A Two-Dimensional Balanced Model of Internal Frontogenesis in Geostrophic and Isentropic Coordinates
Abstract
This theses seeks to both improve and simplify the method by which upper frontogenesis may be studied. Using a two-dimensional form of the geostrophic momentum approximation in geostrophic/isentropic coordinates, our dynamic model reduces to a predictive equation for the potential pseudo-density (inverse Rossby-Ertel potential vorticity), with associated diagnostic equation for the Bernoulli function from which the wind and mass fields can be calculated. Ageostrophic motions are implicit, and vertical motions retained for the adiabatic case employed, by this choice of coordinates. Initialization of the domain incorporates a realistic vertical distribution of the mass field along with upper/lower boundaries which are either isobaric/isentropic or constant potential vorticity surfaces. Vertical wind shears such as are commonly associated with baroclinic waves are idealized and act as the forcing mechanism for frontogenesis. Major model results include the formation of upper fronts with associated wind and thermal fields which, when viewed together, are well correlated with observations of these parameters in terms of magnitude and gradient as well as their proximity to one another. Well-defined folding of the dynamic tropopause occurs in geostrophic space; thus, unlike previous balanced models, the transformation back to physical space is not required in order to produce the desired results. However, performing the coordinate transformation enhances the realism of the results.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1990
- Accession Number
- ADA227644
Entities
People
- Norman H. Mandy
Organizations
- Air Force Institute of Technology