A Decade of Stratospheric Water Vapor Profiles from SCIAMACHY Occultation Measurements
Bramstedt, Klaus; NoŽl, Stefan; Azam, Faiza; Alexei, Rozanov; Bovensmann, Heinrich; Burrows, John P.
IUP, University of Bremen, GERMANY

The spectrometer SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on-board ENVISAT measured solar irradiances and Earthshine radiances from the UV to the NIR spectral region in nadir, limb and lunar/solar occultation geometry. Solar occultation measurements are performed during sunrise at northern latitudes (49N to 69N, depending on season). Lunar occultation measurements are limited to the Southern hemisphere and performed, when the waxing moon is in the field of view at local nighttime.

Three datasets of stratospheric water vapor profiles are presented here. Two methods are applied to solar occultation measurements. First method is called "Onion Peeling DOAS" (ONPD) which combines an onion peeling approach with a weighting function DOAS (Differential Optical Absorption Spectroscopy) fit. Second method is an optimal estimation approach with Tikhonov regularization. The latter method is also applied to the lunar occultation measurements.

We will intercompare the two dataset from solar occultation and validate all three datasets with independent measurements. The evolution of the stratospheric water vapor content in the decade covered by the measurements (August 2002 to April 2012) will be investigated, with special care to interhemispheric differences.