Reproducibility of total ozone column monitoring by the Arosa Brewer spectrophotometer triad

The historical review of the total ozone column measurements with the Arosa Brewer triad in operation since 1998 is presented. The calibration history of the different instruments and the data quality control performed at Arosa are described. Over the last 15years, the Brewer triad shows a dispersion of approximate to 0.4% between the three collocated instruments and a long-term stability of 0.5%. These values are a reference metric achievable with well-maintained Brewer instruments under favorable measurement conditions. Plain Language Summary The monitoring of the ozone layer is important to understand the changes of the Earth atmosphere. The instruments used to record these slow changes must have a very good long-term stability. The characteristics of the instruments part of the world's longest ozone column series from Arosa, Switzerland, are analyzed in this publication.