Warm conveyor belts (WCBs) are the main ascending air masses within extratropical cyclones. They often exhibit strong condensation and precipitation, associated with ascent on large scales or embedded convection. Most of the air outflows into the upper troposphere as part of a ridge. Such ridges are an integral part of Rossby waves propagating along the tropopause and are identified with a nega...

We discuss and compare different approaches to calculating the dynamics of anisotropic flow structure formation in quasi two-dimensional turbulence based on potential vorticity (PV) transport in real space. The general structure of the PV flux in the relaxation processes is deduced non-perturbatively. The transport coefficients of the PV flux are then systematically calculated using perturbatio...

Two-dimensional unsteady incompressible flows in which the potential vorticity (PV) plays a key role are examined in this study, through the development of the evolution equation for the PV gradient. For the case where the PV is conserved, precise statements concerning topologyconservation are presented. While establishing some intuitively well-known results (the numbers of eddies and saddles i...

Mid-tropospheric frontogenesis is investigated for a case study in which special three-hourly rawinsonde data are available. Isentropic analyses are generated by objective means. Detailed machine isentropic trajectories lead to the three-dimensional description of the velocity field in space and time accompanying the frontogenesis. Ertel potential vorticity calculations serve as a check on traj...

Precipitating versions of the quasi-geostrophic (QG) equations are derived systematically, starting from the equations of a cloud-resolving model. The presence of phase changes of water from vapor to liquid and vice versa leads to important differences from the dry QG case. The precipitating QG (PQG) equations, in their simplest form, have two variables to describe the full system: a potential ...

Surface cyclone tracks are investigated in the context of moist potential vorticity (MPV). A prognostic equation of surface absolute vorticity is derived which provides a basis for using negative MPV (NMPV) in the troposphere as an alternative approach to track surface cyclones. An observed case study of explosive lee cyclogenesis is performed to test the effectiveness of the MPV approach. It i...

While it has been recognized for some time that isentropic coordinates provide a convenient framework for theories of the global circulation of the atmosphere, the role of boundary effects in the zonal momentum balance and in potential vorticity dynamics on isentropes that intersect the surface has remained unclear. Here, a balance equation is derived that describes the temporal and zonal mean ...

Several different kinds of accurate potential vorticity (PV) inversion operators, and the associated balanced models, are tested for the shallow water equations on a hemisphere in an attempt to approach the ultimate limitations of the balance, inversion, and slow-manifold concepts. The accuracies achieved are far higher than for standard balanced models accurate to one or two orders in Rossby n...

Recently F. Huang [Commun. Theor. Phys. 42 (2004) 903] and X. Tang and P.K. Shukla [Commun. Theor. Phys. 49 (2008) 229] investigated symmetry properties of the barotropic potential vorticity equation without forcing and dissipation on the beta-plane. This equation is governed by two dimensionless parameters, F and β, representing the ratio of the characteristic length scale to the Rossby radius...