Two years of SCIAMACHY measurements: intercomparison of methane total columns from the 1.65 and 2.3-micrometer windows
Hans Schrijver(1), Annemieke Gloudemans(1), Sander Houweling(2) and Ilse Aben(1)
(1) SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands
(2) SRON Netherlands Institute for Space Research, Sorbonnelaan 21, 3584 CA Utrecht, Netherlands
Total columns of methane can be retrieved from two wavelength windows covered by SCIAMACHY: one at 1.65 micron in channel 6, the other around 2.3 micron in channel 8. Depending on the window, specific complications are involved in the interpretation of the results.
In channel 6 the retrieved columns are considerably affected by spatial
variations in optical path length and must therefore be corrected, for example using carbon dioxide columns obtained from the nearby 1.58-micron window. Errors may be introduced in cases where the surface albedo varies rapidly with the wavelength, so that the optical path length becomes wavelength dependent.
In channel 8 these variations are much smaller, although not entirely absent. But in this case there is the need to correct for the effects (absorption and scattering) of the varying ice layer on the detector window, leaving some uncertainty about the adequacy of the correction.
Retrievals from two years of SCIAMACHY measurements in both windows have been performed using SRON instrument calibrations and temperature and moisture profiles from ECMWF data; these results will be presented and compared, and the respective merits of both windows analyzed, also with consideration to model results.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,