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| Titel |
Tropospheric CO vertical profiles deduced from total columns using data assimilation: methodology and validation |
| VerfasserIn |
L. El Amraoui, J.-L. Attié, P. Ricaud, W. A. Lahoz, A. Piacentini, V.-H. Peuch, J. X. Warner, R. Abida, J. Barré, R. Zbinden |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 9 ; Nr. 7, no. 9 (2014-09-18), S.3035-3057 |
| Datensatznummer |
250115904
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| Publikation (Nr.) |
 copernicus.org/amt-7-3035-2014.pdf |
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| Zusammenfassung |
This paper presents a validation of a method to derive the vertical
profile of carbon monoxide (CO) from its total column using
data assimilation.
We choose version 3 of MOPITT CO total columns to validate
the proposed method. MOPITT products have the advantage of providing both the
vertical profiles and the total columns of CO. Furthermore,
this version has been extensively validated by comparison with many
independent data sets, and has been used in many scientific
studies.
The first step of the paper consists in the specification of
the observation errors based on the chi-square (χ2) test. The
observations have been binned according to three types: over land during
daytime, over land during night-time, and over sea. Their respective
errors using the χ2 metric have been found to be 8, 11 and 7%.
In the second step, the CO total columns, with their specified errors, are used
within the assimilation system to estimate the vertical profiles. These are
compared to the retrieved profiles of MOPITT V3 at global and regional
scales. Generally, the two data sets show similar patterns and good agreement
at both scales. Nevertheless, total column analyses slightly overestimate CO
concentrations compared to MOPITT observations. The mean bias between both
data sets is +15 and +12% at 700 and 250 hPa, respectively.
In the third step, the assimilation of total column has been compared to the
assimilation of MOPITT vertical profiles. The differences between both
analyses are very small. In terms longitude–latitude maps, the mean bias between the
two data sets is +6 and +8% at the pressure levels 700 and
200 hPa, respectively. In terms of zonal means, the CO
distribution is similar for both analyses, with a mean bias which does not
exceed 12%.
Finally, the two analyses have been validated using
independent observations from the aircraft-based
MOZAIC program
in terms of vertical profiles over eight airports. Over
most airports, both analyses agree well with aircraft profiles. For more than
50% of recorded measurements, the difference between the analyses and
MOZAIC does not exceed 5 ppbv (parts per billion by volume). |
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