Secondary Circulations on the Potential Vorticity Staircase: A Theory of Atmospheric Transport

Northwest Research Associates, Incorporated, Seattle WA

Investigators

Abstract

The goal of this project is to examine interactions between two fundamental and distinct types of atmospheric circulation: primary circulations, consisting of zonal, east-west directed jets together with their embedded Rossby waves and Rossby-wave critical layers; and the slower but persistent secondary circulations, which are driven to a large extent by the eddy mixing associated with the jets and waves of the primary circulations, and which control long-term meridional transport throughout the atmosphere. Although primary circulations drive secondary ones, the latter also modify the former though the transport both of momentum and of radiatively active chemical species, notably carbon dioxide, water vapor, and ozone. The work builds extensively on previous NSF-supported research on the "potential vorticity staircase" and the nature of atmospheric zonal jets. A key theme will involve a consideration of the influence of inhomogeneous eddy mixing on the distribution of secondary circulations in height and latitude; and, in turn, the steepening of chemical tracer and potential vorticity gradients by the differential vertical motions of the secondary circulations. Theoretical investigations into the importance of non-trivial vertical structure and the role of eddy-driven secondary circulations in the potential vorticity staircase will be complemented by applications to topical issues in stratosphere-troposphere and tropical-polar dynamical coupling and the transport of chemical tracers throughout the atmosphere.