detailed knowledge of the vertical profiles of the particle optical (baer, aaer, AE and LR) together with microphysical (reff, m, ω) and chemical properties (water content, dry chemical composition), as well as their mass concentration are required [1,2,3]. Raman lidars have proven to be the most adapted tools in aerosol characterization experiments since they can provide the vertical profiles of baer and aaer with very high spatial and temporal resolution [3 and references therein]
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