title: Portable device for characterizing the angular response of UV spectroradiometers.
abstract: This paper introduces a device that was developed to measure the angular response of UV spectroradiometers in the field. This device is designed to be used at the operating position of spectroradiometers; thus the derived angular response also includes any effects from imperfect leveling of the diffuser and corresponds to the actual operational angular response. The design and characterization of the device and the results from its application on 11 different spectroradiometers that operate at different European UV stations are presented. Various sources of uncertainties that were identified result in a combined uncertainty in determining the angular response, which ranges between approximately 1.5% and 10%, depending on the incidence angle and the characteristics of the diffuser. For the 11 instruments, the error in reporting the diffuse irradiance ranges between 2% and - 13%, assuming isotropic distribution of the downwelling radiances.
authors.affiliation: Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Campus Box 149, 54124 Thessaloniki, Greece.
authors.forename: Alkiviadis F
authors.initials: AF
authors.lastname: Bais
authors.forename: Stylianos
authors.initials: S
authors.lastname: Kazadzis
authors.forename: Katerina
authors.initials: K
authors.lastname: Garane
authors.forename: Natalia
authors.initials: N
authors.lastname: Kouremeti
authors.forename: Julian
authors.initials: J
authors.lastname: Gröbner
authors.forename: Mario
authors.initials: M
authors.lastname: Blumthaler
authors.forename: Gunther
authors.initials: G
authors.lastname: Seckmeyer
authors.forename: Ann R
authors.initials: AR
authors.lastname: Webb
authors.forename: Tapani
authors.initials: T
authors.lastname: Koskela
authors.forename: Peter
authors.initials: P
authors.lastname: Görts
authors.forename: Josef
authors.initials: J
authors.lastname: Schreder