Desert dust transported over Europe: Lidar observations and model evaluation of the radiative impact

Three years of measurements of aerosol vertical profiles (2007–2009) made at the lidar station of L'Aquila, a site in central Italy that is part of the European Aerosol Research Lidar Network, are studied by means of well‐tested radiative transfer models to analyze the radiative impact of miner...

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Bibliographic Details
Published in:Journal of geophysical research. Atmospheres 2015-04, Vol.120 (7), p.2881-2898
Main Authors: Pitari, Giovanni, Di Genova, Glauco, Coppari, Eleonora, De Luca, Natalia, Di Carlo, Piero, Iarlori, Marco, Rizi, Vincenzo
Format: Article
Language:English
Subjects:
Aerosols
Albedo
Atmospheric aerosols
Coarsening
Desert dust
Deserts
Dust
Extinction
Geophysics
Lidar
Mathematical models
Radiation
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Summary:Three years of measurements of aerosol vertical profiles (2007–2009) made at the lidar station of L'Aquila, a site in central Italy that is part of the European Aerosol Research Lidar Network, are studied by means of well‐tested radiative transfer models to analyze the radiative impact of mineral dust aerosols transported from the Sahara desert. Sixteen major episodes of desert dust transport are considered; the radiative analysis is conducted in terms of diurnal averages of the top‐of‐atmosphere radiative flux changes (TOARFC) with respect to a reference “clean” aerosol profile not perturbed by long‐range transported desert particles. The aerosol size distribution, needed as an input parameter for the Mie scattering program to obtain single‐scattering albedo, asymmetry parameter, and extinction scaling over the whole wavelength spectrum, is obtained from simultaneous surface measurements with a multichannel aerosol spectrometer. The calculated average net TOARFC is +2.3 and +3.0 W/m2 in clear‐ and total‐sky conditions, respectively. Solar, planetary components account for −0.42 and +2.7 W/m2 in clear‐sky conditions and +0.93 and +2.1 W/m2 in total‐sky conditions, respectively. The large effective radius of these coarse mode soil dust particles (reff = 1.5 µm) makes the longwave planetary component of the TOARFC dominant over the solar component, at least for typical continental surface albedo values (0.18 on average, at L'Aquila). The solar component, however, shows a pronounced sensitivity to the surface albedo and becomes dominant over the longwave component for both an ocean albedo (0.07) and a typical surface‐snow albedo (0.4), with TOARFC values of −6.3 and +10.6 W/m2, respectively. Key Points Desert dust significantly affects the radiative balance in remote regions Lidar measurements allow a good vertical discrimination of aerosol extinction On land albedo, the planetary radiative perturbation is larger than the solar
ISSN:2169-897X
2169-8996
DOI:10.1002/2014JD022875