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Assessment of Sun photometer Langley calibration at the high-elevation sites Mauna Loa and Izaña [Discussion paper]
Title: Assessment of Sun photometer Langley calibration at the high-elevation sites Mauna Loa and Izaña [Discussion paper]
Authors: Toledano, CarlosGonzález, RamiroFuertes, DavidCuevas Agulló, Emilio ORCID RESEARCHERID SCOPUSID Autor AEMETEck, Thomas F.Kazadzis, SteliosKouremeti, NataliaGröbner, JulianGoloub, PhilippeBlarel, LucRomán, RobertoBarreto, África RESEARCHERID Holben, Brent N.Cachorro, Victoria E.
Keywords: Sun photometer; High-mountain stations; Aerosol optical depth
Issue Date: 2018
Publisher: European Geosciences Union
Citation: Atmospheric Chemistry and Physics Discussions. 2018
Publisher version:
Abstract: The aim of this paper is to analyze the suitability of the high-mountain stations Mauna Loa and Izaña for Langley plot calibration of Sun photometers. Thus the aerosol optical depth (AOD) characteristics and seasonality, as well as the cloudiness, have been investigated in order to provide a robust estimation of the calibration accuracy, as well as the number of days that are suitable for Langley calibrations. The data used for the investigations belong to AERONET and GAW-PFR networks, which maintain reference Sun photometers at these stations with long measurement records: 22 years at Mauna Loa and 15 years at Izaña. In terms of clear sky and stable aerosol conditions, Mauna Loa (3397m a.s.l.) exhibits on average of 377 Langleys (243 morning and 134 afternoon) per year suitable for Langley plot calibration, whereas Izaña (2373m a.s.l.) shows 343 Langleys (187 morning and 155 afternoon) per year. The background AOD (500nm) values, on days that are favorable for Langley calibrations, are in the range 0.01-0.02 throughout the year, with well defined seasonality that exhibits a spring maximum at both stations plus a slight summer increase at Izaña. The statistical analysis of the long-term determination of extraterrestrial signals yields to a calibration uncertainty of ~0.2-0.5%, being this uncertainty smaller in the near infrared and larger in the ultraviolet wavelengths. This is due to atmospheric variability that cannot be reduced based only on quality criteria of individual Langely plots.
Sponsorship : This research has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No 654109 (ACTRIS-2). The funding 10 by MINECO (CTM2015-66742-R) and Junta de Castilla y León (VA100P17) is also acknowledged.
ISSN: 1680-7367
Appears in Collections:Artículos científicos 2015-2018

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