Retrieval error comparison for several inversion techniques used in limb-scanning millimeter wave spectroscopy

PULIAFITO, E.; BEVILACQUA, R.M.; OLIVERO, J.; DEGENHARDT, W.

JOURNAL OF GEOPHYSICAL RESEARCH

American Geophysical Union

Lugar: Washington D.C.; Año: 1995 vol. 100 p. 14257 - 14267

0148-0227

The Rodgers formal retrieval error analysis allows the quantitative determination of such important retrieval properties as the total retrieval error, the contribution from the relevant error sources, the vertical resolution, and the inversion bias. Therefore it is a powerful tool for the objective evaluation and comparison of retrieval techniques. We have applied this error analysis to five numerical inversion techniques (the direct inversion, the linear constrained inversion, the optimal estimation techniques, the general relaxation technique, and the Twomey-modified Chahine relaxation inversion) used for the retrieval of middle atmospheric constituent concentrations from limb-scanning millimeter-wave spectroscopic measurements. As an example of such measurements, we use the geometry and instrument characteristic of the millimeter-wave atmospheric sounder (MAS) experiment, which has flown on the first three ATLAS) series of spacelab shuttle missions mission (March 1992, April 1993 and November 1994). We find that the relaxation methods have somewhat better vertical resolution but are slighty more sensitive to measurements errors than the constrained matrix methods. However, for the assumed MAS instruments characteristics, the total retrieved error is similar for all of the inversion schemes. We also tested the error predicted by the theoretical analysis against numerical simulations and find good agreement. Trade-offs of these retrieval characteristics for several cases of measurements error and a-priori profile uncertainty are presented.