Publications


Turbulence, waves, and jets in a differentially heated rotating annulus experiment

PHYSICS OF FLUIDS 20 (2008) ARTN 126602

RD Wordsworth, PL Read, YH Yamazaki


Axisymmetric, nearly inviscid circulations in non-condensing radiative-convective atmospheres

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 134 (2008) 1269-1285

R Caballero, RT Pierrehumbert, JL Mitchell


Intense polar temperature inversion in the middle atmosphere on Mars

Nature Geoscience 1 (2008) 745-749

DJ McCleese, JT Schofield, FW Taylor, WA Abdou, O Aharonson, D Banfield, SB Calcutt, NG Heavens, PGJ Irwin, DM Kass, A Kleinböhl, WG Lawson, CB Leovy, SR Lewis, DA Paige, PL Read, MI Richardson, N Teanby, RW Zurek

Current understanding of weather, climate and global atmospheric circulation on Mars is incomplete, in particular at altitudes above about 30 km. General circulation models for Mars are similar to those developed for weather and climate forecasting on Earth and require more martian observations to allow testing and model improvements. However, the available measurements of martian atmospheric temperatures, winds, water vapour and airborne dust are generally restricted to the region close to the surface and lack the vertical resolution and global coverage that is necessary to shed light on the dynamics of Mars middle atmosphere at altitudes between 30 and 80 km (ref.7). Here we report high-resolution observations from the Mars Climate Sounder instrument on the Mars Reconnaissance Orbiter. These observations show an intense warming of the middle atmosphere over the south polar region in winter that is at least 10-20 K warmer than predicted by current model simulations. To explain this finding, we suggest that the atmospheric downwelling circulation over the pole, which is part of the equator-to-pole Hadley circulation, may be as much as 50 more vigorous than expected, with consequences for the cycles of water, dust and CO"2 that regulate the present-day climate on Mars. © 2008 Macmillan Publishers Limited.


Flow transitions resembling bifurcations of the logistic map in simulations of the baroclinic rotating annulus

Physica D Elsevier 237 (2008) 2251-2262

RMB Young, PL Read

We present evidence for a sequence of bifurcations in simulations of the differentially heated baroclinic rotating annulus, similar to bifurcations of the logistic map. The Met. Office / Oxford Rotating Annulus Laboratory Simulation (MORALS) code is used to construct a detailed numerical regime diagram for the annulus, and the distribution of regimes in parameter space is discussed. The bifurcations are observed in a sequence of runs at high temperature forcing, identified by Poincare sections of the dominant temperature mode amplitude time series. Higher order return maps and predictions using quadratic fits to the data are used to verify this result, and Lyapunov exponents are calculated to identify and quantify the chaotic parts of the sequence. (c) 2008 Elsevier B.V. All rights reserved.


Erratum: "Dynamics of convectively driven banded jets in the laboratory" (Journal of the Atmospheric Sciences (2007))

Journal of the Atmospheric Sciences 65 (2008) 287-

PL Read, YH Yamazaki, SR Lewis, PD Williams, R Wordsworth, K Miki-Yamazaki, J Sommeria, H Didelle, AM Fincham


Direct numerical simulation of transitions towards structural vacillation in an air-filled, rotating, baroclinic annulus

PHYSICS OF FLUIDS 20 (2008) ARTN 044107

PL Read, P Maubert, A Randriamampianina, W-G Fruh


Tubulence, waves, and jets in a differentially heated rotating annulus experiment

Physics of Fluids 20 (2008)

RD Wordsworth, PL Read, YH Yamazaki

We report an analog laboratory study of planetary-scale turbulence and jet formation. A rotating annulus was cooled and heated at its inner and outer walls, respectively, causing baroclinic instability to develop in the fluid inside. At high rotation rates and low temperature differences, the flow became chaotic and ultimately fully turbulent. The inclusion of sloping top and bottom boundaries caused turbulent eddies to behave like planetary waves at large scales, and eddy interaction with the zonal flow then led to the formation of several alternating jets at mid-depth. The jets did not scale with the Rhines length, and spectral analysis of the flow indicated a distinct separation between jets and eddies in wavenumber space, with direct energy transfer occurring nonlocally between them. Our results suggest that the traditional "turbulent cascade" picture of zonal jet formation may be an inappropriate one in the geophysically important case of large-scale flows forced by differential solar heating.


Recurrence analysis of quasiperiodicity in experimental fluid data

EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS 164 (2008) 23-33

Y Zou, M Thiel, MC Romano, PL Read, J Kurths


Inertia-Gravity Waves Emitted from Balanced Flow: Observations, Properties, and Consequences

JOURNAL OF THE ATMOSPHERIC SCIENCES 65 (2008) 3543-3556

PD Williams, TWN Haine, PL Read


Mars Climate Sounder: An investigation of thermal and water vapor structure, dust and condensate distributions in the atmosphere, and energy balance of the polar regions

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 112 (2007) ARTN E05S06

DJ McCleese, JT Schofield, FW Taylor, SB Calcutt, MC Foote, DM Kass, CB Leovy, DA Paige, PL Read, RW Zurek


On the relative humidity of the atmosphere

in The Global Circulation of the Atmosphere, Princeton University Press (2007) 6

RT Pierrehumbert


DNS of Structural Vacillation in the transition to geostrophic turbulence

Advances in Turbulence XI - Proceedings of the 11th EUROMECH European Turbulence Conference (2007) 432-434

WG Früh, P Maubert, PL Read, A Randriamampianina

The onset of small-scale fluctuations around a steady convection pattern in a rotating baroclinic annulus filled with air is investigated using Direct Numerical Simulations (DNS). In previous laboratory experiments of baroclinic waves, such fluctuations have been associated with Structural Vacillation which is regarded as the first step in the transition to fully-developed geostrophic turbulence. Here we present an analysis which focusses on the small-scale features.


Mars Climate Sounder: An investigation of thermal and water vapor structure, dust and condensate distributions in the atmosphere, and energy balance of the polar regions

Journal of Geophysical Research E: Planets 112 (2007)

DJ McCleese, JT Schofield, FW Taylor, SB Calcutt, MC Foote, DM Kass, CB Leovy, DA Paige, PL Read, RW Zurek

Against a backdrop of intensive exploration of the Martian surface environment, intehded to lead to human exploration, some aspects of the modern climate and the meteorology of Mars remain relatively unexplored. In particular, there is a need for detailed measurements of the vertical profiles of atmospheric temperature, water vapor, dust, and condensates to understand the intricately related processes upon which the surface conditions, and those encountered during descent by landers, depend. The most important of these missing data are accurate and extensive temperature measurements with high vertical resolution. The Mars Climate Sounder experiment on the 2005 Mars Reconnaissance Orbiter, described here, is the latest attempt to characterize the Martian atmosphere with the sort of coverage and precision achieved by terrestrial weather satellites. If successful, it is expected to lead to corresponding improvements in our understanding of meteorological phenomena and to enable improved general circulation models of the Martian atmosphere for climate studies on a range of timescales. Copyright 2007 by the American Geophysical Union.


Superrotation in a Venus general circulation model

Journal of Geophysical Research E: Planets 112 (2007)

C Lee, SR Lewis, PL Read

A superrotating atmosphere with equatorial winds of ∼35 m s-1 is simulated using a simplified Venus general circulation model (GCM). The equatorial superrotation in the model atmosphere is maintained by barotropic instabilities in the midlatitude jets which transport angular momentum toward the equator. The midlatitude jets are maintained by the mean meridional circulation, and the momentum transporting waves are qualitatively similar to observed midlatitude waves; an equatorial Kelvin wave is also present in the atmosphere. The GCM is forced by linearized cooling and friction parameterizations, with hyperdiffusion and a polar Fourier filter to maintain numerical stability. Atmospheric superrotation is a robust feature of the model and is spontaneously produced without specific tuning. A strong meridional circulation develops in the form of a single Hadley cell, extending from the equator to the pole in both hemispheres, and from the surface to 50 km altitude. The zonal jets produced by this circulation reach 45 m s-1 at 60 km, with peak winds of 35 m s-1 at the equator. A warm pole and cold collar are also found in the GCM, caused by adiabatic warming in the mean meridional circulation. Wave frequencies and zonal wind speeds are smaller than in observations by cloud tracking but are consistent with a Doppler shifting by wind speeds in the generating region of each wave. Magnitudes of polar temperature anomalies are smaller than the observed features, suggesting dynamical processes alone may not be sufficient to maintain the large observed temperature contrasts at the magnitudes and periods found in this GCM. Copyright 2007 by the American Geophysical Union.


Superrotation in a Venus general circulation model

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 112 (2007) ARTN E04S11

C Lee, SR Lewis, PL Read


Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data

GEOPHYSICAL RESEARCH LETTERS 34 (2007) ARTN L17812

H Brogniez, RT Pierrehumbert


Investigating plausible mechanisms to trigger a deglaciation from a hard snowball Earth

COMPTES RENDUS GEOSCIENCE 339 (2007) 274-287

G Le Hir, G Ramstein, Y Donnadieu, RT Pierrehumbert


An ocean of air: A natural history of the atmosphere

NATURE 447 (2007) 911-911

RT Pierrehumbert


Baroclinic waves in an air-filled thermally driven rotating annulus.

Phys Rev E Stat Nonlin Soft Matter Phys 75 (2007) 026301-

AA Castrejón-Pita, PL Read

In this study an experimental investigation of baroclinic waves in air in a differentially heated rotating annulus is presented. Air has a Prandtl number of 0.707, which falls within a previously unexplored region of parameter space for baroclinic instability. The flow regimes encountered include steady waves, periodic amplitude vacillations, modulated amplitude vacillations, and either monochromatic or mixed wave number weak waves, the latter being characterized by having amplitudes less than 5% of the applied temperature contrast. The distribution of these flow regimes in parameter space are presented in a regime diagram. It was found that the progression of transitions between different regimes is, as predicted by recent numerical modeling results, in the opposite sense to that usually found in experiments with high Prandtl number liquids. No hysteresis in the flow type, with respect to variations in the rotation rate, was found in this investigation.


Assimilation of thermal emission spectrometer atmospheric data during the Mars Global Surveyor aerobraking period

ICARUS 192 (2007) 327-347

SR Lewis, PL Read, BJ Conrath, JC Pearl, MD Smith

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