Preprints
https://doi.org/10.5194/amt-2020-324
https://doi.org/10.5194/amt-2020-324

  10 Sep 2020

10 Sep 2020

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

The world Brewer reference triad – updated performance assessment and new double triad

Xiaoyi Zhao1, Vitali Fioletov1, Michael Brohart1, Volodya Savastiouk2, Ihab Abboud1, Akira Ogyu1, Jonathan Davies1, Reno Sit1, Sum Chi Lee1, Alexander Cede3,4, Martin Tiefengraber4,5, Moritz Müller4,5, Debora Griffin1, and Chris McLinden1 Xiaoyi Zhao et al.
  • 1Air Quality Research Division, Environment and Climate Change Canada, Toronto, M3H 5T4, Canada
  • 2International Ozone Services Inc., Toronto, Canada
  • 3NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 4LuftBlick, Innsbruck, Austria
  • 5Department of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria

Abstract. The Brewer ozone spectrophotometer (the Brewer) was designed at Environment and Climate Change Canada (ECCC) in the 1970s to make accurate automated total ozone column measurements. Since the 1980s, the Brewer has become a World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) standard ozone monitoring instrument. Now, more than 230 Brewers have been produced. To assure the quality of the Brewer measurements, a calibration chain is maintained, i.e., first, the reference instruments are independently absolutely calibrated, and then the calibration is transferred from the reference instrument to the travelling standard, and subsequently from the travelling standard to field instruments. ECCC has maintained the world Brewer reference instruments since the 1980s to provide transferable calibration to field instruments at monitoring sites. Three single-monochromator (Mark II) type instruments (serial numbers #008, #014, and #015) formed this world Brewer reference triad (BrT), and started their service in Toronto, Canada in 1984. In the 1990s, the Mark III type Brewer (known as the double Brewer) was developed, which has two monochromators to reduce the internal instrumental stray light. The double Brewer world reference triad (BrT-D) was formed in 2013 (serial numbers #145, #187 and #191), co-located with the BrT. The first assessment of the BrT's performance was made in 2005, covering the period between 1984 and 2004 (Fioletov et al., 2005). The current work provides an updated assessment of the BrT's performance (from 1999 to 2019) and the first comprehensive assessment of the BrT-D. The random uncertainties of individual reference instruments are within the WMO/GAW requirement of 1 % (0.49 % and 0.42 % for BrT and BrT-D, respectively). The long-term stability of the reference instruments is also evaluated in terms of uncertainties of the key instrument characteristics: the extraterrestrial calibration constant (ETC) and effective ozone absorption coefficients (both having an effect of less than 2 % on total column ozone). Measurements from a ground-based instrument (Pandora spectrometer) and satellites (eleven datasets, including the most recent high-resolution satellite, TROPOspheric Monitoring Instrument), and reanalysis model (the second Modern-Era Retrospective analysis for Research and Applications, MERRA-2) are used to further assess the performance of world Brewer reference instruments and to provide a context for the requirements of stratospheric ozone observations during the last two decades.

Xiaoyi Zhao et al.

 
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Xiaoyi Zhao et al.

Xiaoyi Zhao et al.

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Short summary
The Brewer spectrophotometer is one of the main instruments for measurements of atmospheric total column ozone. The global Brewer network largely relies on the world reference instruments (the Brewer triad) operated by Environment and Climate Change Canada since the early 1980s. This study provides an updated assessment (1999–2019) of the reference instrument performance, in terms of random uncertainties and long-term stability.