Atmos. Chem. Phys. Discuss., 13, 18535-18579, 2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Vertically resolved aerosol properties by multi wavelengths lidar measurements
M. R. Perrone1, F. De Tomasi1, and G. P. Gobbi2
1Matematical and Physical Department, Universita' del Salento, 73100 Lecce, Italy
2Institute of Atmospheric Sciences and Climate, CNR, Rome, Italy

Abstract. A new approach is introduced to characterize the dependence on altitude of the aerosol fine mode radius (Rf) and of the fine mode contribution (η) to the aerosol optical thickness (AOT) by three-wavelength lidar measurements. The introduced approach is based on the graphical method of Gobbi et al. (2007), which was applied to AERONET spectral extinction observations and relies on the combined analysis of the Ångstrom exponent (å) and its spectral curvature Δå. Lidar measurements at 355, 532 and 1064 nm were used in this study to retrieve the vertical profiles of å and Δå and to determine the dependence on altitude of Rf and η (532 nm) from the å–Δå combined analysis. Lidar measurements were performed at the Mathematics and Physics Department of Universita' del Salento, in south eastern Italy. Aerosol from continental Europe, the Atlantic, northern Africa, and the Mediterranean Sea are often advected over south eastern Italy and as a consequence, mixed advection patterns leading to aerosol properties varying with altitude are dominant. The proposed approach was applied to eleven measurement days to demonstrate its feasibility in different aerosol load conditions. The selected-days were characterized by AOTs spanning the 0.23–0.67, 0.15–0.41, and 0.04–0.25 range at 355, 532, and 1064 nm, respectively. Lidar ratios varied within the 28–80, 30–70, and 30–55 sr range at 355, 532, and 1064 nm, respectively, for the high variability of the aerosol optical and microphysical properties. å(355 nm, 1064 nm) values retrieved from lidar measurements ranged between 0.12 and 2.5 with mean value ±1 standard deviation equal to 1.4 ± 0.5. Δå varied within the −0.10–0.87 range with mean value equal to 0.1 ± 0.4. Rf and η (532 nm) values spanning the 0.02–0.30 μm and the 0.30–0.99 range, respectively were associated to the å–Δå data points. Rf and η values showed no dependence on the altitude. 72% of the data points were in the Δå–å space delimited by the η and Rf curves varying within 0.70–0.95 and 0.15–0.05 μm, respectively for the dominance of fine mode particles in driving the AOT over south eastern Italy. Volume depolarization vertical profiles retrieved from lidar measurements, aerosol products from AERONET sunphotometer measurements collocated in space and time, the BSC-DREAM model, analytical back trajectories, and satellite images were used to demonstrate the robustness of the proposed method.

Citation: Perrone, M. R., De Tomasi, F., and Gobbi, G. P.: Vertically resolved aerosol properties by multi wavelengths lidar measurements, Atmos. Chem. Phys. Discuss., 13, 18535-18579, doi:10.5194/acpd-13-18535-2013, 2013.
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