An intercomparison of ground‐based UV‐visible sensors of ozone and NO₂

Abstract

Abstract. An intercomparison of zenith-sky UV-visible spectrometers was held at Camborne, UK, for 2 weeks in September 1994. Eleven instruments participated, from nine different European institutes which were involved with the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME) campaign. Four instruments were of the Systeme d'Analyse d'Observations Z6nithales (SAOZ) type, while the rest were particular to the institutes involved. The results showed that the SAOZ instruments were consistent to within 3% (10 DU) for ozone and 5% for NO 2. For ozone the results from these instruments agreed well with total ozone measurements by Dobson and Brewer spectrophotometers and integrated ozonesondes when the air mass factors for the SAOZ were calculated using the ozonesonde profiles. Differences of up to 10% in ozone and 30% in NO 2 were found between different instruments. In some cases these differences are attributable to the different absorption cross sections used in the analysis of the spectra, but other discrepancies remain to be investigated. A prominent source of error identified in the campaign was uncertainty in the derivation of the amount of absorber in the reference spectrum, which can contribute an error of up to 3% (10

Estimation of Antarctic ozone loss from ground-based total column measurements

“…Ozone is measured in the Chappuis band (450-650 nm) at high SZA between 86 and 91 • every morning and evening. As concluded from various inter-comparison exercises (Roscoe et al, 1999;Vaughan et al, 1997), the measurements from different SAOZ instruments are consistent within ±3%. The main source of uncertainty in the measurements is the air mass factor (AMF) and for instance, the difference in AMF between inside and outside the ozone hole can be up to 10%.…”

Intercomparison of slant column measurements of NO<sub>2</sub> and O<sub>4</sub> by MAX-DOAS and zenith-sky UV and visible spectrometers

“…So far for NO 2 , only stratospheric measurements have been intercompared (Lauder, New Zealand, in 1992 by Hofmann et al, 1995;Camborne, UK, in 1994 by Vaughan et al, 1997;OHP, France, in 1996 by Roscoe et al, 1999;and Andoya, Norway, in 2003 by Vandaele et al, 2005). Here we present results from the first intercomparison of MAX-DOAS as well as zenith-sky ground-based remote sensors of NO 2 .…”

Construction of merged satellite total O<sub>3</sub> and NO<sub>2</sub> time series in the tropics for trend studies and evaluation by comparison to NDACC SAOZ measurements

“…The precision of the NO 2 column is about 11 % and the total accuracy ∼ 21 % . The SAOZ instrument has been qualified by NDACC for ozone and NO 2 measurements during several international intercomparison campaigns (Vaughan et al, 1997;Vandaele et al, 2005). One of the advantages of the SAOZ technique, particularly useful for long series of measurements and comparing those obtained at two independent stations, is the calibration provided by the absorption cross-sections (the same for the full series of data) used in the DOAS analyses and not requiring regular calibrations for correcting possible shifts like for the other ground-based UV spectrophotometers.…”