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| Titel |
Relative dispersion in the atmosphere |
| VerfasserIn |
Joe LaCasce, Lise Graff, Sigmund Guttu |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091626
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| Publikation (Nr.) |
 EGU/EGU2014-5927.pdf |
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| Zusammenfassung |
| The relative dispersion of pairs of particles in flows is of central
importance when describing environmental dispersion, for example of
volcanic ash. Atmospheric relative dispersion was examined previously
in two balloon experiments in the Southern Hemisphere (the EOLE and
TWERLE experiments). In both cases, the dispersion at scales below
1000 km grew exponentially in time, indicating the kinetic energy
spectrum is steep. Subsequent analyses suggested though that the
dispersion had a power law dependence on time, implying a shallower
kinetic energy spectrum. The results from studies employing synthetic
particles advected by reanalysis winds are similarly inconsistent,
with indications of exponential growth in some cases and power law
growth in others.
Here we use a different statistic---the probability density function
(PDF) of pair displacements---to study dispersion the dispersion
of large numbers of synthetic particles, advected by ERA-Interim
reanalysis winds. The particles were deployed in the troposphere and
stratosphere, both in the tropics and the extra-tropics. We examine
the PDFs for the different deployments and compare them to analytical
expressions derived for different turbulent inertial ranges. In line
with the earlier balloon experiments, the results indicate exponential
growth at the sub-deformation (1000 km) scales. At larger scales, the
dispersion is anisotropic (predominantly zonal) and pair motion
becomes decorrelated. Structure functions calculated from the wind
data are in line with these conclusions. |
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