This report summarises the quality control, quality assurance and measurements of total ozone at Norrköping and Vindeln during the period 1994-1996. To ensure the quality and link the observations closely to the other ozone data participation in intercomparisons and intemational campaigns are noted. The Dobson #30 instrument was at Arosa in 1995 and showed good agreement with the reference Dobson instrument. The Brewer #006 was compared to the travelling reference Brewer #017 in 1996. Major changes in the measurements and instruments are discussed. In particular the introduction of the new instrument Brewer #128, which was compared to Brewer #017 twice in 1996. The first intercomparison pointed on the need of a change of the calibration whilst the second one was in agreement with the previous one. The new instrument seem to be more sensitive to the environment than the old one is. During the campaign at lzaifa it was noted that the photomultiplier of this instrument went saturated measuring in the UV- A. Fortunately, this will not affect the measurements of the total ozone.
During these three years the ozone-layer has shown many periods of considerable depletion. Now the effects from the Pinatubo eruption has ceased and the sometimes thin layer of ozone can not be attributed to the eventual effects of the volcanic eruption. The extreme deficits of ozone in 1996 and also the down-ward trend, about -8% per decade, in the long-term data presentation are easily seen in the graphs. There will soon be 10 years of almost uninterrupted data available at Norrköping. During winter and spring the observations are delivered almost daily to a European centre in Thessaloniki, Greece, where data are collected. Daily maps are produced showing the total ozone for the northern hemisphere.
The introduction of a Web-site for total ozone (under http://www.smhi.se) has made measurements almost real-time available for a lot of people. It can be viewed as graphs or transferred by ftp. There is also some pages with information as well as some links to related sites. In particular, this is useful for public, media and decision-makers.