Abstract. This paper presents a validation study of SCanning
Imaging Absorption spectroMeter for Atmospheric
CHartographY (SCIAMACHY) carbon monoxide (CO) total
column measurements from the Iterative Maximum Likelihood
Method (IMLM) algorithm using ground-based spectrometer
observations from twenty surface stations for the
five year time period of 2003–2007.
Overall we find a good agreement between SCIAMACHY
and ground-based observations for both mean values as well
as seasonal variations. For high-latitude Northern Hemisphere stations absolute
differences between SCIAMACHY and ground-based measurements
are close to or fall within the SCIAMACHY CO
2 precision of 0.2×1018 molecules/cm2 (10%) indicating
that SCIAMACHY can observe CO accurately at high
Northern Hemisphere latitudes.
For Northern Hemisphere mid-latitude stations the validation
is complicated due to the vicinity of emission sources
for almost all stations, leading to higher ground-based measurements
compared to SCIAMACHY CO within its typical
sampling area of 8 ×8.
Comparisons with Northern Hemisphere mountain stations
are hampered by elevation effects. After accounting
for these effects, the validation provides satisfactory results