A square splittered and unsplittered rod is placed in a turbulent boundary layer developed over a flat plate. The effect of the resulting disturbances on the local heat transfer coefficient is then studied. In both cases the square rod modifies the flow structure inside the boundary layer. As a result, a stagnation point, a jet and wake area are generated around the square rod, each making a co...

The equilibrium of a modeled windand buoyancy-driven, baroclinically unstable, ‡ow is analyzed using the transformed Eulerian-mean (TEM) approach described in Part I. Within the near-adiabatic interior of the ‡ow, Ertel potential vorticity is homogenized along mean isopycnals, a …nding readily explained using TEM theory, given the geometry of the domain. The equilibrium, zonal-mean buoyancy str...

Many studies of tornado-severe local storms outbreaks have called attention to the role of the jet stream. In fact, the jet has become an accepted part of a climatological model for tornado occurrences in the central and southern Plains. This study undertakes to verify this acceptance by statistically testing the association between 500-mb. indications of the midlatitude and subtropical jet str...

Coherent jets, such as the Jovian banded winds, are a prominent feature of rotating turbulence. Shallowwater turbulence models capture the essential mechanism of jet formation, which is systematic eddy momentum flux directed up the mean velocity gradient. Understanding how this systematic eddy flux convergence is maintained and how the mean zonal flow and the eddy field mutually adjust to produ...

the development of the dynamical core of a potential-vorticity-based atmospheric general circulation model is explored. there are some advantages of using potential vorticity (pv) as a prognostic variable in that the resulting model can give more accurate simulation of the evolution of pv, as arguably the most fundamental dynamical quantity. further, there is possibility of explicit representat...

The persistence of the southern annular mode (SAM) is studied during austral winter (June–September) and summer (December–March) using observations of the three-dimensional vorticity budget. Analysis of the relative vorticity tendency equation shows that convergence of eddy vorticity flux in the upper troposphere, coupled with a secondary circulation, constitutes a positive eddy feedback that a...

This paper studies multiple regimes and low-frequency oscillations in the Northern Hemisphere zonal-mean zonal flow in winter, using 55 years of daily observational data. The probability density function estimated in the phase space spanned by the two leading empirical orthogonal functions exhibits two distinct, statistically significant maxima. The two regimes associated with these maxima desc...

The aim of this paper is to determine how an atmosphere with enhanced mean-state baroclinity can support weaker baroclinic wave activity than an atmosphere with weak mean-state baroclinity. As a case study, a Last Glacial Maximum (LGM) model simulation previously documented to have reduced baroclinic storm activity, relative to the modern-day climate (simulated by the same model), despite havin...

The linear impulse response of axisymmetric jets is examined for a family of variable-temperature profiles typical of the potential core. The influence of jet heating, shear layer thickness, Reynolds and Mach number on the spatio-temporal stability of both axisymmetric and helical modes is investigated. The linear impulse response is retrieved from a numerical solution of the spatial eigenvalue...

It has been suggested that changes in the atmospheric circulation caused by anthropogenic forcings are highly uncertain, owing to the large natural variability intrinsic to the system. Here, to assess the statistical significance of such changes for the midlatitude, large-scale atmospheric circulation of the Southern Hemisphere, we analyze a new 40-member ensemble of integrations, from 1920 to ...