Estimation of the error covariance matrix for IASI radiances and its impact on the assimilation of ozone in a chemistry transport model

Abstract. In atmospheric chemistry retrievals and data assimilation systems, observation errors associated with satellite radiances are chosen empirically generally treated as uncorrelated. this work, we estimate inter-channel error covariances for the Infrared Atmospheric Sounding Interferometer (IASI) evaluate their impact on ozone transport model MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle). The method used to calculate is a diagnostic based analysis residual statistics already adopted in many numerical weather prediction centres. We subset of 280 channels covering spectral range between 980 1100 cm−1 observation-error covariance matrix. This includes ozone-sensitive window channels. computed hourly 3D-Var analyses compared resulting O3 fields against ozonesondes measurements provided by Microwave Limb Sounder (MLS) Ozone Monitoring Instrument (OMI). results show significant differences using estimated matrix respect empirical diagonal employed previous studies. validation independent reports improvement, especially tropical stratosphere. computational cost has also been reduced when system, reducing number iterations needed minimizer converge.