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| Titel |
The detection of post-monsoon tropospheric ozone variability over south Asia using IASI data |
| VerfasserIn |
B. Barret, E. Flochmoën, B. Sauvage, E. Pavelin, M. Matricardi, J. P. Cammas |
| 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 ; 11, no. 18 ; Nr. 11, no. 18 (2011-09-16), S.9533-9548 |
| Datensatznummer |
250010078
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| Publikation (Nr.) |
 copernicus.org/acp-11-9533-2011.pdf |
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| Zusammenfassung |
| The ozone (O3) variability over south Asia during the 2008 post-monsoon
season has been assessed using measurements from the MetOP-A/IASI instrument
and O3 profiles retrieved with the SOftware for a Fast Retrieval of IASI
Data (SOFRID). The information content study and error analyses carried out
in this paper show that IASI Level 1 data can be used to retrieve
tropospheric O3 columns (TOC, surface-225 hPa) and UTLS columns
(225–70 hPa) with errors smaller than 20%. Validation with global
radiosonde O3 profiles obtained during a period of 6 months show the
excellent agreement between IASI and radiosonde for the UTLS with correlation
coefficient R > 0.91 and good agreement in the troposphere with correlation
coefficient R > 0.74. For both the UTLS and the troposphere Relative Standard
Deviations (RSD) are lower than 23%. Comparison with in-situ
measurements from the MOZAIC program around Hyderabad demonstrates that IASI
is able to capture the TOC inter and intra-seasonal variability in central
India. Nevertheless, the agreement is mitigated by the fact that the
smoothing of the true O3 profiles by the retrieval results in a reduction
of the TOC variability detected by IASI relative to the variability observed
by in situ instruments. The post-monsoon temporal variability of the vertical
profile of O3 around Hyderabad has been investigated with MOZAIC
observations. These observations from airborne instruments show that
tropospheric O3 is steadily elevated during most of the studied period
with the exception of two sharp drops following the crossing of tropical
storms over India. Lagrangian simulations with the FLEXPART model indicate
that elevated O3 concentrations in the middle troposphere near Hyderabad
are associated with the transport of UTLS air-masses that have followed the
Subtropical Westerly Jet (SWJ) and subsided over northern India together with
boundary layer polluted air-masses transported from the Indo-gangetic plain
by the north-easterly trades. Low O3 concentrations result from the uplift
and westward transport of pristine air-masses from the marine boundary layer
of the Bay of Bengal by tropical storms. In order to extend the analysis of
tropospheric O3 variability to the whole of south Asia, we have used
IASI-SOFRID O3 data. We show that IASI O3 data around Hyderabad were
able to capture the fast variability revealed by MOZAIC. Furthermore, their
spatio-temporal coverage demonstrates that the behaviour of tropospheric
O3 observed near Hyderabad extended over most of central and south India
and part of the Bay of Bengal. This result highlights the ability of the IASI
sensor to capture fast changes in chemical composition related to dramatic
tropical weather conditions. |
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