Publications


Synchronization in a coupled two-layer quasigeostrophic model of baroclinic instability-Part 1: Master-slave configuration

Nonlinear Processes in Geophysics 16 (2009) 543-556

AA Castrejón-Pita, PL Read

Synchronization is studied using a pair of diffusively-coupled, two-layer quasi-geostrophic systems each comprising a single baroclinic wave and a zonal flow. In particular, the coupling between the systems is in the well-known master-slave or one-way configuration. Nonlinear time series analysis, phase dynamics, and bifurcation diagrams are used to study the dynamics of the coupled system. Phase synchronization, imperfect synchronization (phase slips), or complete synchronization are found, depending upon the strength of coupling, when the systems are either in a periodic or a chaotic regime. The results of investigations when the dynamics of each system are in different regimes are also presented. These results also show evidence of phase synchronization and signs of chaos control.


FLUID DYNAMICS Rotating convection on the edge

NATURE 457 (2009) 270-271

PL Read


The impact of methane thermodynamics on seasonal convection and circulation in a model Titan atmosphere

ICARUS 203 (2009) 250-264

JL Mitchell, RT Pierrehumbert, DMW Frierson, R Caballero


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


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


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

ANNALES GEOPHYSICAE 27 (2009) 3663-3676

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


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


Modeling Jupiter's cloud bands and decks. 1. Jet scale meridional circulations

Icarus 200 (2009) 548-562

LC Zuchowski, YH Yamazaki, PL Read

We have investigated the formation of jet scale meridional circulation cells on Jupiter in response to radiative and zonal momentum forcing. In the framework of semi-geostrophic theory, the meridional streamfunction is described by an elliptic equation with a source term dependent on the sum of the latitudinal derivative of the radiative forcing and the vertical derivative of the zonal momentum forcing. Using this equation with analytic terms similar to the assumed forcing on Jupiter, we obtained two set of atmospheric circulations cells, a stratospheric and a tropospheric one. A possible shift in the overturning circulation of the high and deep atmosphere can be induced by breaking the latitudinal alignment of radiative heating with the enforced belt and zones. A series of numerical simulations was conducted with the Jovian GCM OPUS, which was initiated with observational data obtained from the Cassini CIRS temperature cross-section and a corresponding geostrophic zonal wind field. Newtonian forcing of potential temperature as well as zonal momentum was applied respectively towards latitudinally and vertically uniform equilibrium fields. In accordance with the analytic illustrations two rows of jet scale circulation cells were created. The stratospheric circulation showed the distribution of upwelling over zones and downwelling over belts, consistent with cloud observations. The tropospheric cells featured a partial reversal of the downward vertical velocity over the belts and a considerable reduction of the upward movement over the zones in the domain, consistent with recent detections of high water clouds and lightning in belts. We also used the modeled new forcing fields as source terms for the semi-geostrophic Poisson equation to attribute the origin of the modeled secondary circulation. In this analysis, the stratospheric circulation cells observed in the model are primarily generated in response to radiative forcing, while momentum forcing induces the shifted configurations in the deep atmosphere. © 2008 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.


QUAGMIRE v1.3: a quasi-geostrophic model for investigating rotating fluids experiments

GEOSCIENTIFIC MODEL DEVELOPMENT 2 (2009) 13-32

PD Williams, TWN Haine, PL Read, SR Lewis, YH Yamazaki


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.


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

PHYSICS OF FLUIDS 20 (2008) ARTN 126602

RD Wordsworth, PL Read, YH Yamazaki


Testing the Trapped Gyro-Landau Fluid Transport Model with Data from Tokamaks and Spherical Tori

Proc. 22nd IAEA FEC (2008)

GM Staebler, G Colyer, S Kaye, JE Kinsey, RE Waltz


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.


Titan's winter polar vortex structure revealed by chemical tracers

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 113 (2008) ARTN E12003

NA Teanby, R de Kok, PGJ Irwin, S Osprey, S Vinatier, PJ Gierasch, PL Read, FM Flasar, BJ Conrath, RK Achterberg, B Bezard, CA Nixon, SB Calcutt


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

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