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| Titel |
Intercomparison methods for satellite measurements of atmospheric composition: application to tropospheric ozone from TES and OMI |
| VerfasserIn |
L. Zhang, D. J. Jacob, X. Liu, J. A. Logan, K. Chance, A. Eldering, B. R. Bojkov |
| 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 ; 10, no. 10 ; Nr. 10, no. 10 (2010-05-26), S.4725-4739 |
| Datensatznummer |
250008473
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| Publikation (Nr.) |
 copernicus.org/acp-10-4725-2010.pdf |
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| Zusammenfassung |
| We analyze the theoretical basis of three different methods to validate and
intercompare satellite measurements of atmospheric composition, and apply
them to tropospheric ozone retrievals from the Tropospheric Emission
Spectrometer (TES) and the Ozone Monitoring Instrument (OMI). The first
method (in situ method) uses in situ vertical profiles for absolute
instrument validation; it is limited by the sparseness of in situ data. The
second method (CTM method) uses a chemical transport model (CTM) as an
intercomparison platform; it provides a globally complete intercomparison
with relatively small noise from model error. The third method (averaging
kernel smoothing method) involves smoothing the retrieved profile from one
instrument with the averaging kernel matrix of the other; it also provides a
global intercomparison but dampens the actual difference between instruments
and adds noise from the a priori. We apply the three methods to a full year (2006)
of TES and OMI data. Comparison with in situ data from ozonesondes shows
mean positive biases of 5.3 parts per billion volume (ppbv) (10%) for TES
and 2.8 ppbv (5%) for OMI at 500 hPa. We show that the CTM method (using
the GEOS-Chem CTM) closely approximates results from the in situ method
while providing global coverage. It reveals that differences between TES and
OMI are generally less than 10 ppbv (18%), except at northern
mid-latitudes in summer and over tropical continents. The CTM method further
allows for CTM evaluation using both satellite observations. We thus find
that GEOS-Chem underestimates tropospheric ozone in the tropics due to
possible underestimates of biomass burning, soil, and lightning emissions.
It overestimates ozone in the northern subtropics and southern
mid-latitudes, likely because of excessive stratospheric influx of ozone. |
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