Regridding of remote soundings: formulation and application to ozone profile comparison

One of the difficulties arising when intercomparing independent measurements of atmospheric constituent profiles consists in homogenizing their respective profile coordinates in order to allow quantitative comparison results. Special care should be devoted in particular to the homogenization of remote sensor measurements, those being indeed intricately bound to their respective numerical grids through discretization rules implied for the evaluation of the retrieval algorithms. Recently, a method of intercomparing remote sounders while allowing for different observational characteristics was proposed by Rodgers and Connor (2003). However, at the time of publication, application of this method was restricted to comparisons of identical state vectors. We propose to relax this condition by the use of linear transformation functions to homogenize the products of independent retrievals. We combine this technique with the Rodgers and Connor procedure to compare independent ozone profile measurements by the Global Ozone Monitoring Experiment (GOME) and a ground-based microwave radiometer (MW). Verification of the achieved results is obtained by considering a second series of MW retrievals, evaluated directly on the GOME numerical grid.