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| Titel |
Borneo vortex and mesoscale convective rainfall |
| VerfasserIn |
S. Koseki, T.-Y. Koh, C.-K. Teo |
| 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 ; 14, no. 9 ; Nr. 14, no. 9 (2014-05-09), S.4539-4562 |
| Datensatznummer |
250118688
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| Publikation (Nr.) |
 copernicus.org/acp-14-4539-2014.pdf |
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| Zusammenfassung |
| We have investigated how the Borneo vortex develops over the equatorial
South China Sea under cold surge conditions in December during the Asian
winter monsoon. Composite analysis using reanalysis and satellite data sets
has revealed that absolute vorticity and water vapour are transported by
strong cold surges from upstream of the South China Sea to around the
Equator. Rainfall is correspondingly enhanced over the equatorial South
China Sea. A semi-idealized experiment reproduced the Borneo vortex over the
equatorial South China Sea during a "perpetual" cold surge. The Borneo
vortex is manifested as a meso-α cyclone with a comma-shaped
rainband in the northeast sector of the cyclone. Vorticity budget analysis
showed that the growth/maintenance of the meso-α cyclone was
achieved mainly by the vortex stretching. This vortex stretching is due to
the upward motion forced by the latent heat release around the cyclone
centre. The comma-shaped rainband consists of clusters of meso-β-scale rainfall cells. The intense rainfall in the comma head (comma tail) is
generated by the confluence of the warmer and wetter cyclonic easterly flow
(cyclonic southeasterly flow) and the cooler and drier northeasterly surge
in the northwestern (northeastern) sector of the cyclone. Intense upward
motion and heavy rainfall resulted due to the low-level convergence and the
favourable thermodynamic profile at the confluence zone. In particular, the
convergence in the northwestern sector is responsible for maintenance of the
meso-α cyclone system. At both meso-α and meso-β
scales, the convergence is ultimately caused by the deviatoric strain in the
confluence wind pattern but is significantly self-enhanced by the nonlinear dynamics. |
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