Publications


Principles of Planetary Climate

Cambridge University Press, 2010

RT Pierrehumbert

This book introduces the reader to all the basic physical building blocks of climate needed to understand the present and past climate of Earth, the climates of Solar System planets, and the climates of extrasolar planets.


Predicting chaotic climates: from Earth to super-Earths?

MATHEMATICS AND ASTRONOMY: A JOINT LONG JOURNEY 1283 (2010) 57-74

PL Read


PyCCSM: Prototyping a python-based community climate system model

ANZIAM Journal 48 (2010) C1112-C1130

M Tobis, M Steder, J Walter Larson, RT Pierrehumbert, RL Jacob, ET Ong

© Austral. Mathematical Soc. 2010. Coupled climate models are multiphysics models comprising multi-ple separately developed codes that are combined into a single physical system. This composition of codes is amenable to a scripting solution, and Python is a language that offers many desirable properties for this task. We have prototyped a Python coupling and control infrastruc-ture for version 3.0 of the Community Climate System Model (ccsm3). Our objective was to improve dramatically ccsm3's already exible coupling facilities to enable research uses of the model not currently supported. We report the progress in the first steps in this effort: the construction of Python bindings for the Model Coupling Toolkit, a key piece of third-party coupling middleware used in ccsm3, and a Python-based ccsm3 coupler (pypcl) application. We report prelim-inary performance results for this new system, which we call pyccsm. We find pyccsm is significantly slower than its Fortran counterpart, and explain how pypcl's performance may be improved to support production runs. We believe our results augur well for the use of Python in the top-level coupling and organisation of large parallel multiphysics and multiscale applications.


Evidence for Climate Change on Mars

in Solar System Update, Springer (2010) 135-

SR Lewis, PL Read

This book, the first in a series of forthcoming volumes, consists of topical and timely reviews of a number of carefully selected topics in solar systemn science.


Element cycling and the evolution of the Earth System

GEOCHIMICA ET COSMOCHIMICA ACTA 74 (2010) A339-A339

Y Godderis, Y Donnadieu, JZ Williams, C Roelandt, J Schott, D Pollard, RT Pierrehumbert, S Brantley


Structure and dynamics of the Martian lower and middle atmosphere as observed by the Mars Climate Sounder: Seasonal variations in zonal mean temperature, dust, and water ice aerosols

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 115 (2010) ARTN E12016

DJ McCleese, NG Heavens, JT Schofield, WA Abdou, JL Bandfield, SB Calcutt, PGJ Irwin, DM Kass, A Kleinbohl, SR Lewis, DA Paige, PL Read, MI Richardson, JH Shirley, FW Taylor, N Teanby, RW Zurek


FLUID DYNAMICS Rotating convection on the edge

NATURE 457 (2009) 270-271

PL Read


Sensitivity of stable water isotopic values to convective parameterization schemes

GEOPHYSICAL RESEARCH LETTERS 36 (2009) ARTN L23801

J-E Lee, R Pierrehumbert, A Swann, BR Lintner


Synchronization of modulated traveling baroclinic waves in a periodically forced, rotating fluid annulus.

Phys Rev E Stat Nonlin Soft Matter Phys 79 (2009) 015202-

FJR Eccles, PL Read, AA Castrejón-Pita, TWN Haine

Frequency entrainment and nonlinear synchronization are commonly observed between simple oscillatory systems, but their occurrence and behavior in continuum fluid systems are much less well understood. Motivated by possible applications to geophysical fluid systems, such as in atmospheric circulation and climate dynamics, we have carried out an experimental study of the interaction of fully developed baroclinic instability in a differentially heated, rotating fluid annulus with an externally imposed periodic modulation of the thermal boundary conditions. In quasiperiodic and chaotic amplitude-modulated traveling wave regimes, the results demonstrate a strong interaction between the natural periodic modulation of the wave amplitude and the externally imposed forcing. This leads to partial or complete phase synchronization. Synchronization effects were observed even with very weak amplitudes of forcing, and were found with both 1:1 and 1:2 frequency ratios between forcing and natural oscillations.


Saturn's rotation period from its atmospheric planetary-wave configuration

NATURE 460 (2009) 608-610

PL Read, TE Dowling, G Schubert


Gyrokinetic simulations of spherical tokamaks

Plasma Physics and Controlled Fusion 51 (2009)

CM Roach, IG Abel, RJ Akers, W Arter, M Barnes, Y Camenen, FJ Casson, G Colyer, JW Connor, SC Cowley, D Dickinson, W Dorland, AR Field, W Guttenfelder, GW Hammett, RJ Hastie, E Highcock, NF Loureiro, AG Peeters, M Reshko, S Saarelma, AA Schekochihin, M Valovic, HR Wilson

This paper reviews transport and confinement in spherical tokamaks (STs) and our current physics understanding of this that is partly based on gyrokinetic simulations. Equilibrium flow shear plays an important role, and we show how this is consistently included in the gyrokinetic framework for flows that greatly exceed the diamagnetic velocity. The key geometry factors that influence the effectiveness of turbulence suppression by flow shear are discussed, and we show that toroidal equilibrium flow shear can sometimes entirely suppress ion scale turbulence in today's STs. Advanced nonlinear simulations of electron temperature gradient (ETG) driven turbulence, including kinetic ion physics, collisions and equilibrium flow shear, support the model that ETG turbulence can explain electron heat transport in many ST discharges. © 2009 IOP Publishing Ltd.


The snowball Earth aftermath: Exploring the limits of continental weathering processes

EARTH AND PLANETARY SCIENCE LETTERS 277 (2009) 453-463

G Le Hir, Y Donnadieu, Y Godderis, RT Pierrehumbert, GR Halverson, M Macouin, A Nedelec, G Ramstein


Mapping potential vorticity dynamics on saturn: Zonal mean circulation from Cassini and Voyager data

Planetary and Space Science 57 (2009) 1682-1698

PL Read, BJ Conrath, LN Fletcher, PJ Gierasch, AA Simon-Miller, LC Zuchowski

Maps of Ertel potential vorticity on isentropic surfaces (IPV) and quasi-geostrophic potential vorticity (QGPV) are well established in dynamical meteorology as powerful sources of insight into dynamical processes involving 'balanced' flow (i.e. geostrophic or similar). Here we derive maps of zonal mean IPV and QGPV in Saturn's upper troposphere and lower stratosphere by making use of a combination of velocity measurements, derived from the combined tracking of cloud features in images from the Voyager and Cassini missions, and thermal measurements from the Cassini Composite Infrared Spectrometer (CIRS) instrument. IPV and QGPV are mapped and compared for the entire globe between latitudes 89{ring operator} S - 82{ring operator} N. As on Jupiter, profiles of zonally averaged PV show evidence for a step-like "stair-case" pattern suggestive of local PV homogenisation, separated by strong PV gradients in association with eastward jets. The northward gradient of PV (IPV or QGPV) is found to change sign in several places in each hemisphere, however, even when baroclinic contributions are taken into account. The stability criterion with respect to Arnol'd's second stability theorem may be violated near the peaks of westward jets. Visible, near-IR and thermal-IR Cassini observations have shown that these regions exhibit many prominent, large-scale eddies and waves, e.g. including 'storm alley'. This suggests the possibility that at least some of these features originate from instabilities of the background zonal flow. © 2009 Elsevier Ltd.


Erratum to Kronos: Exploring the depths of Saturn with probes and remote sensing through an international mission

Experimental Astronomy 23 (2009) 977-980

B Marty, T Guillot, A Coustenis, N Achilleos, Y Alibert, S Asmar, D Atkinson, S Atreya, G Babasides, K Baines, T Balint, D Banfield, S Barber, B Bézard, GL Bjoraker, M Blanc, S Bolton, N Chanover, S Charnoz, E Chassefière, JE Colwell, E Deangelis, M Dougherty, P Drossart, FM Flasar, T Fouchet, R Frampton, I Franchi, D Gautier, L Gurvits, R Hueso, B Kazeminejad, T Krimigis, A Jambon, G Jones, Y Langevin, M Leese, E Lellouch, J Lunine, A Milillo, P Mahaffy, B Mauk, A Morse, M Moreira, X Moussas, C Murray, I Mueller-Wodarg, TC Owen, S Pogrebenko, R Prangé, P Read, A Sanchez-Lavega, P Sarda, D Stam, G Tinetti, P Zarka, J Zarnecki, J Schmidt, H Salo


Kronos: exploring the depths of Saturn with probes and remote sensing through an international mission

EXPERIMENTAL ASTRONOMY 23 (2009) 947-976

B Marty, T Guillot, A Coustenis, N Achilleos, Y Alibert, S Asmar, D Atkinson, S Atreya, G Babasides, K Baines, T Balint, D Banfield, S Barber, B Bezard, GL Bjoraker, M Blanc, S Bolton, N Chanover, S Charnoz, E Chassefiere, JE Colwell, E Deangelis, M Dougherty, P Drossart, FM Flasar, T Fouchet, R Frampton, I Franchi, D Gautier, L Gurvits, R Hueso, B Kazeminejad, T Krimigis, A Jambon, G Jones, Y Langevin, M Leese, E Lellouch, J Lunine, A Milillo, P Mahaffy, B Mauk, A Morse, M Moreira, X Moussas, C Murray, I Mueller-Wodarg, TC Owen, S Pogrebenko, R Prange, P Read, A Sanchez-Lavega, P Sarda, D Stam, G Tinetti, P Zarka, J Zarnecki, K Consortium


Low-order dynamical behavior in the martian atmosphere: Diagnosis of general circulation model results

Icarus 204 (2009) 48-62

O Martínez-Alvarado, IM Moroz, PL Read, SR Lewis, L Montabone

The hypothesis of a low dimensional martian climate attractor is investigated by the application of the proper orthogonal decomposition (POD) to a simulation of martian atmospheric circulation using the UK Mars general circulation model (UK-MGCM). In this article we focus on a time series of the interval between autumn and winter in the northern hemisphere, when baroclinic activity is intense. The POD is a statistical technique that allows the attribution of total energy (TE) to particular structures embedded in the UK-MGCM time-evolving circulation. These structures are called empirical orthogonal functions (EOFs). Ordering the EOFs according to their associated energy content, we were able to determine the necessary number to account for a chosen amount of atmospheric TE. We show that for Mars a large fraction of TE is explained by just a few EOFs (with 90% TE in 23 EOFs), which apparently support the initial hypothesis. We also show that the resulting EOFs represent classical types of atmospheric motion, such as thermal tides and transient waves. Thus, POD is shown to be an efficient method for the identification of different classes of atmospheric modes. It also provides insight into the non-linear interaction of these modes. © 2009 Elsevier Inc. All rights reserved.


Mars environment and magnetic orbiter model payload

EXPERIMENTAL ASTRONOMY 23 (2009) 761-783

B Langlais, F Leblanc, T Fouchet, S Barabash, D Breuer, E Chassefiere, A Coates, V Dehant, F Forget, H Lammer, S Lewis, M Lopez-Valverde, M Mandea, M Menvielle, A Pais, M Paetzold, P Read, C Sotin, P Tarits, S Vennerstrom, G Branduardi-Raymont, G Cremonese, JGM Merayo, T Ott, H Reme, JG Trotignon, JE Walhund


Mars environment and magnetic orbiter scientific and measurement objectives.

Astrobiology 9 (2009) 71-89

F Leblanc, B Langlais, T Fouchet, S Barabash, D Breuer, E Chassefière, A Coates, V Dehant, F Forget, H Lammer, S Lewis, M Lopez-Valverde, M Mandea, M Menvielle, A Pais, M Paetzold, P Read, C Sotin, P Tarits, S Vennerstrom

In this paper, we summarize our present understanding of Mars' atmosphere, magnetic field, and surface and address past evolution of these features. Key scientific questions concerning Mars' surface, atmosphere, and magnetic field, along with the planet's interaction with solar wind, are discussed. We also define what key parameters and measurements should be performed and the main characteristics of a martian mission that would help to provide answers to these questions. Such a mission--Mars Environment and Magnetic Orbiter (MEMO)--was proposed as an answer to the Cosmic Vision Call of Opportunity as an M-class mission (corresponding to a total European Space Agency cost of less than 300 Meuro). MEMO was designed to study the strong interconnection between the planetary interior, atmosphere, and solar conditions, which is essential to our understanding of planetary evolution, the appearance of life, and its sustainability. The MEMO main platform combined remote sensing and in situ measurements of the atmosphere and the magnetic field during regular incursions into the martian upper atmosphere. The micro-satellite was designed to perform simultaneous in situ solar wind measurements. MEMO was defined to conduct: * Four-dimensional mapping of the martian atmosphere from the surface up to 120 km by measuring wind, temperature, water, and composition, all of which would provide a complete view of the martian climate and photochemical system; Mapping of the low-altitude magnetic field with unprecedented geographical, altitude, local time, and seasonal resolutions; A characterization of the simultaneous responses of the atmosphere, magnetic field, and near-Mars space to solar variability by means of in situ atmospheric and solar wind measurements.


Transient teleconnection event at the onset of a planet-encircling dust storm on Mars

Annales Geophysicae 27 (2009) 3663-3676

O Martínez-Alvarado, L Montabone, SR Lewis, IM Moroz, PL Read

We use proper orthogonal decomposition (POD) to study a transient teleconnection event at the onset of the 2001 planet-encircling dust storm on Mars, in terms of empirical orthogonal functions (EOFs). There are several differences between this and previous studies of atmospheric events using EOFs. First, instead of using a single variable such as surface pressure or geopotential height on a given pressure surface, we use a dataset describing the evolution in time of global and fully three-dimensional atmospheric fields such as horizontal velocity and temperature. These fields are produced by assimilating Thermal Emission Spectrometer observations from NASA's Mars Global Surveyor spacecraft into a Mars general circulation model. We use total atmospheric energy (TE) as a physically meaningful quantity which weights the state variables. Second, instead of adopting the EOFs to define teleconnection patterns as planetary-scale correlations that explain a large portion of long time-scale variability, we use EOFs to understand transient processes due to localised heating perturbations that have implications for the atmospheric circulation over distant regions. The localised perturbation is given by anomalous heating due to the enhanced presence of dust around the northern edge of the Hellas Planitia basin on Mars. We show that the localised disturbance is seemingly restricted to a small number (a few tens) of EOFs. These can be classified as low-order, transitional, or high-order EOFs according to the TE amount they explain throughout the event. Despite the global character of the EOFs, they show the capability of accounting for the localised effects of the perturbation via the presence of specific centres of action. We finally discuss possible applications for the study of terrestrial phenomena with similar characteristics.


Modeling Jupiter's cloud bands and decks. 2. Distribution and motion of condensates

Icarus 200 (2009) 563-573

LC Zuchowski, YH Yamazaki, PL Read

A simple jovian cloud scheme has been developed for the Oxford Planetary Unified model System (OPUS). NH3-ice, NH4SH-solid, H2O-ice and H2O-liquid clouds have been modeled in Southern hemisphere limited area simulations of Jupiter. We found that either three or four of the condensates existed in the model. For a deep atmospheric water abundance close to solar composition, an NH3-ice deck above 0.7 bar, an NH4SH-solid deck above 2.5 bar and a H2O-liquid deck with a base at about 7.5 bar and frozen cloud tops formed. If a depleted deep water abundance is assumed, however, a very compact cloud structure develops, where an H2O-ice cloud forms by direct sublimation above 3 bar. The condensates constitute good tracers of atmospheric motion, and we have confirmed that zonal velocities determined from manual feature tracking in the modeled cloud layers agree reasonably well with the modeled zonal velocities. Dense and elevated clouds form over latitudes with strong atmospheric upwelling and depleted clouds exist over areas with strong downwelling. In the NH3-ice deck this leads to elevated cloud bands over the zones in the domain and thin clouds over the belts, which is consistent with the observationally deduced distribution. Due to changes in the vertical velocity pattern in the deeper atmosphere, the NH4SH-solid and water cloud decks are more uniform. This modeled cloud structure thus includes the possibility of more frequent water cloud observations in belts, as this deeper deck could be more easily detected under areas with thin NH3-ice clouds. Large scale vortices appeared spontaneously in the model and were characterized by elevated NH3-ice clouds, as expected from observations. These eddies leave the most discernible imprint on the lighter condensate particles of the uppermost layer. © 2008 Elsevier Inc. All rights reserved.

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