Propagation And Dissipation Of Lee Wave Energy In A Single Column Model
- 1Universität Hamburg, Institut für Meereskunde, Theoretische Ozeanographie, Hamburg, Germany (ingo.wagner@studium.uni-hamburg.de)
- 2Alfred Wegener Institut für Polar- und Meeresforschung, Bremerhaven, Germany
- 3MARUM, Universität Bremen, Bremen, Germany
When an ocean current flows over uneven topography a specific kind of in-
ternal gravity wave called lee wave is emitted. These lee waves are propagating
through the water column and can interact with the ocean currents and other
waves. They are thought to play a role in the global ocean energy cycle and
can also affect the momentum balance in the interior. The waves extract energy
from the mean flow or eddies near the bottom and then dissipate this energy
somewhere in the water column.
However, the waves can not be resolved directly in global ocean models and in
particular their vertical propagation is still largely unknown. In order to study
these waves Eden and Olbers proposed a model of the lee wave energy. In this model
the radiative transfer equation is integrated over the wavenumber space which
yields a prognostic equation of the lee wave energy. This energy equation can
then be added to an ocean model. This model includes a term for the interac-
tion with the mean flow and a dissipation term parameterizing the interaction
with the background wave field.
In this work an additional term concerning the dissipation due to critical layers
is added to the energy equation. The critical layers can occur when the back-
ground current shift the wavelength to small scales so that the waves break. For
this critical layer parameterization the vertical refraction term in the radiative
transfer equation is integrated.
The energy equation is then added to the python ocean model (pyOM) and
simulations using a single column are conducted. The key results show that the
interaction with the background wave field typically dominates the other effects.
This leads to an exponential decay of the energy away from the ocean bottom.
If the waves reach a region with a vertical velocity shear the waves can also ex-
tract energy and momentum from the current. The leads to a slight downwards
deflection of the current and also enables some critical layer dissipation. Thus
in these conditions the lee waves also lead to some dissipation and mixing in
the ocean interior far away from the bottom. The maximum dissipation near
the bottom is found to be larger than 10-8m2/s3, which is in accordance with
other simulations and observations.
How to cite: Wagner, I., Eden, C., and Olbers, D.: Propagation And Dissipation Of Lee Wave Energy In A Single Column Model, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16509, https://doi.org/10.5194/egusphere-egu23-16509, 2023.
