Abstract
Abstract. In September 2014, a Pandora multi-spectral photometer operated by the SAGE-III project was sent to Lauder, New Zealand, to operate side-by-side with the National Institute of Water and Atmospheric Research's (NIWA) Network for Detection of Atmospheric Composition Change (NDACC) certified zenith slant column NO2 instrument to allow intercomparison between the two instruments and for evaluation of the Pandora unit as a potential SAGE-III validation tool for stratospheric NO2. This intercomparison spanned a full year, from September 2014 to September 2015. Both datasets were produced using their respective native algorithms using a common reference spectrum (i.e., 12:00 NZDT (UTC + 13) on 26 February 2015). Throughout the entire deployment period both instruments operated in a zenith-only observation configuration. Though conversion from slant column density (SCD) to vertical-column density is routine (by application of an air mass factor), we limit the current analysis to SCD only. This omission is beneficial in that it provides an intercomparison based on similar modes of operation for the two instruments and the retrieval algorithms as opposed to introducing an air mass factor dependence in the intercomparison as well. It was observed that the current hardware configurations and retrieval algorithms are in good agreement (R > 0.95). The detailed results of this investigation are presented herein.
Highlights
The Stratospheric Aerosol and Gas Experiment (SAGE) missions have provided a legacy of high-quality solar occultation measurements for vertically profiling stratospheric O3 and ultraviolet–visible–near-infrared aerosol extinction coefficients from the upper troposphere into the mesosphere for more than 3 decades (Chu and McCormick, 1979, 1986; Damadeo et al, 2013; Cisewski et al, 2014)
An updated version of the SAGE instrument was integrated into the International Space Station (ISS) in March 2017 with routine observations starting in April
The SAGE-III project will focus on reassessing the state of stratospheric O3 recovery and provide requisite aerosol observations for climate and ozone models
Summary
The Stratospheric Aerosol and Gas Experiment (SAGE) missions have provided a legacy of high-quality solar occultation measurements for vertically profiling stratospheric O3 and ultraviolet–visible–near-infrared aerosol extinction coefficients from the upper troposphere into the mesosphere for more than 3 decades (Chu and McCormick, 1979, 1986; Damadeo et al, 2013; Cisewski et al, 2014) These observations have formed a crucial component for understanding ozone trends and the influence of stratospheric chemistry and aerosol on ozone mixing ratios and climate. An alternative method that provides some corroboration to the SAGE-III measurement quality is a comparison with ground-based differential optical absorption spectroscopy (DOAS; e.g., Platt and Stutz, 2008) or Fourier transform spectroscopy (FTS; e.g., Wang et al, 2010) measurements of the column NO2 using zenith-looking instruments that measure scattered light across the ultraviolet and visible wavelengths These observations can be used to infer, among other species, column NO2 as a function of solar zenith angle (SZA). We report the results of a comparison of observations by a NIWA owned and operated instrument and the SAGE-III Pandora unit when operated side by side between September 2014 and September 2015 at the NIWA facility in Lauder, New Zealand
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