Publications


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.


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

GEOPHYSICAL RESEARCH LETTERS 34 (2007) ARTN L17812

H Brogniez, RT Pierrehumbert


An ocean of air: A natural history of the atmosphere

NATURE 447 (2007) 911-911

RT Pierrehumbert


Mapping potential-vorticity dynamics on Jupiter. II: The Great Red Spot from Voyager 1 and 2 data

Quarterly Journal of the Royal Meteorological Society 132 (2006) 1605-1625

PL Read, PJ Gierasch, BJ Conrath

Maps of Ertel potential vorticity on isentropic surfaces (IPV) and quasi-geostrophic potential vorticity (QGPV) on isobaric surfaces in the vicinity of Jupiter's Great Red Spot (GRS) are derived by making use of a combination of velocity measurements, derived from the tracking of cloud features in Voyager 1 and 2 images, and thermal measurements from the Voyager 1 IRIS instrument. The thermal data were obtained during Voyager 1's closest approach to Jupiter. IPV and QGPV in the vicinity of the GRS show a clearly isolated anticyclonic patch in the troposphere, with a suggestion of some spiral structure. The relationship of IPV and QGPV q with the corresponding isentropic or isobaric stream function Ψ near the GRS is not compatible with marginal stability with respect to Arnol'd's second stability theorem, and does not indicate a relaxed, maximum entropy structure except perhaps close to the tropopause. q(Ψ) in the upper troposphere and lower stratosphere for both Ertel and QGPV is reasonably well defined within the GRS and on a different branch to the ambient zonal flow, though is less well defined close to the cloud tops where local thermodynamic forcing may be significant. The profile in the upper troposphere is consistent with an isolated 'free mode' structure for which the air inside the GRS has a different dynamical origin to the atmosphere outside. © Royal Meteorological Society, 2006.


Reconstructing the weather on Mars at the time of the MERs and Beagle 2 landings

GEOPHYSICAL RESEARCH LETTERS 33 (2006) ARTN L19202

L Montabone, SR Lewis, PL Read, P Withers


The dynamics behind Titan's methane clouds.

Proceedings of the National Academy of Sciences of the United States of America 103 (2006) 18421-18426

JL Mitchell, RT Pierrehumbert, DMW Frierson, R Caballero

We present results of an axisymmetric global circulation model of Titan with a simplified suite of atmospheric physics forced by seasonally varying insolation. The recent discovery of midlatitude tropospheric clouds on Titan has caused much excitement about the roles of surface sources of methane and the global circulation in forming clouds. Although localized surface sources, such as methane geysers or "cryovolcanoes," have been invoked to explain these clouds, we find in this work that clouds appear in regions of convergence by the mean meridional circulation and over the poles during solstices, where the solar forcing reaches its seasonal maximum. Other regions are inhibited from forming clouds because of dynamical transports of methane and strong subsidence. We find that for a variety of moist regimes, i.e., with the effect of methane thermodynamics included, the observed cloud features can be explained by the large-scale dynamics of the atmosphere. Clouds at the solsticial pole are found to be a robust feature of Titan's dynamics, whereas isolated midlatitude clouds are present exclusively in a variety of moist dynamical regimes. In all cases, even without including methane thermodynamics, our model ceases to produce polar clouds approximately 4-6 terrestrial years after solstices.


Modelling the primary control of paleogeography on Cretaceous climate

EARTH AND PLANETARY SCIENCE LETTERS 248 (2006) 426-437

Y Donnadieu, R Pierrehumbert, R Jacob, F Fluteau


A GEOCLIM simulation of climatic and biogeochemical consequences of Pangea breakup

GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 7 (2006) ARTN Q11019

Y Donnadieu, Y Godderis, R Pierrehumbert, G Dromart, F Fluteau, R Jacob


Validation of martian meteorological data assimilation for MGS/TES using radio occultation measurements

ICARUS 185 (2006) 113-132

L Montabone, SR Lewis, PL Read, DP Hinson


Using microwave observations to assess large-scale control of free tropospheric water vapor in the mid-latitudes

GEOPHYSICAL RESEARCH LETTERS 33 (2006) ARTN L14801

H Brogniez, RT Pierrehumbert


Climate Change: A Catastrophe in Slow Motion

Chicago Journal of International Law 6 (2006) 6

RT Pierrehumbert


Direct numerical simulations of bifurcations in an air-filled rotating baroclinic annulus

JOURNAL OF FLUID MECHANICS 561 (2006) 359-389

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


Mapping potential vorticity dynamics on Jupiter: 1. zonal mean circulation from Cassini and Voyager 1 data

Quarterly Journal of the Royal Meteorological Society 132 (2006) 1577-1603

PL Read, P J Gierasch, B J Conrath, A Simon-Miller


Atmospheric temperature sounding on Mars, and the climate sounder on the 2005 reconnaissance orbiter

ADV SPACE RES 38 (2006) 713-717

FW Taylor, SB Calcutt, PL Read, SR Lewis, DJ McCleese, JT Schofield, RW Zurek

Detailed measurements of the vertical profiles of atmospheric temperature, water vapour, dust and condensates in the Martian atmosphere are needed to characterize the present-day Martian climate and to understand the intricately related processes upon which it depends. Among the most important of these are accurate and extensive temperature measurements. Progress to date, key problems still to be addressed and upcoming new approaches to the measurement task are briefly reviewed, and expectations for the Mars Climate Sounder experiment on the 2005 Mars Reconnaissance Orbiter are described. Some even more advanced methods for temperature, humidity and condensate sounding in the decade beyond MCS/MRO, and promising approaches to achieving these are also considered. (c) 2006 Published by Elsevier Ltd on behalf of COSPAR.


Instabilities of a barotropic shear layer in a rotating fluid: Asymmetries with respect to sgn(Ro)

Meteorologische Zeitschrift 15 (2006) 417-422

A Aguiar, P Read

The aim of the work reported in this article is to provide new insights into the dynamics and instabilities of a barotropic shear layer in a rotating fluid. Above a critical value of horizontal stress, the flow within a bounded system in rotation is driven to an unstable limit, beyond which it develops chains of vortices. The number of these vortices depends not only upon the value of the stress imposed but also on the sense of the shear in some cases, highlighting discrepancies between earlier experiments. Quasi-geostrophic theory, however, predicts that there should be no qualitative differences with respect to the sign of the stress. We present laboratory experiments in cylindrical geometry, where a detached shear layer occurs tangential to the differentially rotating sections at the top and bottom of the tank. For stepped end walls, we found that the spatial organization of the flow patterns is a function of the sign of Rossby number. Furthermore, we observe a weak dependence of the azimuthal wavenumber on the sign of Rossby number. © by Gebrüder Borntraeger 2006.


Synchronization and chaos control in a periodically forced quasi-geostrophic two-layer model of baroclinic instability

NONLINEAR PROCESSES IN GEOPHYSICS 13 (2006) 23-39

FJR Eccles, PL Read, TWN Haine


Mapping potential-vorticity dynamics on Jupiter. II: the Great Red Spot from Voyager 1 and 2 data

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 132 (2006) 1605-1625

PL Read, PJ Gierasch, BJ Conrath


Anisotropic turbulence and zonal jets in rotating flows with a beta-effect

NONLINEAR PROCESSES IN GEOPHYSICS 13 (2006) 83-98

B Galperin, S Sukoriansky, N Dikovskaya, PL Read, YH Yamazaki, R Wordsworth


Two scenarios on the driving mechanism of the Jovian equatorial jet with secondary hydrodynamic instabilities

ADV SPACE RES 38 (2006) 2639-2644

YH Yamazaki, PL Read

We test the feasibility of two scenarios that may drive the broad, prograde, equatorial jets in the Jovian atmosphere within the shallow "weather layer". The first idea attempts to explain the flat-headed jet as a consequence of a hydrodynamic instability along an equatorially trapped primarily jet. The strong primary jet is induced by a 300 in s(-1) Kelvin wave. The second idea is a bridging of a pair of off-equatorial jets due to horizontal eddy diffusion (the so-called Gierasch mechanism). The primary jets can be induced by a Hadley circulation, and might then be interconnected by subsequent hydrodynamic instabilities between them. We test the two scenarios using a general circulation model, but have so far been unable to obtain an equatorial jet that resembles observations. It appears, therefore, that the previously proposed model of combining Kelvin and Hadley forcing, is more plausible under the shallow hypothesis. (c) 2006 COSPAR. Published by Elsevier Ltd. All rights reserved.

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