HR: 0830h
AN: A31C-0036    [PDF]
TI: The Equations of Motion in PV-coordinates
AU: * Stan, C
EM: stan@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523
AU: Randall, D A
EM: randall@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523
AB: The importance of potential vorticity (PV) for the global circulation of the atmosphere is now well recognized. This quantity captures all relevant information about balanced flows in a single scalar field, and therefore many aspects of the general circulation can be described compactly in terms of potential-vorticity dynamics. The dynamical equations governing the atmospheric flow can be transformed into a system of coordinates that uses PV as the meridional coordinate. We are exploring the utility of this coordinate for modeling the zonal-mean flow. The technique relies on the fact that PV is materially conserved in adiabatic, frictionless flow. We have constructed a shallow-water model on a sphere in which the meridional coordinate is the potential vorticity. In this model, (i) the mass flows in only one direction, parallel to the latitudinal circle on a surface of constant potential vorticity, (ii) the zonally averaged mass-weighted angular momentum changes only in response to the net form drag acting on a PV contour, (iii) in a time average or steady state the form drag is the same on all PV contours. We have also generalized the model to three dimensions, using potential temperature coordinates.
DE: 0399 General or miscellaneous
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting