Publications


LARGE-SCALE HORIZONTAL MIXING IN PLANETARY-ATMOSPHERES

PHYSICS OF FLUIDS A-FLUID DYNAMICS 3 (1991) 1250-1260

RT PIERREHUMBERT


ON ATTRIBUTING GRAMMARS TO DYNAMIC-SYSTEMS

JOURNAL OF PHONETICS 18 (1990) 465-477

JB PIERREHUMBERT, RT PIERREHUMBERT


The dynamics of planetary atmospheres

Science Progress 72 (1988) 421-450

FW Taylor, PJ Gierasch, PL Read, R Hide

Current knowledge of the dynamics of the atmospheres of the planets is reviewed. This has expanded a great deal in recent years, due to the numerous space missions which have gathered new observational data. Nevertheless, there is also much which remains unknown, and many cases where new observations have simply posed additional questions of a fundamental kind. We undertake an examination of some particular examples, including the banded structure and long-lived eddies on Jupiter and Saturn, the rapid rotation of Venus' atmosphere, and the climate of Mars. -Authors


AN ESTIMATE OF MOUNTAIN DRAG DURING ALPEX FOR COMPARISON WITH NUMERICAL-MODELS

JOURNAL OF THE ATMOSPHERIC SCIENCES 45 (1988) 1949-1960

BC CARISSIMO, RT PIERREHUMBERT, HL PHAM


DOES EKMAN FRICTION SUPPRESS BAROCLINIC INSTABILITY

JOURNAL OF THE ATMOSPHERIC SCIENCES 45 (1988) 2920-2933

SJ LIN, RT PIERREHUMBERT


ON HIGH-DRAG STATES OF NONLINEAR STRATIFIED FLOW OVER AN OBSTACLE

JOURNAL OF THE ATMOSPHERIC SCIENCES 45 (1988) 63-80

JT BACMEISTER, RT PIERREHUMBERT


On the scale of baroclinic instability in deep, compressible atmospheres

Quarterly Journal of the Royal Meteorological Society 114 (1988) 421-437

PL Read

A simple model of linearized, inviscid baroclinic instability in an adiabatic, hydrostatic, compressible atmosphere of arbitrary (though finite) depth, based on the well‐known Eady model, is used to investigate the variation of growth rates and favoured horizontal length scales as functions of δ, the ratio of the model depth D to the density scale height Hs. Both geometric height coordinates (with w = 0 horizontal boundary conditions) and log‐pressure (with ω = 0 boundary conditions) are considered. For δ > 3 and a given zonal velocity scale, growth rates are significantly reduced relative to comparable instabilities in an incompressible fluid (δ = 0), and may be suppressed altogether in a laterally‐bounded channel for large enough δ at a given value of static stability. Where instability does occur, the length scales favoured are longer than for an incompressible fluid, and are generally comparable to a deformation radius based on D (rather than Hs). The relationship between these results and those obtained in comparable recent studies (which have found scales comparable to a deformation radius based on Hs to be important) is examined. Some implications for the role of baroclinic instability in the atmospheres of the major planets are also discussed. Copyright © 1988 Royal Meteorological Society


THE DYNAMICS OF PLANETARY-ATMOSPHERES

SCIENCE PROGRESS 72 (1988) 421-450

FW TAYLOR, PJ GIERASCH, PL READ, R HIDE


Finite-amplitude, neutral baroclinic eddies and mean flows in an internally heated, rotating fluid: 2. Effects of spatially varying N<sup>2</sup>

Dynamics of Atmospheres and Oceans 11 (1988) 211-264

PL Read

The analytical model of finite-amplitude, quasi-geostrophic 'free mode' baroclinic eddies and mean zonal flows in a Cartesian channel, presented recently by Read, is extended to take account of vertical variations in the buoyancy frequency N. A series of exact solutions is presented to illustrate the effect of monotonically varying static stability on the structure and properties of the flow. The analytical solutions are then compared with a corresponding series of numerical simulations of steady wave flows in a rotating fluid annulus subject to internal heating and sidewall cooling. By suitable choices of internal heating distributions and boundary conditions, several different forms of N2 profile could be obtained in the simulated flows, in which N2 was concentrated to a greater or lesser extent towards the upper boundary. The resulting steady flows exhibited strong qualitative similarities in their structure and dependence upon the form of N2(z) to that of the analytical solutions when realistic profiles of N2 were included in the latter, especially when an equivalent-barotropic component was included, although the latter component is unable to satisfy the simplest (internal jet) form of horizontal boundary condition as usually applied to Rossby waves. The relatively weak, though crucially important, forcing and dissipation processes in the annulus are examined using approximate quasi-geostrophic diagnostics of the major terms in the budget of potential enstrophy for the numerical simulations. Internal heating is found to be the major source of potential enstrophy for the mean zonal flow, solely by virtue of the variation of N2 with height, but has only a minor direct effect upon the eddy flow component. Because of the presence of critical layers in the flow, all non-linear terms (including the third-order potential enstrophy flux divergence) are found to be significant in certain regions. Some implications for the value and applicability of EP flux diagnostics are discussed. Potential enstrophy budgets for horizontal regions enclosed by geostrophic streamlines are used to shed further insight into the maintenance of the flow against 'friction', and on the form of the potential vorticity-streamfunction relationship. Some implications of the results for other systems of geophysical interest are also discussed. © 1988.


RICHARDSON CRITERIA FOR STRATIFIED VORTEX MOTIONS UNDER GRAVITY - COMMENT

PHYSICS OF FLUIDS 30 (1987) 1231-1232

SJ LIN, RT PIERREHUMBERT


EXTERNAL ROSSBY WAVES IN THE 2-LAYER MODEL

JOURNAL OF THE ATMOSPHERIC SCIENCES 44 (1987) 2924-2933

RL PANETTA, IM HELD, RT PIERREHUMBERT


Clearer circulation on Uranus

Nature 325 (1987) 197-198

PL Read


Soliton theory and Jupiter's great red spot

Nature 326 (1987) 337-338

PL Read


Universal short-wave instability of two-dimensional eddies in an inviscid fluid.

Physical review letters 57 (1986) 2157-2159

RT Pierrehumbert


Problems and Prospects in Long and Medium Range Weather Forecasting

Journal of Fluid Mechanics 163 (1986) 498-500

RT Pierrehumbert


SPATIALLY AMPLIFYING MODES OF THE CHARNEY BAROCLINIC-INSTABILITY PROBLEM

JOURNAL OF FLUID MECHANICS 170 (1986) 293-317

RT PIERREHUMBERT


DISSIPATIVE DESTABILIZATION OF EXTERNAL ROSSBY WAVES

JOURNAL OF THE ATMOSPHERIC SCIENCES 43 (1986) 388-396

IM HELD, RT PIERREHUMBERT, RL PANETTA


Remarks on a paper by Aref and Flinchem

JOURNAL OF FLUID MECHANICS 163 (1986) 21-26

RT Pierrehumbert


THE EFFECT OF LOCAL BAROCLINIC INSTABILITY ON ZONAL INHOMOGENEITIES OF VORTICITY AND TEMPERATURE

ADVANCES IN GEOPHYSICS 29 (1986) 165-182

RT PIERREHUMBERT


Super‐rotation and diffusion of axial angular momentum: II. A review of quasi‐axisymmetric models of planetary atmospheres

Quarterly Journal of the Royal Meteorological Society 112 (1986) 253-272

PL Read

The role of angular momentum quasi‐conservation in generating and maintaining axisymmetric flows characterized by a net global and/or local super‐rotation is reviewed. The conditions under which angular momentum per unit mass, m, can be diffused by Newtonian viscosity against its mean gradient in the meridional plane in a compressible, spherical fluid shell are explored in detail, and integral constraints on the form of the diffusive flux of m are derived for a steady flow. The implications of the results for simple models of planetary and stellar atmospheres are explored, with particular reference to the analogy between molecular and ‘eddy’ viscosity (as represented in mixing‐length theory), and various mixing hypotheses for eddy transfer properties. The results are relevant to zonally‐averaged models of the circulation of planetary and stellar atmospheres since, in the absence of molecular viscosity, the Eliassen—Palm flux of m must obey similar integral constraints to those applicable to the viscous flux in a purely axisymmetric system. Despite the non‐Newtonian character of realistic eddies in a baroclinic atmosphere, therefore, studies of simple axisymmetric systems with viscous diffusion can shed some useful insight into ways in which atmospheres, such as those of the earth, Venus, Titan, the Jovian planets and the sun, may acquire significant components of super‐rotation and prograde differential rotation, especially (though not exclusively) near the equator. Copyright © 1986 Royal Meteorological Society

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