Influence of sulfur dioxide trends on Dobson measurements and electrochemical ozone surroundings

Total ozone measurements have been performed at Uccle (50 degree(s)48'N, 4 degree(s)21'E) with Dobson spectrophotometer 40 since August 1971 and with Brewer instrument 16 since July 1983. The reduced thickness of sulfur dioxide (SO2) as calculated from measurements with the Brewer spectrophotometer shows a decreasing trend that is in good agreement with the trend of in situ measurements of SO2 density near the ground in the urban area of Brussels. From the mean annual variation of the ratio of both variables the corresponding correction for SO2 interference of the Dobson instrument data was calculated on a month-by-month basis. From a comparison of the total ozone trends before and after SO2 correction, it appeared that over the whole time period (August 1971 to May 1993) the SO2 decrease at Uccle has induced a fictitious Dobson total ozone trend that amounts to a mean value of -1.47% per decade. More than half of the stations which have been used in the past in ozone trend studies are located within an urban area with a population of over 100,000 and are in consequence possibly affected by air pollution.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.