Regridding of Remote Sensing Retrievals: Formalism and Application to GOME vs Microwave Ozone Profile Comparison

One of the difficulties commonly arising in geophysical intercomparison studies is the inhomogeneity of the comparison data. As a matter of fact, two independent measurements of an atmospheric constituent profile to be compared to each other will generally be expressed in different units, and onto fully different vertical grids. For many applications, these differences can be most simply eliminated by the application of interpolation or averaging operators, or of auxiliary profiles such as temperature and pressure to achieve homogenized profile units. In the case of profiles retrieved from remote sounding measurements using advanced techniques such as optimal estimation, however, the situaton is complicated by the different dependency on a-priori information, expressed in differing averaging kernels. In order to solve this problem, a formalism was developed that allows the homogenization of retrieval products (and in particular of their numerical grids) without preliminary alteration of the respective retrieval algorithms. In a recent study [1], this formalism was applied to the comparison of independent ozone profile measurements by the Global Ozone Monitoring Experiment (GOME) and a ground-based microwave radiometer (MW) during 2000. We present the results of this study, and describe the employed linear profile transformation method.