OMI/Aura UV product validation using NILU-UV ground-based measurements in Thessaloniki, Greece

摘要: Abstract The main aim of this work is to evaluate the NASA EOS AURA Ozone Monitoring Instrument (OMI) UV irradiance estimates through ground-based measurements performed by a NILU-UV multichannel radiometer (NILU-UV) operating in Thessaloniki, Greece, for time period between January 2005 and December 2014. multi-filter radiometers can provide at 5 wavelength bands with full width half maximum (FWHM) 10 nm approximately analysis 1 min. An additional channel measuring Photosynthetically Active Radiation (PAR) also incorporated instrument used stringent characterization cloud free instances. OMI solar irradiances four wavelengths close those Thessaloniki. Clear all-sky overpass-time, as well local-noon time, are provided Aura Data Validation Center. Spectra measured from collocated MKIII Brewer spectrophotometer serial number 086 (Brewer #086) were utilized whole (2005–2014) order estimate therefore direct comparison validation NILU OMI. For nominal comparisons, using un-flagged data within 50 km radius linear determination coefficient, R2, ranges 0.91 0.97 305 nm 0.75 0.92 380 nm depending on choice overpass or cloudiness flags. best agreement found clear-sky overpass-time comparisons both PAR- satellite algorithm-deduced all wavelengths. overestimate observations Thessaloniki ∼4.5% 13.5% ∼1.5% ∼10.0% 310 nm [overpass vs local noon] restrictions [only satellite-deduced satellite-deduced]. 324 nm wavelengths, clear skies show under-estimation −3.75% −4.15% respectively whereas range −1.55% −1.90% same When imposing PAR-deduced assessment well, over-estimation 2.50% 2.75% 3.70% 4.10% cases effect stricter collocation selection (10 km 25 km 50 km) appears have negligible impact however results smaller statistical sample. flagging applied quality indicators data, amount co-locations decreases appreciatively but correlations improve most (R2 > 0.9 wavelengths). temporal averaging window measurements, around 10 60 min was investigated. differences span result more obvious improvement cases; R2 factor improves 0.94, 0.90, 0.87 0.85 original 0.91, 0.87, 0.82 0.78 0.96, 0.93, 0.80 0.83 305 nm, 310 nm, respectively. Hence, it shown that type implicitly compensate changes position optical properties when comparing ground space. detection seasonal characteristics be safely studied. standard deviation strict ±12% may form dependable measure seasonality imposed retrieval algorithm assumptions. Additionally, aerosol load 340 nm possible zenith angle (SZA) considered. No marked dependence ratio satellite-to-ground remaining 1.1 ± 1.3 1 ± 0.1 while SZA becomes appreciable only angles higher than 70° ratios 1.1 ± 1.0 all-skies 1.0 ± 0.1 below threshold.