Validation of ACE and OSIRIS ozone and NO2 measurements using ground-based instruments at 80° N

[摘要] The Optical Spectrograph and Infra-Red Imager System (OSIRIS) and theAtmospheric Chemistry Experiment (ACE) have been taking measurements fromspace since 2001 and 2003, respectively. This paper presents intercomparisonsbetween ozone and NO₂ measured by the ACE and OSIRIS satelliteinstruments and by ground-based instruments at the Polar EnvironmentAtmospheric Research Laboratory (PEARL), which is located at Eureka, Canada(80° N, 86° W) and is operated by the Canadian Network forthe Detection of Atmospheric Change (CANDAC). The ground-based instrumentsincluded in this study are four zenith-sky differential optical absorptionspectroscopy (DOAS) instruments, one Bruker Fourier transform infraredspectrometer (FTIR) and four Brewer spectrophotometers. Ozone total columnsmeasured by the DOAS instruments were retrieved using new Network for theDetection of Atmospheric Composition Change (NDACC) guidelines and agree towithin 3.2%. The DOAS ozone columns agree with the Brewerspectrophotometers with mean relative differences that are smaller than1.5%. This suggests that for these instruments the new NDACC dataguidelines were successful in producing a homogenous and accurate ozonedataset at 80° N. Satellite 14–52 km ozone and 17–40 km NO₂partial columns within 500 km of PEARL were calculated for ACE-FTS Version2.2 (v2.2) plus updates, ACE-FTS v3.0, ACE-MAESTRO (Measurements of AerosolExtinction in the Stratosphere and Troposphere Retrieved by Occultation) v1.2and OSIRIS SaskMART v5.0x ozone and Optimal Estimation v3.0 NO₂ dataproducts. The new ACE-FTS v3.0 and the validated ACE-FTS v2.2 partial columnsare nearly identical, with mean relative differences of 0.0 ± 0.2%and −0.2 ± 0.1% for v2.2 minusv3.0 ozone and NO₂, respectively. Ozonecolumns were constructed from 14–52 km satellite and 0–14 km ozonesondepartial columns and compared with the ground-based total column measurements.The satellite-plus-sonde measurements agree with the ground-based ozone totalcolumns with mean relative differences of 0.1–7.3%. For NO₂, partialcolumns from 17 km upward were scaled to noon using a photochemical model.Mean relative differences between OSIRIS, ACE-FTS and ground-basedNO₂ measurements do not exceed 20%. ACE-MAESTRO measures moreNO₂ than the other instruments, with mean relative differences of25–52%. Seasonal variation in the differences betweenNO₂ partial columns isobserved, suggesting that there are systematic errors in the measurementsand/or the photochemical model corrections. Forozone spring-time measurements, additional coincidence criteria based onstratospheric temperature and the location of the polar vortex were found toimprove agreement between some of the instruments. For ACE-FTS v2.2 minusBruker FTIR, the 2007–2009 spring-time mean relative difference improvedfrom −5.0 ± 0.4% to −3.1 ± 0.8% with the dynamicalselection criteria. This was the largest improvement, likely because bothinstruments measure direct sunlight and therefore have well-characterizedlines-of-sight compared with scattered sunlight measurements. For NO₂,the addition of a ±1° latitude coincidence criterion improvedspring-time intercomparison results, likely due to the sharp latitudinalgradient of NO₂ during polar sunrise. The differences between satelliteand ground-based measurements do not show any obvious trends over themissions, indicating that both the ACE and OSIRIS instruments continue toperform well.

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