Simultaneous measurements of low latitude NO2 and O3 from zenith sky observations in visible region

Preliminary observations and procedure for calculating the total column density of NO2 and O3 from observations of zenith sky spectra with visible spectrometer at 4A resolution are presented in this paper. The optical paths traversed by solar radiation at different solar zenith angles are considered for calculating slant column densities. The process of molecular (Rayleigh) scattering and absorption by NO2 and O3 are considered for calculating the amount of scattered intensity reaching at ground. The results of calculations used for deriving vertical column density of O3 and NO2 are compared with the observations made with Dobson Spectrophotometer. The observed total column density of O3 by this method is found to be about 10 percent less than that obtained by the Dobson Spectrophotometer and that of NO2 is found to be 0.6-1.3 x 10 exp 16 molecules/sq cm over Pune.