Data Fusion of IASI and GOME-2 measurements

Remote sensing observations of the composition of Earth's atmosphere are performed with instruments operating on space-borne and airborne platforms, as well as from ground-based stations. In this context, vertical profiles of atmospheric variables are often obtained with an inversion procedure (retrieval) from the observed radiances. When one or more instruments observe the same portion of atmosphere, the information obtained from the different measurements can be combined in order to obtain a unique vertical profile of improved quality with respect to that of the profiles retrieved from the single observations. The most comprehensive way to combine different measurements of the same quantity is considered to be the simultaneous retrieval, in which all the observations are used together as inputs of the retrieval that produces the common profile. However, recently a new method, referred to as Complete Data Fusion 1 , was proposed that, in linear approximation conditions, provides products equivalent to that of the simultaneous retrieval with simpler implementation requirements. Here, we present the first results of the application of the Complete Data Fusion method to measurements of ozone vertical profiles performed by IASI and GOME-2. The inputs of the method are the profiles retrieved from IASI and from GOME-2 measurements characterized by their a priori information, covariance matrices and averaging kernel matrices. The output consists of a single profile also characterized by an a priori information, a covariance matrix and an averaging kernel matrix, which collect all the information content present in the input profiles. The quality of the fused profile is compared with the quality of the original profiles retrieved from IASI and GOME-2 measurements, in terms of errors and number of degrees of freedom. The discussion also faces the strategies adopted to allow the fusion of non-coincident measurements that are characterized by different systematic errors and the implications of these choices in terms of information content of the fused product. Possible follow-ons of this research can be the validation of the results of Complete Data Fusion against collocated ozone-soundings and the comparison of the fused products with the ozone profiles retrieved by simultaneous inversion of IASI and GOME-2 measurements, in order to verify the equivalence between the two approaches.