Simultaneous ground-based observations of O3, HCl, N2O, and CH4 over Toronto, Canada by three Fourier transform spectrometers with different resolutions D. Wunch1, J. R. Taylor1, D. Fu2, P. Bernath2,3, J. R. Drummond1,4, C. Midwinter1, K. Strong1, and K. A. Walker1,2 1Department of Physics, University of Toronto, Toronto, ON, M5S 1A7, Canada 2Department of Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1, Canada 3Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK 4Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 3J5, Canada
Abstract. An intercomparison of three Fourier transform spectrometers (FTSs)
with significantly different resolutions is presented. The
highest-resolution instrument has a maximum optical path difference
of 250 cm, and the two lower-resolution instruments have
maximum optical path differences of 50 cm and 25 cm.
The results indicate that the two lower-resolution instruments can
retrieve total column amounts of O3, HCl, N2O
and CH4 using the SFIT2 retrieval code with percent
differences from the high-resolution instrument generally better
than 4%. Total column amounts of the stratospheric species
(O3 and HCl) have larger differences than those of
the tropospheric species (N2O and CH4). Instrument
line shape (ILS) information is found to be of critical importance
when retrieving total columns of stratospheric gases from the
lower-resolution instruments. Including the ILS information in the
retrievals significantly reduces the difference in total column
amounts between the three instruments. The remaining errors for
stratospheric species total column amounts can be attributed to the
lower sensitivity of the lower-resolution FTSs to the stratosphere.
Citation: Wunch, D., Taylor, J. R., Fu, D., Bernath, P., Drummond, J. R., Midwinter, C., Strong, K., and Walker, K. A.: Simultaneous ground-based observations of O3, HCl, N2O, and CH4 over Toronto, Canada by three Fourier transform spectrometers with different resolutions, Atmos. Chem. Phys., 7, 1275-1292, doi:10.5194/acp-7-1275-2007, 2007.