Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 5 2007 10.5194/acpd-7-13861-2007 http://www.atmos-chem-phys-discuss.net/7/13861/2007/ http://www.atmos-chem-phys-discuss.net/7/13861/2007/acpd-7-13861-2007.html http://www.atmos-chem-phys-discuss.net/7/13861/2007/acpd-7-13861-2007.pdf 13861 13882 2007-09-26 Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements M. I. Hegglin michaela@atmosp.physics.utoronto.ca P. F. Bernath C. D. Boone W. H. Daffer P. Hoor G. L. Manney C. Schiller K. Strong K. A. Walker Department of Physics, University of Toronto, Toronto, Canada Department of Chemistry, University of York, York, UK Department of Chemistry, University of Waterloo, Waterloo, Canada Columbus Technologies Inc., Pasadena, California, USA Max Planck Institute for Chemistry, Air Chemistry, Mainz, Germany Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA Institute for Chemistry and Dynamics of the Geosphere, Stratosphere, Research Centre Jülich GmbH, Jülich, Germany 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%. 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