title: Determination of ultraviolet cosine-corrected irradiances and aerosol optical thickness by combined measurements with a Brewer spectrophotometer and a multifilter rotating shadowband radiometer.
abstract: Combined measurements of diffuse-to-global radiation ratio and global spectral irradiances in the UV are used to derive cosine-corrected UV irradiances and aerosol optical depth (AOD). The diffuse-to-global radiation ratio is used first in the cosine correction of the global irradiance, then to calculate absolutely calibrated direct irradiances. The Beer-Lambert law is applied to derive the UV AOD using independent measurements of the extraterrestrial solar flux. The AOD can be derived with an uncertainty of about 0.03 at 60 degrees solar zenith angle. The method was applied to measurements obtained with two UV multifilter rotating shadowband radiometers (UV-MFRSRs) and a MK III Brewer spectrophotometer on the Island of Lampedusa in the Central Mediterranean during two periods of 2002 and 2004. The derived AOD at 318 and 332 nm was compared with UV AOD measured at 318, 320, and 368 nm with different techniques. The retrieved AOD, combining MFRSR and Brewer measurements, is in good agreement with the optical depth derived with the other methods.
authors.affiliation: ENEA-ACS, Via Anguillarese 301, 00123 S Maria di Galeria, Italy. disarra@casaccia.enea.it
authors.forename: Alcide
authors.initials: A
authors.lastname: di Sarra
authors.forename: Daniele
authors.initials: D
authors.lastname: Fua
authors.forename: Marco
authors.initials: M
authors.lastname: Cacciani
authors.forename: Tatiana
authors.initials: T
authors.lastname: Di Iorio
authors.forename: Patrick
authors.initials: P
authors.lastname: Disterhoft
authors.forename: Daniela
authors.initials: D
authors.lastname: Meloni
authors.forename: Francesco
authors.initials: F
authors.lastname: Monteleone
authors.forename: Salvatore
authors.initials: S
authors.lastname: Piacentino
authors.forename: Damiano
authors.initials: D
authors.lastname: Sferlazzo