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Aerosol optical depth comparison between GAW-PFR and AERONET-Cimel radiometers from long-term (2005–2015) 1 min synchronous measurements
Title: Aerosol optical depth comparison between GAW-PFR and AERONET-Cimel radiometers from long-term (2005–2015) 1 min synchronous measurements
Authors: Cuevas Agulló, EmilioRomero Campos, Pedro MiguelKouremeti, NataliaKazadzis, SteliosRäisänen, PetriGarcía Cabrera, Rosa DeliaBarreto Velasco, ÁfricaGuirado-Fuentes, CarmenRamos López, RamónToledano, CarlosAlmansa Rodríguez, Antonio FernandoGröbner, Julian
Keywords: Aerosol optical depth; Radiometers; Global Atmosphere Watch; AERONET-Cimel; Aerosol measurement
Issue Date: 2019
Publisher: European Geosciences Union
Citation: Atmospheric Measurement Techniques. 2019, 12(8), p. 4309–4337
Publisher version:
Abstract: A comprehensive comparison of more than 70 000 synchronous 1 min aerosol optical depth (AOD) data from three Global Atmosphere Watch precision-filter radiometers (GAW-PFR), traceable to the World AOD reference, and 15 Aerosol Robotic Network Cimel radiometers (AERONET-Cimel), calibrated individually with the Langley plot technique, was performed for four common or “near” wavelengths, 380, 440, 500 and 870 nm, in the period 2005–2015. The goal of this study is to assess whether, despite the marked technical differences between both networks (AERONET, GAW-PFR) and the number of instruments used, their long-term AOD data are comparable and consistent. The percentage of data meeting the World Meteorological Organization (WMO) traceability requirements (95 % of the AOD differences of an instrument compared to the WMO standards lie within specific limits) is >92 % at 380 nm, >95 % at 440 nm and 500 nm, and 98 % at 870 nm, with the results being quite similar for both AERONET version 2 (V2) and version 3 (V3). For the data outside these limits, the contribution of calibration and differences in the calculation of the optical depth contribution due to Rayleigh scattering and O3 and NO2absorption have a negligible impact. For AOD >0.1, a small but non-negligible percentage (∼1.9 %) of the AOD data outside the WMO limits at 380 nm can be partly assigned to the impact of dust aerosol forward scattering on the AOD calculation due to the different field of view of the instruments. Due to this effect the GAW-PFR provides AOD values, which are ∼3 % lower at 380 nm and ∼2 % lower at 500 nm compared with AERONET-Cimel. The comparison of the Ångström exponent (AE) shows that under non-pristine conditions (AOD >0.03 and AE <1) the AE differences remain <0.1. This long-term comparison shows an excellent traceability of AERONET-Cimel AOD with the World AOD reference at 440, 500 and 870 nm channels and a fairly good agreement at 380 nm, although AOD should be improved in the UV range.
Sponsorship : The Federal Office of Meteorology and Climatology MeteoSwiss International Affairs Division, Swiss GCOS Office, has funded the project “The Global Atmosphere Watch Precision Filter Radiometer (GAW-PFR) Network for Aerosol Optical Depth long term measurements”, and specifically the GAW-PFR program at the Izaña Observatory. AEMET has funded the AERONET programme at the Izaña Observatory. Some of the AERONET-Cimel radiometers have been calibrated at Izaña Observatory by the AERONET Europe Calibration Service, financed by specific European Community programmes for integrating activities: Research Infrastructure Action under the Seventh Framework Programme (grant no. FP7/2007-2013) and ACTRIS (grant no. 45 262254). This research has received funding from the European Union's Horizon 2020 Research and Innovation Programme (grant no. 654109) (ACTRIS-2). Funding from MINECO (grant no. CTM2015-66742-R) and Junta de Castilla y León (grant no. VA100P17) is also gratefully acknowledged. Much of this study has been performed in the frame of the WMO CIMO Izaña test bed for aerosols and water vapour remote-sensing instruments funded by AEMET.
ISSN: 1867-1381
Appears in Collections:Artículos científicos 2019-2022

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