Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements

M. I. Hegglin (1) , P. F. Bernath (2, 3) , C. D. Boone (3) , W. H. Daffer (4) , P. Hoor (5) , G. L. Manney (6, 7) , C. Schiller (8) , K. Strong (1) , K. A. Walker (1, 3)

1 Department of Physics [Toronto]
2 Department of Chemistry
3 Department of Chemistry
4 Columbus Technologies Inc.
5 MPIC - Max Planck Institute for Chemistry
6 JPL - Jet Propulsion Laboratory
7 NMT - New Mexico Institute of Mining and Technology [New Mexico Tech]
8 Institute for Chemistry and Dynamics of the Geosphere

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.

Domaines: Océan, Atmosphère

M. I. Hegglin, P. F. Bernath, C. D. Boone, W. H. Daffer, P. Hoor, et al.. Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements. Atmospheric Chemistry and Physics Discussions, 2007, 7 (5), pp.13861-13882. ⟨hal-00303109⟩