Abstract
Elastic lidar signals at 355, 532, and 1064 nm combined with aerosol optical thicknesses (AOTs) from sunphotometer measurements collocated in space and time have been used to retrieve columnar lidar ratio (LR) values at the lidar wavelengths by a constrained iterative inversion procedure. Then, the relationships of LRs with AOTs, Angstrom exponents, fine mode fractions ( η ), and fine mode radii ( Rf ) have been investigated for the aerosol typing. η and R f values have been retrieved from a graphical framework. It is shown that the implemented methodology has allowed identifying three main aerosol types over the Central Mediterranean which are designed as urban/industrial, marine-polluted, and mixed-dust. Results on the relationships of LRs with AOTs, A, η , and R f for each aerosol type represent main paper results.
Highlights
The impact of aerosol on climate is widely recognized and several efforts have been undertaken to characterize aerosol optical and microphysical properties and estimate aerosol direct and indirect radiative effects
A case study is analyzed, as an example, to demonstrate the ability of the constrained iterative inversion (CII)-graphical framework (GF) technique on estimating the dependence on altitude of the fine mode aerosol contribution and the fine mode aerosol radius, on the basis of the Å and ΔÅ profiles retrieved from lidar measurements
aerosol optical thicknesses (AOTs) are in accordance within 0.1 with the corresponding values retrieved from the AERONET (Lecce University) sunphotometer measurements at 1332 UTC
Summary
The impact of aerosol on climate is widely recognized and several efforts have been undertaken to characterize aerosol optical and microphysical properties and estimate aerosol direct and indirect radiative effects. The sensitivity of aerosol direct radiative effects and heating rates (HRs) to the vertical distribution of aerosol properties has recently been investigated by one of the authors [1]. Lidars are days the best tools that can allow retrieving the vertical distribution of the aerosol properties. Numerical procedures only based on elastic lidar signals have been developed to characterize the dependence on altitude of aerosol properties. A numerical tool (LIRIC, LIdar/Radiometer Inversion Code) to retrieve vertically resolved aerosol microphysical properties by combining backscatter coefficient measurements at 3 wavelengths and sun/sky radiance measurements is described in [3]. In this study the CII-GF retrieval scheme is applied to lidar measurements performed at a coastal site of southeastern Italy with the main goal of contributing to the typing of the Central Mediterranean aerosol.
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