First retrieval of global water vapour column amounts from SCIAMACHY measurements

[摘要] Global water vapour column amounts have been derived for the first time frommeasurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the European environmentalsatellite ENVISAT. For this purpose, two different existing retrieval algorithms have beenadapted, namely the Air Mass Corrected Differential Absorption Spectroscopy(AMC-DOAS) which was originally designed for GOME and the Weighting FunctionModified Differential Absorption Spectroscopy (WFM-DOAS) which was mainly designed for the retrieval ofCH₄, CO₂ and CO from SCIAMACHY near-infrared spectra.Here, both methods have been applied to SCIAMACHY's nadir measurements in thenear-visible spectral region around 700 nm.

Taking into account a systematic offset of 10%, the results of these two methods agree within a scatter of about±0.5 g/cm² with corresponding SSM/I and ECMWF water vapour data.This deviation includes contributions from the temporal and spatial variability of watervapour. In fact, the mean deviation between the SCIAMACHY and the correlativedata sets is much smaller: the SCIAMACHY total water vapour columns are typically about0.15 g/cm² lower than the SSM/I values and less than 0.1 g/cm² lower than corresponding ECMWF data.The SCIAMACHY water vapour results agree well with correlative data not only over ocean but also over land, thus showing the capability ofSCIAMACHY to derive water vapour concentrations on the global scale.

[学科分类] 大气科学