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Volume 9, issue 12
Atmos. Meas. Tech., 9, 5747–5761, 2016
https://doi.org/10.5194/amt-9-5747-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Twenty-five years of operations of the Network for the Detection...

Atmos. Meas. Tech., 9, 5747–5761, 2016
https://doi.org/10.5194/amt-9-5747-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Nov 2016

Research article | 30 Nov 2016

Accuracy, precision, and temperature dependence of Pandora total ozone measurements estimated from a comparison with the Brewer triad in Toronto

Xiaoyi Zhao1, Vitali Fioletov2, Alexander Cede3,4, Jonathan Davies2, and Kimberly Strong1 Xiaoyi Zhao et al.
  • 1Department of Physics, University of Toronto, Toronto, M5S 1A7, Canada
  • 2Environment and Climate Change Canada, Toronto, M3H 5T4, Canada
  • 3NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 4LuftBlick, Kreith, Austria

Abstract. This study evaluates the performance of the recently developed Pandora spectrometer by comparing it with the Brewer reference triad. This triad was established by Environment and Climate Change Canada (ECCC) in the 1980s and is used to calibrate Brewer instruments around the world, ensuring high-quality total column ozone (TCO) measurements. To reduce stray light, the double Brewer instrument was introduced in 1992, and a new reference triad of double Brewers is also operational at Toronto. Since 2013, ECCC has deployed two Pandora spectrometers co-located with the old and new Brewer triads, making it possible to study the performance of three generations of ozone-monitoring instruments. The statistical analysis of TCO records from these instruments indicates that the random uncertainty for the Brewer is below 0.6 %, while that for the Pandora is below 0.4 %. However, there is a 1 % seasonal difference and a 3 % bias between the standard Pandora and Brewer TCO data, which is related to the temperature dependence and difference in ozone cross sections. A statistical model was developed to remove this seasonal difference and bias. It was based on daily temperature profiles from the European Centre for Medium-Range Weather Forecasts ERA-Interim data over Toronto and TCO from the Brewer reference triads. When the statistical model was used to correct Pandora data, the seasonal difference was reduced to 0.25 % and the bias was reduced to 0.04 %. Pandora instruments were also found to have low air mass dependence up to 81.6° solar zenith angle, comparable to double Brewer instruments.

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This study evaluates the performance of the recently developed Pandora spectrometer by comparing it with the Brewer reference triad. The instrument random uncertainty, total column ozone temperature dependence, and ozone air mass dependence have been determined using two Pandora and six Brewer instruments. In general, Pandora and Brewer instruments both have very low random uncertainty and air mass dependence. However, the Brewer has smaller ozone temperature dependence than Pandora.
This study evaluates the performance of the recently developed Pandora spectrometer by comparing...
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