CAS Seminar

Almut Gassmann

(IAP Kühlungsborn)

"A three-dimensional general balance relation for atmospheric dynamics"

Date: Wed, March 6, 2019
Time: 15:45
Place: Research I Meeting Room

Abstract: A three-dimensional general balanced solution to the governing equations of the atmosphere is given. The deviation from this balanced, or inactive, wind solution is called the active wind. For the horizontal components, this active wind is comparable to the ageostrophic wind. The vertical active wind component is similar to the isentropic displacement vertical wind. Transformed governing equations are derived as functions of the active wind components. This is also possible for the vorticity and divergence equations, respectively. It turns out that the classical balance equation is not part of the transformed divergence equation, but reflects the balanced part which had been removed. The terms on the right of the transformed equations can be scrutinized with respect to their effects on the evolution of the atmospheric state. Exemplarily, this is done for an idealized baroclinic wave in a dry atmosphere. The different terms on the right of the transformed equations and the active wind components are visualised and interpreted in their meaning. Most importantly, the newly introduced vertical active wind component allows for an analysis of the vertical motion of isentropes. The baroclinic wave development is discussed with focus on the fronts and the generation or depletion of kinetic energy. The new method allows for a unique separation of gravity waves and vortical modes. This facilitates the analysis of gravity wave generation and propagation from jets and fronts.