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| Titel |
High-frequency processes and the generation of turbulence at thermal fronts |
| VerfasserIn |
Martina Preusse, Frank Peeters, Andreas Lorke |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033201
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| Zusammenfassung |
| High-resolution thermistor chain observations in the interior thermocline of stratified Lake Constance reveal a temporally highly variable occurrence of large-scale overturns (> 1 m). The overturns are associated with various high-frequency processes such as large Kelvin-Helmholtz billows, solitary waves and second mode waves. These high-frequency processes accompany steep thermal fronts resulting from the steepening of a basin-scale internal Kelvin-wave. The occurrence of overturns is therefore periodically coupled to the passage of the basin-scale seiche. The number of overturns increases with the amplitude of the low-frequency wave. Average values of turbulence and mixing corresponding to a single Kelvin-wave cycle are highly variable, as is the occurrence of a specific high-frequency process. Distributions of dissipation rates and eddy diffusivities depend on the actual high-frequency process. The generation of overturns at the steep fronts via the various high-frequency processes was observed between 40 and 50 m above ground suggesting that the collapse of overturns on average leads to a significant amount of turbulence and mixing in the thermocline outside the bottom boundary layer. |
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