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| Titel |
Nonlinear Interaction between Solar Tides |
| VerfasserIn |
Thomas Kessemeier, Ulrich Achatz |
| 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 |
250035542
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| Zusammenfassung |
| Atmospheric solar tides are large-scale waves driven by the absorption of solar radiation,
mainly due to water vapour and ozone, in the troposphere and stratosphere. Because tidal
amplitudes increase roughly as 1---
Ï, Ï being the density, tides play a major role in the
dynamics of the mesosphere/lower thermosphere region.
In the present work a linearised primitive equation model is used to describe the tidal signal.
We take a linear regression approach for determining optimal profiles of Rayleigh friction,
newtonian cooling and horizontal diffusion to account for interactions with small-scale
structures, mainly gravity waves, which cannot be resolved by our model. The nonlinear
interaction between stationary planetary waves and solar tides is also included. The amplitude
and phase structure of the diurnal tide is shown to be reproduced in accordance with the
state-of-the-art general circulation model HAMMONIA if we take the imaginary
parts of Rayleigh friction and newtonian cooling into consideration. The results
for the diurnal tide are shown to be further improved by adding a forcing term to
the linear model that contains nonlinear contributions to the diurnal signal from
the semidiurnal and terdiurnal tides. Corresponding analyses are also done for the
semidiurnal tide. Annual cycles for both the diurnal and the semidiurnal tides will be
discussed. |
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