Frontogenesis in an Advective Mixed Layer Model.
Abstract
Through an analysis of a more dimensional extension of the bulk mixed layer model of Kraus and Tuner (1967) it is shown how even under spatially uniform atmospheric conditions an initially smooth horizontal temperature gradient in the surface mixed layer can still develop into a front. Essential for it is the notion that the net downward heat flux at the air-water interface is related to the difference between the mixed layer temperature T and an apparent atmospheric temperature TA (Hanley, 1971) so that the initial horizontal gradient in T corresponds to a horizontal variation in the surface buoyancy flux. As a result also the mixed layer depth differs from place to place. Depending on the direction of the wind driven transport this produces either a steepening or a flattening of the initial temperature profile. A lower bound condition for the initial horizontal advective heat flux is derived in terms of the initial surface heat flux, the stirring by the wind and the time rate of change of the apparent atmospheric temperature. If that condition is satisfied a front develops. If not, then frontogenesis is prevented by the damping effect of the local atmospheric heating. It is shown that the condition can be satisfied on the scales of lakes (or small seas) and in near equatorial oceanic regions. Mathematically the problem boils down to a first order quasilinear hyperbolic partial differential equation that is solved exactly by the method of characteristics. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1982
- Accession Number
- ADA124350
Entities
People
- Will P. M. De Ruijter
Organizations
- University of Wisconsin–Madison