First retrieval of global water vapour column amounts from SCIAMACHY measurements S. Noël, M. Buchwitz, and J. P. Burrows Institute of Environmental Physics/Remote Sensing, University of Bremen, Germany
Abstract. Global water vapour column amounts have been derived for the first time from
measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the European environmental
satellite ENVISAT. For this purpose, two different existing retrieval algorithms have been
adapted, namely the Air Mass Corrected Differential Absorption Spectroscopy
(AMC-DOAS) which was originally designed for GOME and the Weighting Function
Modified Differential Absorption Spectroscopy (WFM-DOAS) which was mainly designed for the retrieval of
CH4, CO2 and CO from SCIAMACHY near-infrared spectra.
Here, both methods have been applied to SCIAMACHY's nadir measurements in the
near-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 water
vapour. In fact, the mean deviation between the SCIAMACHY and the correlative
data sets is much smaller: the SCIAMACHY total water vapour columns are typically about
0.15 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 of
SCIAMACHY to derive water vapour concentrations on the global scale.
Citation: Noël, S., Buchwitz, M., and Burrows, J. P.: First retrieval of global water vapour column amounts from SCIAMACHY measurements, Atmos. Chem. Phys., 4, 111-125, doi:10.5194/acp-4-111-2004, 2004.