Global carbon monoxide as retrieved from SCIAMACHY by WFM-DOAS M. Buchwitz, R. de Beek, K. Bramstedt, S. Noël, H. Bovensmann, and J. P. Burrows Institute of Environmental Physics (iup), University of Bremen FB1, Bremen, Germany
Abstract. First results concerning the retrieval of
carbon monoxide (CO)
from satellite solar backscatter radiance measurements in the
near-infrared spectral region (~2.3µm)
The Weighting Function Modified (WFM) DOAS retrieval algorithm
has been used to retrieve
vertical columns of CO from SCIAMACHY/ENVISAT nadir spectra.
We present detailed results for three days
from the time periode January to October 2003
selected to have good overlap with the daytime CO measurements
of MOPITT onboard EOS Terra.
Because the WFM-DOAS Version 0.4 CO columns
presented in this paper are scaled
by a constant factor of 0.5 to compensate for an obvious
overestimation we focus on the variability of the retrieved
columns rather than on their absolute values.
It is shown that
plumes of CO resulting from, e.g. biomass burning in Africa,
are detectable with single overpass SCIAMACHY data.
Globally, the SCIAMACHY CO columns are in reasonable agreement with the
Version 3 CO column
data product of MOPITT.
For example, for measurements over land, where the quality of the
data is typically better than over ocean due
to higher surface reflectivity,
the standard deviation
of the difference with respect to MOPITT is in the range
and the linear correlation
coefficient is between 0.4 and 0.7.
The level of agreement between the data of both sensors
depends on time and location but is typically within
30% for most latitudes.
In the southern hemisphere outside Antarctica
SCIAMACHY tends to give systematically higher values than MOPITT.
More studies are needed to find out what the reasons for the
observed differences with respect to MOPITT are and how the algorithm
can be modified to improve the quality of the CO columns as retrieved
Citation: Buchwitz, M., de Beek, R., Bramstedt, K., Noël, S., Bovensmann, H., and Burrows, J. P.: Global carbon monoxide as retrieved from SCIAMACHY by WFM-DOAS, Atmos. Chem. Phys., 4, 1945-1960, doi:10.5194/acp-4-1945-2004, 2004.