Publications


Introduction

in , 105 (2011) 113-116

J Brindley, P Read, J Gibbon, A Soward


Diversity of planetary atmospheric circulations and climates in a simplified general circulation model

Proceedings of the International Astronomical Union 8 (2012) 297-302

Y Wang, P Read

The parametric dependence of terrestrial planetary atmospheric circulations and climates on characteristic parameters is studied. A simplified general circulation model - PUMA is employed to investigate the dynamic effects of planetary rotation rate and equator-to-pole temperature difference on the circulation and climate of terrestrial planetary atmospheres. Five different types of circulation regime are identified by mapping the experimental results in a 2-D parameter space defined by thermal Rossby number and frictional Taylor number. The effect of the transfer and redistribution of radiative energy is studied by building up a new two-band semi-gray radiative-convective scheme, which is capable of modelling greenhouse and anti-greenhouse effects while keeping the tunable parameters as few as possible. The results will provide insights into predicting the habitability of terrestrial exoplanets. Copyright © International Astronomical Union 2014.


Dynamics and circulation regimes of terrestrial planets

PLANETARY AND SPACE SCIENCE 59 (2011) 900-914

PL Read


Ion heat transport studies in JET

Plasma Physics and Controlled Fusion 53 (2011)

P Mantica, C Angioni, B Baiocchi, M Baruzzo, MNA Beurskens, JPS Bizarro, RV Budny, P Buratti, A Casati, C Challis, J Citrin, G Colyer, F Crisanti, ACA Figueiredo, L Frassinetti, C Giroud, N Hawkes, J Hobirk, E Joffrin, T Johnson, E Lerche, P Migliano, V Naulin, AG Peeters, G Rewoldt, F Ryter, A Salmi, R Sartori, C Sozzi, G Staebler, D Strintzi, T Tala, M Tsalas, D Van Eester, T Versloot, PC DeVries, J Weiland

Detailed experimental studies of ion heat transport have been carried out in JET exploiting the upgrade of active charge exchange spectroscopy and the availability of multi-frequency ion cyclotron resonance heating with 3He minority. The determination of ion temperature gradient (ITG) threshold and ion stiffness offers unique opportunities for validation of the well-established theory of ITG driven modes. Ion stiffness is observed to decrease strongly in the presence of toroidal rotation when the magnetic shear is sufficiently low. This effect is dominant with respect to the well-known ω E×B threshold up-shift and plays a major role in enhancing core confinement in hybrid regimes and ion internal transport barriers. The effects of T e/T i and s/q on ion threshold are found rather weak in the domain explored. Quasi-linear fluid/gyro-fluid and linear/non-linear gyro-kinetic simulations have been carried out. Whilst threshold predictions show good match with experimental observations, some significant discrepancies are found on the stiffness behaviour. © 2011 IOP Publishing Ltd.


A key to improved ion core confinement in the JET tokamak: Ion stiffness mitigation due to combined plasma rotation and low magnetic shear

Physical Review Letters 107 (2011)

P Mantica, C Angioni, C Challis, G Colyer, L Frassinetti, N Hawkes, T Johnson, M Tsalas, PC Devries, J Weiland, B Baiocchi, MNA Beurskens, ACA Figueiredo, C Giroud, J Hobirk, E Joffrin, E Lerche, V Naulin, AG Peeters, A Salmi, C Sozzi, D Strintzi, G Staebler, T Tala, D Van Eester, T Versloot

New transport experiments on JET indicate that ion stiffness mitigation in the core of a rotating plasma, as described by Mantica et al. [Phys. Rev. Lett. 102, 175002 (2009)PRLTAO0031-900710.1103/PhysRevLett.102.175002] results from the combined effect of high rotational shear and low magnetic shear. The observations have important implications for the understanding of improved ion core confinement in advanced tokamak scenarios. Simulations using quasilinear fluid and gyrofluid models show features of stiffness mitigation, while nonlinear gyrokinetic simulations do not. The JET experiments indicate that advanced tokamak scenarios in future devices will require sufficient rotational shear and the capability of q profile manipulation. © 2011 American Physical Society.


A laboratory study of global-scale wave interactions in baroclinic flow with topography I: multiple flow regimes

GEOPHYSICAL AND ASTROPHYSICAL FLUID DYNAMICS 105 (2011) PII 934802668

PL Read, SH Risch


Generation of inertia-gravity waves in the rotating thermal annulus by a localised boundary layer instability

Geophys. Astrophys. Fluid Dyn. Taylor & Francis Ltd 105 (2011) 161-181

TNL Jacoby, PL Read, PD Williams, RMB Young

Waves with periods shorter than the inertial period exist in the atmosphere (as inertia-gravity waves) and in the oceans (as Poincare and internal gravity waves). Such waves owe their origin to various mechanisms, but of particular interest are those arising either from local secondary instabilities or spontaneous emission due to loss of balance. These phenomena have been studied in the laboratory, both in the mechanically-forced and the thermally-forced rotating annulus. Their generation mechanisms, especially in the latter system, have not yet been fully understood, however. Here we examine short period waves in a numerical model of the rotating thermal annulus, and show how the results are consistent with those from earlier laboratory experiments. We then show how these waves are consistent with being inertia-gravity waves generated by a localised instability within the thermal boundary layer, the location of which is determined by regions of strong shear and downwelling at certain points within a large-scale baroclinic wave flow. The resulting instability launches small-scale inertia-gravity waves into the geostrophic interior of the flow. Their behaviour is captured in fully nonlinear numerical simulations in a finite-difference, 3D Boussinesq Navier-Stokes model. Such a mechanism has many similarities with those responsible for launching small- and meso-scale inertia-gravity waves in the atmosphere from fronts and local convection.


Infrared Radiation and Planetary Temperature

PHYSICS OF SUSTAINABLE ENERGY II: USING ENERGY EFFICIENTLY AND PRODUCING IT RENEWABLY 1401 (2011)

RT Pierrehumbert


Bifurcations leading to summer Arctic sea ice loss

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 116 (2011) ARTN D19120

DS Abbot, M Silber, RT Pierrehumbert


HYDROGEN GREENHOUSE PLANETS BEYOND THE HABITABLE ZONE

ASTROPHYSICAL JOURNAL LETTERS 734 (2011) ARTN L13

R Pierrehumbert, E Gaidos


Thermal structure and dynamics of Saturn's northern springtime disturbance.

Science 332 (2011) 1413-1417

LN Fletcher, BE Hesman, PGJ Irwin, KH Baines, TW Momary, A Sanchez-Lavega, FM Flasar, PL Read, GS Orton, A Simon-Miller, R Hueso, GL Bjoraker, A Mamoutkine, T del Rio-Gaztelurrutia, JM Gomez, B Buratti, RN Clark, PD Nicholson, C Sotin

Saturn's slow seasonal evolution was disrupted in 2010-2011 by the eruption of a bright storm in its northern spring hemisphere. Thermal infrared spectroscopy showed that within a month, the resulting planetary-scale disturbance had generated intense perturbations of atmospheric temperatures, winds, and composition between 20° and 50°N over an entire hemisphere (140,000 kilometers). The tropospheric storm cell produced effects that penetrated hundreds of kilometers into Saturn's stratosphere (to the 1-millibar region). Stratospheric subsidence at the edges of the disturbance produced "beacons" of infrared emission and longitudinal temperature contrasts of 16 kelvin. The disturbance substantially altered atmospheric circulation, transporting material vertically over great distances, modifying stratospheric zonal jets, exciting wave activity and turbulence, and generating a new cold anticyclonic oval in the center of the disturbance at 41°N.


Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia

National Academies Press, 2011

COSTFAGG Concentrations, BOASA Climate, DOEAL Studies, NR Council

The book quantifies the outcomes of different stabilization targets for greenhouse gas concentrations using analyses and information drawn from the scientific literature.


Erratum to "Flow transitions resembling bifurcations of the logistic map in simulations of the baroclinic rotating annulus" [Physica D 237 (2008) 2251-2262] (DOI:10.1016/j.physd.2008.02.014)

Physica D: Nonlinear Phenomena (2011)

RMB Young, PL Read


Infrared radiation and planetary temperature

PHYSICS TODAY 64 (2011) 33-38

RT Pierrehumbert


Plasma rotation and transport in MAST spherical tokamak

Nuclear Fusion 51 (2011)

AR Field, C Michael, RJ Akers, J Candy, G Colyer, W Guttenfelder, YC Ghim, CM Roach, S Saarelma

The formation of internal transport barriers (ITBs) is investigated in MAST spherical tokamak plasmas. The relative importance of equilibrium flow shear and magnetic shear in their formation and evolution is investigated using data from high-resolution kinetic- and q-profile diagnostics. In L-mode plasmas, with co-current directed NBI heating, ITBs in the momentum and ion thermal channels form in the negative shear region just inside qmin. In the ITB region the anomalous ion thermal transport is suppressed, with ion thermal transport close to the neo-classical level, although the electron transport remains anomalous. Linear stability analysis with the gyro-kinetic code GS2 shows that all electrostatic micro-instabilities are stable in the negative magnetic shear region in the core, both with and without flow shear. Outside the ITB, in the region of positive magnetic shear and relatively weak flow shear, electrostatic micro-instabilities become unstable over a wide range of wave numbers. Flow shear reduces the linear growth rates of low-k modes but suppression of ITG modes is incomplete, which is consistent with the observed anomalous ion transport in this region; however, flow shear has little impact on growth rates of high-k, electron-scale modes. With counter-NBI ITBs of greater radial extent form outside qmin due to the broader profile of E × B flow shear produced by the greater prompt fast-ion loss torque. © 2011 IAEA, Vienna.


Sea glacier flow and dust transport on Snowball Earth

GEOPHYSICAL RESEARCH LETTERS 38 (2011) ARTN L17501

D Li, RT Pierrehumbert


THE MARTIAN ATMOSPHERIC BOUNDARY LAYER

REVIEWS OF GEOPHYSICS 49 (2011) ARTN RG3005

A Petrosyan, B Galperin, SE Larsen, SR Lewis, A Maeaettaenen, PL Read, N Renno, LPHT Rogberg, H Savijarvi, T Siili, A Spiga, A Toigo, L Vazquez


Some fine points on radiative forcing Reply

PHYSICS TODAY 64 (2011) 12-12

RT Pierrehumbert


Overview of physics results from MAST

Nuclear Fusion 51 (2011)

B Lloyd, RJ Akers, F Alladio, S Allan, LC Appel, M Barnes, NC Barratt, N Ben Ayed, BN Breizman, M Cecconello, CD Challis, IT Chapman, D Ciric, G Colyer, JW Connor, NJ Conway, M Cox, SC Cowley, G Cunningham, A Darke, M De Bock, E Delchambre, G De Temmerman, RO Dendy, P Denner, MD Driscoll, B Dudson, D Dunai, M Dunstan, S Elmore, AR Field, G Fishpool, S Freethy, L Garzotti, KJ Gibson, MP Gryaznevich, W Guttenfelder, J Harrison, RJ Hastie, NC Hawkes, TC Hender, B Hnat, DF Howell, MD Hua, A Hubbard, G Huysmans, D Keeling, YC Kim, A Kirk, Y Liang, MK Lilley, M Lisak, S Lisgo, YQ Liu, GP Maddison, R Maingi, SJ Manhood, R Martin, GJ McArdle, J McCone, H Meyer, C Michael, S Mordijck, T Morgan, AW Morris, DG Muir, E Nardon, G Naylor, MR O'Brien, T O'Gorman, J Pláeník, A Patel, SD Pinches, MN Price, CM Roach, V Rozhansky, S Saarelma, SA Sabbagh, A Saveliev, R Scannell, SE Sharapov, V Shevchenko, S Shibaev, D Stork, J Storrs, W Suttrop, A Sykes, P Tamain, D Taylor, D Temple, N Thomas-Davies, A Thornton, MR Turnyanskiy, M Valovic, RGL Vann, G Voss, MJ Walsh, SEV Warder, HR Wilson, M Windridge

Major developments on the Mega Amp Spherical Tokamak (MAST) have enabled important advances in support of ITER and the physics basis of a spherical tokamak (ST) based component test facility (CTF), as well as providing new insight into underlying tokamak physics. For example, L-H transition studies benefit from high spatial and temporal resolution measurements of pedestal profile evolution (temperature, density and radial electric field) and in support of pedestal stability studies the edge current density profile has been inferred from motional Stark effect measurements. The influence of the q-profile and E × B flow shear on transport has been studied in MAST and equilibrium flow shear has been included in gyro-kinetic codes, improving comparisons with the experimental data. H-modes exhibit a weaker q and stronger collisionality dependence of heat diffusivity than implied by IPB98(y,2) scaling, which may have important implications for the design of an ST-based CTF. ELM mitigation, an important issue for ITER, has been demonstrated by applying resonant magnetic perturbations (RMPs) using both internal and external coils, but full stabilization of type-I ELMs has not been observed. Modelling shows the importance of including the plasma response to the RMP fields. MAST plasmas with q > 1 and weak central magnetic shear regularly exhibit a long-lived saturated ideal internal mode. Measured plasma braking in the presence of this mode compares well with neo-classical toroidal viscosity theory. In support of basic physics understanding, high resolution Thomson scattering measurements are providing new insight into sawtooth crash dynamics and neo-classical tearing mode critical island widths. Retarding field analyser measurements show elevated ion temperatures in the scrape-off layer of L-mode plasmas and, in the presence of type-I ELMs, ions with energy greater than 500 eV are detected 20 cm outside the separatrix. Disruption mitigation by massive gas injection has reduced divertor heat loads by up to 70%. © 2011 IAEA, Vienna.


Saturn: Storm-clouds brooding on towering heights

Nature 475 (2011) 44-45

P Read

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