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| Titel |
Springtime daily variations in lower-tropospheric ozone over east Asia: the role of cyclonic activity and pollution as observed from space with IASI |
| VerfasserIn |
G. Dufour, M. Eremenko, J. Cuesta, C. Doche, G. Foret, M. Beekmann, A. Cheiney, Y. Wang, Z. Cai, Y. Liu, M. Takigawa, Y. Kanaya, J.-M. Flaud |
| 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 ; 15, no. 18 ; Nr. 15, no. 18 (2015-09-29), S.10839-10856 |
| Datensatznummer |
250120064
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| Publikation (Nr.) |
 copernicus.org/acp-15-10839-2015.pdf |
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| Zusammenfassung |
| We use satellite observations from IASI (Infrared Atmospheric Sounding
Interferometer) on board the MetOp-A satellite to evaluate the springtime
daily variations in lower-tropospheric ozone over east Asia. The
availability of semi-independent columns of ozone from the surface up to 12
km simultaneously with CO columns provides a powerful observational data set
to diagnose the processes controlling tropospheric ozone enhancement on
synoptic scales. By combining IASI observations with meteorological
reanalyses from ERA-Interim, we develop an analysis method based only on IASI
ozone and CO observations to identify the respective roles of the
stratospheric source and the photochemical source in ozone distribution and
variations over east Asia. The succession of low- and high-pressure
systems drives the day-to-day variations in lower-tropospheric ozone. A case
study analysis of one frontal system and one cut-off low system in May 2008
shows that reversible subsiding and ascending ozone transfers in the
upper-troposphere–lower-stratosphere (UTLS) region, due to the tropopause perturbations
occurring in the vicinity of low-pressure systems, impact free and
lower-tropospheric ozone over large regions, especially north of
40° N, and largely explain the ozone enhancement observed with IASI
for these latitudes. Irreversible stratosphere–troposphere exchanges of
ozone-rich air masses occur more locally in the southern and southeastern
flanks of the trough. The contribution to the lower-tropospheric ozone column
is difficult to dissociate from the tropopause perturbations generated by
weather systems. For regions south of 40° N, a significant
correlation has been found between lower-tropospheric ozone and carbon
monoxide (CO) observations from IASI, especially over the North China Plain
(NCP). Considering carbon monoxide observations as a pollutant tracer, the
O3–CO correlation indicates that the photochemical production of ozone
from primary pollutants emitted over such large polluted regions
significantly contributes to the ozone enhancements observed in the lower
troposphere via IASI. When low-pressure systems circulate over the NCP,
stratospheric and pollution sources play a concomitant role in the ozone
enhancement. IASI's 3-D observational capability allows the areas in which
each source dominates to be determined. Moreover, the studied cut-off low
system has enough potential convective capacity to uplift pollutants (ozone
and CO) and to transport them to Japan. The increase in the enhancement ratio
of ozone to CO from 0.16 on 12 May over the North China Plain to 0.28 over
the Sea of Japan on 14 May indicates photochemical processing during the
plume transport. |
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