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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
13 Jul 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Measurement Techniques (AMT) and is expected to appear here in due course.
A more representative “best representative value” for daily total column ozone reporting
Andrew R. D. Smedley, John S. Rimmer, and Ann R. Webb Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, United Kingdom
Abstract. Long-term trends of total column ozone, assessments of stratospheric ozone recovery and satellite validation are underpinned by a reliance on daily “best representative values” from Brewer spectrophotometers and other ground-based ozone instruments. In turn reporting of these daily total column ozone values to the World Ozone and Ultraviolet Data Centre has traditionally been predicated upon a binomial choice between direct sun and zenith sky observations. For mid- and high-latitude monitoring sites impacted by cloud cover we discuss the potential deficiencies of this approach in terms of its rejection of otherwise valid observations and capability to evenly sample throughout the day. A new methodology is proposed that makes full use of all valid direct sun and zenith sky observations, accounting for unevenly spaced observations and their relative uncertainty, to calculate an improved estimate of the daily mean total column ozone. It is demonstrated that this method can increase the number of contributing observations by a factor of 2.5, increases the sampled time span, and reduces the spread of the representative time by half. No effect on longer-term trends is detected, though for the sample data analysed we observe a mean increase of 2.8 DU (0.82 %) w.r.t. the traditional direct sun vs zenith sky average choice. To complement the new calculation of a best representative value of total column ozone and separate its uncertainty from the spread of observations, we also propose reporting its standard error rather than the standard deviation, together with measures of the full range of values observed.

Citation: Smedley, A. R. D., Rimmer, J. S., and Webb, A. R.: A more representative “best representative value” for daily total column ozone reporting, Atmos. Meas. Tech. Discuss.,, in review, 2017.
Andrew R. D. Smedley et al.

Data sets

UK ozone and UV monitoring site no. 352
A. R. D. Smedley, J. S. Rimmer, and A. R. Webb
Andrew R. D. Smedley et al.


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