Depolarization ratio of the zenith scattered radiation and measured NO2 slant columns

The present paper deals with the factors influencing the accuracy of the DOAS and in particularly, with the changing of the depolarization ratio of the zenith scattered radiation and related variations of the retrieved NO:! slant column. Ground based measurements caried out during 1997 and 1998 of the polarisation state of the zenith-scattered radiation and the NO2 slant columns have been obtained in 4075 Angstrom - 4640 Angstrom spectral interval. The depolarization ratio is calculated from the spectra registered with a sheet linear polarizer, inserted into the instrument. A linear regression analysis is applied to retrieve NO2 slant columns. The obtained results are analysed and discussed.