Retrieval of CFC-11 and CFC-12 from Envisat MIPAS observations by means of rapid radiative transfer calculations

An optimal estimation approach has been applied to retrieve CFC-11 and CFC-12 vertical profiles from Envisat MIPAS measurements. Rapid forward modeling during the retrieval process is based on a broad-band approach and the use of emissivity look-up tables for the computation of radiative transfer, yielding accurate results at very low computational costs. In total 150,000 vertical scans of CFC-11 and CFC-12 have been retrieved. Seasonal means and variances are presented for summer and winter 2003. Error analyses show that the total error of the retrieved volume mixing ratios is in the order of 7-10% in the upper troposphere and lower stratosphere. The influence of a priori on the retrieval results is only marginal.