The impact of SCIAMACHY near-infrared instrument calibration on CH4 and CO total columns A. M. S. Gloudemans1, H. Schrijver1, Q. Kleipool1,*, M. M. P. van den Broek1, A. G. Straume1,**, G. Lichtenberg1, R. M. van Hees1, I. Aben1, and J. F. Meirink2 1SRON National Institute for Space Research, Utrecht, The Netherlands 2Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands *now at: Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands **now at: the European Space Agency, European Space Research & Technology Centre (ESA-ESTEC), Noordwijk, The Netherlands
Abstract. The near-infrared spectra measured with the SCIAMACHY instrument on
board the ENVISAT satellite suffer from several instrument calibration
The effects of three important instrument calibration
issues on the retrieved methane (CH4) and carbon monoxide (CO)
total columns have been investigated:
the effects of the growing ice layer on the near-infrared detectors, the
effects of the orbital variation of the instrument dark signal, and
the effects of the dead/bad detector pixels. Corrections for each of these
instrument calibration issues have been defined. The retrieved CH4 and CO
total columns including these corrections show good agreement with CO
measurements from the MOPITT satellite instrument and with CH4 model
calculations by the chemistry transport model TM3.
Using a systematic approach, it is shown that all three
instrument calibration issues have a significant effect on the retrieved
CH4 and CO total columns. However, the impact on the CH4 total columns
is more pronounced than for CO, because of its smaller
Results for three different
wavelength ranges are compared and show good agreement.
The growing ice layer and the orbital variation of the
dark signal show a systematic, but time-dependent effect on the retrieved
CH4 and CO total columns, whereas the
effect of the dead/bad pixels
is rather unpredictable: some dead pixels
show a random effect, some more systematic, and others no effect at
all. The importance of accurate corrections for each of
these instrument calibration issues is illustrated using examples
where inaccurate corrections lead to a wrong interpretation
of the results.
Citation: Gloudemans, A. M. S., Schrijver, H., Kleipool, Q., van den Broek, M. M. P., Straume, A. G., Lichtenberg, G., van Hees, R. M., Aben, I., and Meirink, J. F.: The impact of SCIAMACHY near-infrared instrument calibration on CH4 and CO total columns, Atmos. Chem. Phys., 5, 2369-2383, doi:10.5194/acp-5-2369-2005, 2005.