Global carbon monoxide as retrieved from SCIAMACHY by WFM-DOAS

[摘要] First results concerning the retrieval oftroposphericcarbon monoxide (CO)from satellite solar backscatter radiance measurements in thenear-infrared spectral region (~2.3µm)are presented.The Weighting Function Modified (WFM) DOAS retrieval algorithmhas been used to retrievevertical columns of CO from SCIAMACHY/ENVISAT nadir spectra.We present detailed results for three daysfrom the time periode January to October 2003selected to have good overlap with the daytime CO measurementsof MOPITT onboard EOS Terra.Because the WFM-DOAS Version 0.4 CO columnspresented in this paper are scaledby a constant factor of 0.5 to compensate for an obviousoverestimation we focus on the variability of the retrievedcolumns rather than on their absolute values.It is shown thatplumes 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 theVersion 3 CO columndata product of MOPITT.For example, for measurements over land, where the quality of thedata is typically better than over ocean dueto higher surface reflectivity,the standard deviationof the difference with respect to MOPITT is in the range0.4-0.6x10¹⁸ molecules/cm²and the linear correlationcoefficient is between 0.4 and 0.7.The level of agreement between the data of both sensorsdepends on time and location but is typically within30% for most latitudes.In the southern hemisphere outside AntarcticaSCIAMACHY tends to give systematically higher values than MOPITT.More studies are needed to find out what the reasons for theobserved differences with respect to MOPITT are and how the algorithmcan be modified to improve the quality of the CO columns as retrievedfrom SCIAMACHY.

[学科分类] 大气科学