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Diurnal and nocturnal measurements of aerosol optical depth at a desert site in Namibia (Articolo in rivista)

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Diurnal and nocturnal measurements of aerosol optical depth at a desert site in Namibia (Articolo in rivista) (literal)

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Esposito F. , S. Mari, G. Pavese, C. Serio (2003)
Diurnal and nocturnal measurements of aerosol optical depth at a desert site in Namibia
in Aerosol science and technology (Print)
(literal)

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Nell'ambito del progetto HESS (High Energy Stereoscopic System) sono state effettuate misure radiometriche di irradianza solare e lunare nell'area di Gambsberg in Namibia (Africa), sito candidato per l'installazione di un telescopio per lo studio di radiazione cosmica. In questo contesto se ne è studiata la trasparenza atmosferica. Si è verificato che il sito, benché lontano da aree urbane, può essere influenzato da masse d'aria contenenti cristalli di sale e provenienti sia dall'Atlantico che dalla depressione salina di Makgadikgadi, sita in Botswana. (literal)

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F. Esposito: DIFA Università della Basilicata S. Mari: INFN Sez. di Roma Università della Basilicata G. Pavese: IMAA-CNR C. Serio: DIFA Università della Basilicata (literal)

Titolo

Diurnal and nocturnal measurements of aerosol optical depth at a desert site in Namibia (literal)

Abstract

The Namibian desert is a candidate site for astrophysical observations with ground-based instrumentation, such as the High Energy Stereoscopic System experiment. For this kind of application, the characterization of the atmospheric transmittance is mandatory. In this context, a first campaign of both solar and lunar direct irradiance measurements has been performed from 7 July 1998 to 10 July 1998 on a desert plateau in Namibia. The aerosol optical depth in the visible range (330-700 nm) has been measured; we found daily values (at 483 nm) ranging from 0.10 to 0.26, while the nightly ones range from 2.5 x 10(-3) up to 0.86. By means of a least square fitting procedure, the a Angstrom turbidity parameters have been estimated. (alpha daily values 0.92 divided by 3.64, alpha nightly values 0.008 divided by 4.2; beta daily values 0.06 divided by 0.56, beta nightly values 0.001 divided by 0.68). Furthermore, a relationship between a Angstrom parameters and meteorological variables such as relative humidity and wind speed has been investigated. The results do not highlight any correlation, except for two diurnal data sets that show a negative correlation between the optical thickness and the wind speed. Although preliminary, our measurements allow us to have a first insight into characterizing the aerosol optical properties of the Namibian background aerosol. On the other hand, an extended campaign of measurements is needed for a full characterization of the site. (literal)

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