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Proceedings Paper

Aerosol extinction and absorption in Évora, Portugal, during the European 2003 summer heat wave
Author(s): Thierry Ghislain Elias; Ana Maria Silva; Maria João Figueira; Nuno Belo; Sergio Pereira; Paola Formenti; Gunter Helas
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Paper Abstract

Aerosol optical properties are retrieved from measurements acquired during the 2003 summer at the new AERONET station of Evora, Portugal, with a sun/sky photometer, a fluxmeter and a nephelometer. Aerosol optical thickness (aot) derived at several wavelengths shows that an exceptionally long turbid event occurred in July-August. Desert dust particles transported from North Africa increased aot at 873 nm (aot873) to the value of 0.27 with an Ångstrom exponent αC=0.5. Emissions from forest fires in The Iberic peninsula affected Evora since the end of the dust episode, with aot441 reaching 0.81 and aC=1.8. The aerosol scattering coefficient measured at surface level shows that desert dust does not reach the surface level at Evora while the forest fire emissions were uniformly distributed over the atmospheric column. Sky-radiance and flux measurements agree in retrieval of the aerosol single scattering albedo (assa) at several wavelengths. A large absorption rate is found with a high spectral dependence for desert dust particles (assa441=0.86 and ass873=0.93) and with a flat spectral dependence during the forest fires emission episode (assa441=0.88 and assa873=0.87). All measurements as well as back-trajectory calculations indicate mixture of particles during the desert dust.

Paper Details

Date Published: 30 November 2004
PDF: 12 pages
Proc. SPIE 5571, Remote Sensing of Clouds and the Atmosphere IX, (30 November 2004); doi: 10.1117/12.566579
Show Author Affiliations
Thierry Ghislain Elias, Ctr. de Geofisica de Evora (Portugal)
Ana Maria Silva, Ctr. de Geofisica de Evora (Portugal)
Maria João Figueira, Ctr. de Geofisica de Evora (Portugal)
Nuno Belo, Ctr. de Geofisica de Evora (Portugal)
Sergio Pereira, Ctr. de Geofisica de Evora (Portugal)
Paola Formenti, Lab. Interuniversitaire des Systemes Atmospheriques (France)
Gunter Helas, Max-Planck-Institut für Chemie (Germany)

Published in SPIE Proceedings Vol. 5571:
Remote Sensing of Clouds and the Atmosphere IX
Adolfo Comeron; Michel R. Carleer; Richard H. Picard; Nicolaos I. Sifakis, Editor(s)

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