It is based on an optimal estimation scheme which supports both probabilistic

It is based on an optimal estimation scheme which

This preview shows page 27 - 29 out of 42 pages.

data processor of higher sophistication is under development. It is based on an optimal estimation scheme, which supports both probabilistic and non-probabilistic covariance matrices for the regularisation of the retrieval problem. Full retrieval diagnostics in terms of covariance matrices of the retrieval results, averaging kernel matrices, measure of the vertical resolution etc. is also provided. The development work for the water vapour and temperature retrievals focuses - as part of the overall development of this processor - on the optimisation and fine-tuning of the retrieval of non-standard observations for which the routine processing by ESA will most probably not be optimised. During the year 2001 we have concentrated on 27
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the retrieval of water vapour in the tropical UT/LS from the standard (covering 6 to 68 km altitude in 3 or 5 km steps) and the specific STE observation scenario (covering 5 to 40 km in 1.5 km steps below 20 km). For mid-latitude conditions and the standard observation scenario blind test retrievals from synthetic spectra have also been performed. Besides the work on the improvement of retrieval approaches, we have designed the validation approach following the idea of Rodgers and Connor, and provided the necessary validation tools. For the tropical UT/LS region, the retrieval approach for water vapour has been developed by an appropriate selection of spectral micro windows, and by fine-tuning the regularisation of the retrieval via test retrievals using synthetic data. Figure WP5-4 shows the result of a test retrieval based on synthetic data for the tropical UT/LS region and the specific STE observation scenario (covering 5 to 40 km in 1.5 km steps below 20 km). Water vapour and temperature in the altitude range of the measurement were the parameters to be retrieved. The reference spectra had been perturbed by measurement noise according to the MIPAS/ENVISAT specification. All other potentially perturbing parameters (interfering gases etc.) have been assumed to be exactly known. The retrieval result shows that the water vapour mixing ratio profile in the altitude range of the observations can be reconstructed very well; the water vapour volume mixing ratio can be retrieved to an uncertainty of about 10% for the given conditions in the tropopause regions, and the hygropause can very well be resolved. Work is in progress to extend the retrieval study to more realistic cases in order to fine-tune the relevant processing parameters, and to systematically inter-compare several combinations of observation and retrieval scenarios. Figure WP5-5 demonstrates the readiness of our retrieval system for real data, namely the MIPAS-balloon data measured on May 8 th , 1998 at Aire sur l'Adour (Friedl-Vallon et al., 2000; Ridolfi et al., 2000). The retrieved profiles achieved for various sets of regularisation 28 Fig. WP5-4 : Results of a test retrieval based on synthetic data for the water vapour profile in the tropical UTLS region. Left panel: Retrieved profile (solid line), reference profile (dashed line), initial guess (dotted line) and error bars due to measurement noise; right panel: deviation from the reference profile compared to the estimated standard deviation.
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