Publications


General Circulation of Planetary Atmospheres: Insights from Rotating Annulus and Related Experiments

Modeling Atmospheric and Oceanic Flows: Insights from Laboratory Experiments and Numerical Simulations John Wiley & Sons Ltd. (2015) 9-44

PL Read, EP Perez, IM Moroz, RMB Young


General circulation of planetary atmospheres: insights from rotating annulus and related experiments

in Modeling Atmospheric and Oceanic Flows: Insights from Laboratory Experiments and Numerical Simulations, American Geophysical Union (2014) 9-44

P Read, EP Perez, IM Moroz, R Young

This chapter focuses on the "classical" thermally driven, rotating annulus system. It reviews the current state of understanding of the rich and diverse range of flow regimes that may be exhibited in thermal annulus experiments from the viewpoint of experimental observation, numerical simulation, and fundamental theory. This includes interpretation of various empirical experimental observations in relation to both linear and weakly nonlinear baroclinic instability theory. The chapter then examines how heat is transported within the baroclinic annulus across the full range of control parameters, associated with both the boundary layer circulation and baroclinically unstable eddies. It considers the overall role of annulus experiments in the laboratory in continuing to advance understanding of the global circulation of planetary atmospheres and oceans, reviewing the current state of research on delineating circulation regimes obtained in large-scale circulation models in direct comparison with the sequences of flow regimes and transitions in the laboratory.


An experimental study of multiple zonal jet formation in rotating, thermally driven convective flows on a topographic beta-plane

Physics of Fluids American Institute of Physics 27 (2015) 085111

P Read, TNL Jacoby, PHT Rogberg, RD Wordsworth, YH Yamazaki, K Miki-Yamazaki, R Young, J Sommeria, H Didelle, S Viboud

A series of rotating, thermal convection experiments were carried out on the Coriolis platform in Grenoble, France, to investigate the formation and energetics of systems of zonal jets through nonlinear eddy/wave-zonal flow interactions on a topographic ß-plane. The latterwas produced by a combination of a rigid, conically sloping bottom and the rotational deformation of the free upper surface. Convection was driven by a system of electrical heaters laid under the (thermally conducting) sloping bottom and led to the production of intense, convective vortices. These were observed to grow in size as each experiment proceeded and led to the development of weak but clear azimuthal jet-like flows, with a radial scale that varied according to the rotation speed of the platform. Detailed analyses reveal that the kinetic energy-weighted radial wavenumber of the zonal jets, k<inf>J y</inf>, scales quite closely either with the Rhines wavenumber as k<inf>J y</inf> ≃ 2(β<inf>T</inf>/2u<inf>rms</inf>)<sup>1/2</sup>, where u<inf>rms</inf> is the rms total or eddy velocity and β<inf>T</inf> is the vorticity gradient produced by the sloping topography, or the anisotropy wavenumber as k<inf>J y</inf> ≃ 1.25(β<sup>3</sup><inf>T</inf> ε{lunate})<sup>1/5</sup>, where ε{lunate} is the upscale turbulent energy transfer rate. Jets are primarily produced by the direct quasi-linear action of horizontal Reynolds stresses produced by trains of topographic Rossby waves. The nonlinear production rate of zonal kinetic energy is found to be strongly unsteady, however, with fluctuations of order 10-100 times the amplitude of the mean production rate for all cases considered. The time scale of such fluctuations is found to scale consistently with either an inertial time scale, Τ<inf>p</inf> ~ 1.√u<inf>rms</inf> β<inf>T</inf>, or the Ekman spin-down time scale. Kinetic energy spectra show some evidence for a k<sup>-5/3</sup> inertial subrange in the isotropic component, suggestive of a classical Kolmogorov-Batchelor-Kraichnan upscale energy cascade and a steeper spectrum in the zonal mean flow, though not as steep as k<sup>-5</sup>, as anticipated for fully zonostrophic flow. This is consistent with a classification of all of these flows as marginally zonostrophic, as expected for values of the zonostrophy parameter R<inf>β</inf> ≃ 1.6-1.7, though a number of properties related to flow anisotropy were found to vary significantly and systematically within this range.


A new, fast and flexible radiative transfer method for Venus general circulation models

PLANETARY AND SPACE SCIENCE 105 (2015) 80-93

JM Mendonca, PL Read, CF Wilson, C Lee


Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses

Quarterly Journal of the Royal Meteorological Society 141 (2015) 550-562

DM Mitchell, L Montabone, S Thomson, PL Read

© 2015 Royal Meteorological Society. Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth.


The solsticial pause on Mars: 2 modelling and investigation of causes

Icarus 264 (2015) 465-477

DP Mulholland, SR Lewis, PL Read, JB Madeleine, F Forget

© 2015 Elsevier Inc. The martian solsticial pause, presented in a companion paper (. Lewis et al., 2016), was investigated further through a series of model runs using the UK version of the LMD/UK Mars Global Climate Model. It was found that the pause could not be adequately reproduced if radiatively active water ice clouds were omitted from the model. When clouds were used, along with a realistic time-dependent dust opacity distribution, a substantial minimum in near-surface transient eddy activity formed around solstice in both hemispheres. The net effect of the clouds in the model is, by altering the thermal structure of the atmosphere, to decrease the vertical shear of the westerly jet near the surface around solstice, and thus reduce baroclinic growth rates. A similar effect was seen under conditions of large dust loading, implying that northern midlatitude eddy activity will tend to become suppressed after a period of intense flushing storm formation around the northern cap edge. Suppression of baroclinic eddy generation by the barotropic component of the flow and via diabatic eddy dissipation were also investigated as possible mechanisms leading to the formation of the solsticial pause but were found not to make major contributions. Zonal variations in topography were found to be important, as their presence results in weakened transient eddies around winter solstice in both hemispheres, through modification of the near-surface flow. The zonal topographic asymmetry appears to be the primary reason for the weakness of eddy activity in the southern hemisphere relative to the northern hemisphere, and the ultimate cause of the solsticial pause in both hemispheres. The meridional topographic gradient was found to exert a much weaker influence on near-surface transient eddies.


Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses

Quarterly Journal of the Royal Meteorological Society Wiley 141 (2015) 550–562-

DM Mitchell, L Montabone, S Thomson, P Read

Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth. © 2014 The Authors.


A sea change in exoplanet climate models?

Astrobiology 14 (2014) 627-628

PL Read


On the stirring properties of the thermally-driven rotating annulus

PHYSICA D-NONLINEAR PHENOMENA 268 (2014) 50-58

RJ Keane, PL Read, GP King


A simple carbon cycle representation for economic and policy analyses

CLIMATIC CHANGE 126 (2014) 319-335

MJ Glotter, RT Pierrehumbert, JW Elliott, NJ Matteson, EJ Moyer


Short-Lived Climate Pollution

ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES, VOL 42 42 (2014) 341-+

RT Pierrehumbert


ABIOTIC OXYGEN-DOMINATED ATMOSPHERES ON TERRESTRIAL HABITABLE ZONE PLANETS

ASTROPHYSICAL JOURNAL LETTERS 785 (2014) ARTN L20

R Wordsworth, R Pierrehumbert


Characterizing exoplanets

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372 (2014)

S Miller, A Coustenis, P Read, J Tennyson


Cassini observations reveal a regime of zonostrophic macroturbulence on Jupiter

Icarus 229 (2014) 295-320

B Galperin, RMB Young, S Sukoriansky, N Dikovskaya, PL Read, AJ Lancaster, D Armstrong

In December 2000, the Cassini fly-by near Jupiter delivered high-resolution images of Jupiter's clouds over the entire planet in a band between 50°N and 50°S. Three daily-averaged two-dimensional velocity snapshots extracted from these images are used to perform spectral analysis of jovian atmospheric macroturbulence. A similar analysis is also performed on alternative data documented by Choi and Showman (Choi, D., Showman, A. [2011]. Icarus 216, 597-609), based on a different method of image processing. The inter-comparison of the products of both analyses ensures a better constraint of the spectral estimates. Both analyses reveal strong anisotropy of the kinetic energy spectrum. The zonal spectrum is very steep and most of the kinetic energy resides in slowly evolving, alternating zonal (west-east) jets, while the non-zonal, or residual spectrum obeys the Kolmogorov-Kraichnan law specific to two-dimensional turbulence in the range of the inverse energy cascade. The spectral data is used to estimate the inverse cascade rate {small element of} and the zonostrophy index Rβ for the first time. Although both datasets yield somewhat different values of {small element of}, it is estimated to be in the range 0.5-1.0×10-5m2s-3. The ensuing values of Rβ≳5 belong well in the range of zonostrophic turbulence whose threshold corresponds to Rβ≃2.5. We infer that the large-scale circulation is maintained by an anisotropic inverse energy cascade. The removal of the Great Red Spot from both datasets has no significant effect upon either the spectra or the inverse cascade rate. The spectral data are used to compute the rate of the energy exchange, W, between the non-zonal structures and the large-scale zonal flow. It is found that instantaneous values of W may exceed {small element of} by an order of magnitude. Previous numerical simulations with a barotropic model suggest that W and {small element of} attain comparable values only after averaging of W over a sufficiently long time. Near-instantaneous values of W that have been routinely used to infer the rate of the kinetic energy supply to Jupiter's zonal flow may therefore significantly overestimate {small element of}. This disparity between W and {small element of} may resolve the long-standing conundrum of an unrealistically high rate of energy transfer to the zonal flow. The meridional diffusivity Kφ in the regime of zonostrophic turbulence is given by an expression that depends on {small element of}. The value of Kφ estimated from the spectra is compared against data from the dispersion of stratospheric gases and debris resulting from the Shoemaker-Levy 9 comet and Wesley asteroid impacts in 1994 and 2009 respectively. Not only is Kφ found to be consistent with estimates for both impacts, but the eddy diffusivity found from observations appears to be scale-independent. This behaviour could be a consequence of the interaction between anisotropic turbulence and Rossby waves specific to the regime of zonostrophic macroturbulence. © 2013 Elsevier Inc.


The Mars Analysis Correction Data Assimilation (MACDA) Dataset V1.0

GEOSCIENCE DATA JOURNAL 1 (2014) 129-139

L Montabone, K Marsh, SR Lewis, PL Read, MD Smith, J Holmes, A Spiga, D Lowe, A Pamment


ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. I. ACOUSTIC AND INERTIA-GRAVITY WAVES

ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 213 (2014) ARTN 17

J Peralta, T Imamura, PL Read, D Luz, A Piccialli, MA Lopez-Valverde


ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. II. LAMB, SURFACE, AND CENTRIFUGAL WAVES

ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 213 (2014) ARTN 18

J Peralta, T Imamura, PL Read, D Luz, A Piccialli, MA Lopez-Valverde


Overview of physics results from MAST towards ITER/DEMO and the MAST Upgrade

NUCLEAR FUSION 53 (2013) ARTN 104008

H Meyer, IG Abel, RJ Akers, A Allan, SY Allan, LC Appel, O Asunta, M Barnes, NC Barratt, N Ben Ayed, JW Bradley, J Canik, P Cahyna, M Cecconello, CD Challis, IT Chapman, D Ciric, G Colyer, NJ Conway, M Cox, BJ Crowley, SC Cowley, G Cunningham, A Danilov, A Darke, MFM De Bock, G De Temmerman, RO Dendy, P Denner, D Dickinson, AY Dnestrovsky, Y Dnestrovsky, MD Driscoll, B Dudson, D Dunai, M Dunstan, P Dura, S Elmore, AR Field, G Fishpool, S Freethy, W Fundamenski, L Garzotti, YC Ghim, KJ Gibson, MP Gryaznevich, J Harrison, E Havlickova, NC Hawkes, WW Heidbrink, TC Hender, E Highcock, D Higgins, P Hill, B Hnat, MJ Hole, J Horacek, DF Howell, K Imada, O Jones, E Kaveeva, D Keeling, A Kirk, M Kocan, RJ Lake, M Lehnen, HJ Leggate, Y Liang, MK Lilley, SW Lisgo, YQ Liu, B Lloyd, GP Maddison, J Mailloux, R Martin, GJ McArdle, KG McClements, B McMillan, C Michael, F Militello, P Molchanov, S Mordijck, T Morgan, AW Morris, DG Muir, E Nardon, V Naulin, G Naylor, AH Nielsen, MR O'Brien, T O'Gorman, S Pamela, FI Parra, A Patel, SD Pinches, MN Price, CM Roach, JR Robinson, M Romanelli, V Rozhansky, S Saarelma, S Sangaroon, A Saveliev, R Scannell, J Seidl, SE Sharapov, AA Schekochihin, V Shevchenko, S Shibaev, D Stork, J Storrs, A Sykes, GJ Tallents, P Tamain, D Taylor, D Temple, N Thomas-Davies, A Thornton, MR Turnyanskiy, M Valovic, RGL Vann, E Verwichte, P Voskoboynikov, G Voss, SEV Warder, HR Wilson, I Wodniak, S Zoletnik, R Zagorski, MAST Team, NBI Team


WATER LOSS FROM TERRESTRIAL PLANETS WITH CO2-RICH ATMOSPHERES

ASTROPHYSICAL JOURNAL 778 (2013) ARTN 154

RD Wordsworth, RT Pierrehumbert


Nonlinear Phenomena in Atmospheric and Oceanic Sciences

Springer, 2013

G Carnevale, RT Pierrehumbert

This IMA Volume in Mathematics and its Applications NONLINEAR PHENOMENA IN ATMOSPHERIC AND OCEANIC SCIENCES is based on the proceedings of a workshop which was an integral part of the 1989-90 IMA program on &quot;Dynamical Systems and their ...

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