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| Titel |
Ozone reservoir layers in a coastal environment – a case study in southern Taiwan |
| VerfasserIn |
C.-H. Lin, Y.-L. Wu, C.-H. Lai |
| 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. 9 ; Nr. 10, no. 9 (2010-05-12), S.4439-4452 |
| Datensatznummer |
250008437
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| Publikation (Nr.) |
 copernicus.org/acp-10-4439-2010.pdf |
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| Zusammenfassung |
| The air layer between the nocturnal boundary layer and the top of the daily
mixing layer in an ozone-polluted area is known to serve as an ozone
reservoir since the ozone that is produced in the mixing layer on the
preceding day is effectively preserved throughout the night in the air
layer. Ozone reservoir layers existing at night can enhance the accumulation
of surface ozone on the following day. However, our knowledge of the
characteristics of ozone reservoir layers and their effects on the daily
ozone accumulations is limited. In this work, ozone reservoir layers were
experimentally investigated at a coastal, near-mountain site in southern
Taiwan, 30 km away from the coastline. Tethered ozone soundings were
performed to obtain vertical profiles of ozone and meteorological variables
during a four-day ozone episode in November 2006. Observation-based methods
are adopted to evaluate the effects of the ozone reservoir layers on the
surface ozone accumulation during the four-day ozone episode. Ozone
reservoir layers were found to develop every evening with a depth of
1200–1400 m. Ozone concentrations within the reservoir layers reached over
140 parts per billion (ppb). From each evening to midnight, the size of the
ozone reservoir layer and the ozone concentration inside dramatically
changed. As a result, a concentrated, elevated ozone reservoir layer formed
with a depth of 400 m at 800–1200 m every midnight. For the rest of each
night, the elevated ozone reservoir layer gradually descended until it
reached 500–900 m in the next morning. The observed ozone reservoir layer is
formed by the invasion of a cool, marine air mass into a relatively warm,
ozone-rich mixing layer in the evening. The descending is related to
nocturnal coastal subsidence as well. The ozone concentration at the study
site was maximal at 15:00–17:00 LT daily because of the addition of the daily
produced ozone on the preceding day. The rate of increase of surface ozone
concentration due to the downward mixing of the ozone in the ozone reservoir
layers can be as high as 12–24 ppb/h in the late morning. The contribution
of the ozone carried over from the preceding day can be 60–85 ppb, which
contributes over 50% to the daily ozone pollution as compared with ozone
produced on the study day. |
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