A linearized radiative transfer model for ozone profile retrieval using the analytical forward-adjoint perturbation theory approach

For the retrieval of ozone profiles from space-borne radiance measurements, a new linearized radiative transfer model LIRA is presented. The model ena bles an effective linearization of the reflectance at the top of the atmosp here with respect to both the ozone density in the different layers of the model atmosphere and the Lambertian surface albedo in the UV of the solar s pectrum. The linearization of the model is based on the forward-adjoint per turbation theory, where the forward and adjoint solution of the scalar radi ative transfer equation in its plane-parallel form are achieved by employin g the Gauss-Seidel iteration technique. For clear sky and aerosol-loaded at mospheres the model provides the reflectance as well as its derivatives wit h respect to ozone density with an accuracy of better than 0.02%. The deriv atives with respect to surface reflection can be calculated with an error o f less than 0.05%. The suitability of the model for ozone profile retrieval is demonstrated. Therefore ozone profiles are retrieved from 156 modeled r adiance measurements, simulating real radiance measurements of the Global O zone Monitoring Experiment (GOME) spectrometer in the UV. The comparison of the retrieved profiles using the proposed model LIRA with a reference retr ieval shows small deviations in the stratosphere and upper troposphere of l ess than 1% and tolerable differences in the middle and lower troposphere o f up to 10% in the mean profile at ground level.