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Advanced characterisation of aerosol size properties from measurements of spectral optical depth using the GRASP algorithm
Title: Advanced characterisation of aerosol size properties from measurements of spectral optical depth using the GRASP algorithm
Authors: Torres, BenjamínDubovik, OlegFuertes Marrón, DavidSchuster, GregoryCachorro, Victoria E.Lapyonok, TatsianaGoloub, PhilippeBlarel, LucBarreto Velasco, África ORCID RESEARCHERID SCOPUSID Autor AEMETMallet, MarcToledano, CarlosTanré, Didier
Keywords: Aerosol properties; AERONET; Spectral optical depth
Issue Date: 2017
Publisher: European Geosciences Union
Citation: Atmospheric Measurement Techniques. 2017, 10(10), p. 3743–3781
Publisher version:
Abstract: This study evaluates the potential of using aerosol optical depth (τa) measurements to characterise the microphysical and optical properties of atmospheric aerosols. With this aim, we used the recently developed GRASP (Generalized Retrieval of Aerosol and Surface Properties) code for numerical testing of six different aerosol models with different aerosol loads. The direct numerical simulations (self-consistency tests) indicate that the GRASP-AOD retrieval provides modal aerosol optical depths (fine and coarse) to within 0.01 of the input values. The retrieval of the fine-mode radius, width and volume concentration are stable and precise if the real part of the refractive index is known. The coarse-mode properties are less accurate, but they are significantly improved when additional a priori information is available. The tests with random simulated errors show that the uncertainty in the bimodal log-normal size distribution parameters increases as the aerosol load decreases. Similarly, the reduction in the spectral range diminishes the stability of the retrieved parameters. In addition to these numerical studies, we used optical depth observations at eight AERONET locations to validate our results with the standard AERONET inversion products. We found that bimodal log-normal size distributions serve as useful input assumptions, especially when the measurements have inadequate spectral coverage and/or limited accuracy, such as moon photometry. Comparisons of the mode median radii between GRASP-AOD and AERONET indicate average differences of 0.013 µm for the fine mode and typical values of 0.2–0.3 µm for the coarse mode. The dominant mode (i.e. fine or coarse) indicates a 10 % difference in mode radii between the GRASP-AOD and AERONET inversions, and the average of the difference in volume concentration is around 17 % for both modes. The retrieved values of the fine-mode τa(500) using GRASP-AOD are generally between those values obtained by the standard AERONET inversion and the values obtained by the AERONET spectral deconvolution algorithm (SDA), with differences typically lower than 0.02 between GRASP-AOD and both algorithms. Finally, we present some examples of application of GRASP-AOD inversion using moon photometry and the airborne PLASMA sun photometer during the ChArMEx summer 2013 campaign in the western Mediterranean.
Sponsorship : The research has been supported by the Labex CaPPA: the CaPPA project (Chemical and Physical Properties of the Atmosphere) is funded by the French National Research Agency (ANR) through the PIA (Programme d’Investissement d’Avenir) under contract “ANR-11-LABX-0005-01” and by the Regional Council “Nord Pas de Calais – Picardie” and the European Funds for Regional Economic Development (FEDER). Acknowledgements are addressed to ESA/ESRIN for funding through the IDEAS+ (Instrument Data quality Evaluation and Analysis Service) contract. This research has also received funding from the French National Research Agency (ANR) project ADRIMED (contract ANR-11-BS56-0006). This work is part of the ChArMEx project supported by ADEME, CEA, CNRS-INSU and Météo- France through the multidisciplinary programme MISTRALS (Mediterranean Integrated Studies aT Regional And Local Scales). The authors acknowledge the funding provided by the European Union (H2020-INFRAIA-2014-2015) under grant agreement no. 654109 (ACTRIS-2). Financial support was also provided by the Spanish MINECO (CTM2015-66742-R).
ISSN: 1867-1381
Appears in Collections:Artículos científicos 2015-2018

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