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| Titel |
Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS) using non-coincident measurements |
| VerfasserIn |
M. I. Hegglin, C. D. Boone, G. L. Manney, T. G. Shepherd, K. A. Walker, P. F. Bernath, W. H. Daffer, P. Hoor, C. Schiller |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 6 ; Nr. 8, no. 6 (2008-03-13), S.1483-1499 |
| Datensatznummer |
250005919
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| Publikation (Nr.) |
 copernicus.org/acp-8-1483-2008.pdf |
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| Zusammenfassung |
| 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 and ozonesonde 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. Validation
based on coincidences therefore suffers from geophysical noise. Two
alternative methods for the validation of satellite data are introduced,
which avoid the usual need for coincident measurements: tracer-tracer
correlations, and vertical tracer profiles relative to tropopause height.
Both are increasingly being used for model validation as they strongly
suppress geophysical variability and thereby provide an "instantaneous
climatology". This allows comparison of measurements between non-coincident
data sets which yields information about the precision and a statistically
meaningful error-assessment of the ACE-FTS satellite data in the UTLS. By
defining a trade-off factor, we show that the measurement errors can be
reduced by including more measurements obtained over a wider longitude range
into the comparison, despite the increased geophysical variability. Applying
the methods then yields the following upper bounds to the relative
differences in the mean found between the ACE-FTS and SPURT aircraft measurements in the
upper troposphere (UT) and lower stratosphere (LS), respectively: for CO
±9% and ±12%, for H2O ±30% and ±18%, and for O3
±25% and ±19%. The relative differences for O3 can be narrowed
down by using a larger dataset obtained from ozonesondes, yielding a high
bias in the ACE-FTS measurements of 18% in the UT and relative differences
of ±8% for measurements in the LS. When taking into account the smearing
effect of the vertically limited spacing between measurements of the ACE-FTS
instrument, the relative differences decrease by 5–15% around the
tropopause, suggesting a vertical resolution of the ACE-FTS in the UTLS of
around 1 km. The ACE-FTS hence offers unprecedented precision and vertical
resolution for a satellite instrument, which will allow a new global
perspective on UTLS tracer distributions. |
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