Atmos. Chem. Phys. Discuss., 7, 13861-13882, 2007
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements
M. I. Hegglin1, P. F. Bernath2,3, C. D. Boone3, W. H. Daffer4, P. Hoor5, G. L. Manney6,7, C. Schiller8, K. Strong1, and K. A. Walker1,3
1Department of Physics, University of Toronto, Toronto, Canada
2Department of Chemistry, University of York, York, UK
3Department of Chemistry, University of Waterloo, Waterloo, Canada
4Columbus Technologies Inc., Pasadena, California, USA
5Max Planck Institute for Chemistry, Air Chemistry, Mainz, Germany
6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
7New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA
8Institute for Chemistry and Dynamics of the Geosphere, Stratosphere, Research Centre Jülich GmbH, Jülich, Germany

Abstract. CO, O3, and H2O data in the upper troposphere/lower stratosphere (UTLS) measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on Canada's SCISAT-1 satellite are validated using aircraft measurements. In the UTLS, validation of chemical trace gas measurements is a challenging task due to small-scale variability in the tracer fields, strong gradients of the tracers across the tropopause, and scarcity of measurements suitable for validation purposes. Two alternative methods for the validation of the satellite data are introduced, which avoid the usual need for coincident measurements: tracer-tracer correlations, and vertical profiles relative to the tropopause height. Both largely reduce geophysical variability and thereby provide an "instantaneous climatology", allowing measurement comparison with non-coincident data which yields information about the precision, and a statistically meaningful error-assessment of the ACE-FTS satellite data. We found that the ACE-FTS CO and lower stratospheric O3 agree with the aircraft measurements within ±10% and ±5%, respectively. The ACE-FTS O3 in the UT exhibits a high bias of up to 40%. H2O indicates a low bias with relative differences of around 20% in the LS and 40% in the UT, respectively. When taking into account the smearing effect of the vertically limited spacing between measurements of the ACE-FTS instrument, the errors decrease by 5–15% around the tropopause. The ACE-FTS instrument hence offers unprecedented precision and vertical resolution in the UTLS, that will allow a new global perspective on UTLS tracer distributions.

Citation: Hegglin, M. I., Bernath, P. F., Boone, C. D., Daffer, W. H., Hoor, P., Manney, G. L., Schiller, C., Strong, K., and Walker, K. A.: Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements, Atmos. Chem. Phys. Discuss., 7, 13861-13882, doi:10.5194/acpd-7-13861-2007, 2007.
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