Comparison of the total ozone measurements taken by the Brewer and Dobson spectrophotometr at Belsk in 2002

Total ozone measurements taken by means of the Dobson No. 84 and the Brewer No. 64 instruments at Belsk, Poland, in 2002, have been compared. The quasi-simultaneously (to 0.5 hour time difference) measured DS total ozone data (1760 Dobson-Brewer pairs) were analysed to establish main characteristics of the differences. Seasonal variation of the Dobson-Brewer differences and the stratospheric temperature influence on the difference as well as their mu dependence were examined. A multiple regression model of the differences testing several explaining variables (model regressors) was used. Among the studied regressors were the following: aerosol optical depth at 320 nm, temperature inside the Brewer instrument, mu multiplied by total ozone, temperature, geopotential, and potential vorticity at several levels in the troposphere and the stratosphere. Only three regressors were statistically significant, namely the temperature at 50 hPa level, temperature at the tropopause level, and total ozone multiplied by mu. Cases of the extreme Dobson-Brewer differences reaching 7-8% were analysed and the role the atmospherical aerosol depth at 320 nm was assessed.