The TRR 181 seminar is held byDr. Georg Sebastian Völker (Goethe-Universität Frankfurt) on July 16.
Wave-Wave Interactions of Internal Gravity Waves and Their Importance in the Atmosphere
Internal gravity waves are a well known mechanism of energy transport in stratified fluids such as the atmosphere and the ocean. Their abundance and importance for various geophysical processes like ocean mixing and momentum deposition in atmospheric jets are widely accepted.
In the context of the atmosphere the background mean flow is generally of the same magnitude or stronger than the wave signal. Moreover the anelastic amplification leads to strong wave signals as the disturbances propagate in the vertical. While classical considerations of resonant wave-wave interactions of quasi-monochromatic internal gravity waves have widely neglected these effects they need to be considered when applying the same concepts to atmospheric dynamics.
In this talk the main differences in typical properties of internal gravity waves in the ocean and the atmosphere will be briefly discussed. Then a theory for triadic interactions between wave trains that are modulated by a variable mean flow is presented. Using the method of multiple scale asymptotics a weakly non-linear Boussinesq WKBJ theory for interacting gravity wave trains is considered. Consequently the wave trains are allowed to spectrally pass through resonance conditions and exchange energy when sufficiently close to resonance. Finally the results of idealized simulations in which two wave trains generate a third by passing through resonance in a sinusoidal background shear flow with various configurations are shown.