A summary of the quality control, quality assurance and measurements of total ozone at Norrköping and Vindeln during the period 1997-1999 is made. The Brewer #006 and Brewer #128 were compared to the travelling reference Brewer #017 at Vindeln in 1999. Major changes in the measurements and instruments are discussed. The reprocessing of all Brewer data since 1996 and the introduction of the new format recommended by WOUDC at the end of 1999 are documented.
At the end of this three-year period the ozone layer has shown an increase after many years with several periods of considerable depletion. Therefore, the previous downward trend that was as large as -8% per decade has disappeared. The data set consists of 12 years of almost uninterrupted data at Norrköping. Most of the gaps have been possible to fill with satellite data to have monthly values based on a complete set of daily values. An intercomparison between ground based and TOMS Version 7 satellite based data shows an astonishing agreement in most cases.
Data recorded at Abisko in 1926 and 1927 on the initiative of G.M.B. Dobson was found in the archive. They were recomputed to modem scales and the result shows that the thickness of the ozone layer at that time is similar to the present thickness. The long-term data sets now available from Vindeln and Norrköping give the opportunity to study the temporal and in some respect also the spatial characteristics of the total ozone. Both the spatial correlation and he auto-correlation vary considerably over time.
The Web-site for total ozone (under http://www.smhi.se) has made measurements available fora lot of people in almost real-time. Ozone data can be viewed as graphs or transferred by ftp. There are also some pages with general information as well as some links to related sites. In particular, this method for distribution of information has been found to be useful for the public, media and decision-makers.