Publications


Laboratory and numerical studies of baroclinic waves in an internally heated rotating fluid annulus: A case of wave/vortex duality?

JOURNAL OF FLUID MECHANICS 337 (1997) 155-191

PL Read, SR Lewis, R Hide


Wave interactions and the transition to chaos of baroclinic waves in a thermally driven rotating annulus

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 355 (1997) 101-153

WG Fruh, PL Read


Data assimilation with a Martian atmospheric GCM: An example using thermal data

ADV SPACE RES 19 (1997) 1267-1270

SR Lewis, M Collins, PL Read

Data assimilation is a technique for the analysis of atmospheric observations which combines current information with prior knowledge from previous observations, summarized and forecast in time via the use of a numerical model. A sequential data assimilation scheme has been implemented with a full general circulation model (GCM) of the martian atmosphere for the first time, and has been adapted for the types of atmospheric data which might be expected in the near future, e.g. remote-sensed temperature profiles from a polar orbiter mission such as Mars Surveyor '96 and '98. Tests demonstrate the performance of the scheme using artificial data generated from independent model experiments. (C) 1997 COSPAR. Published by Elsevier Science Ltd.


Lower-tropospheric heat transport in the Pacific storm track

JOURNAL OF THE ATMOSPHERIC SCIENCES 54 (1997) 1533-1543

KL Swanson, RT Pierrehumbert


Baroclinic wave transitions in the Martian atmosphere

ICARUS 120 (1996) 344-357

M Collins, SR Lewis, PL Read, F Hourdin


Martian atmospheric data assimilation with a simplified general circulation model: Orbiter and lander networks

Planetary and Space Science 44 (1996) 1395-1409

SR Lewis, PL Read, M Collins

A meteorological data assimilation scheme for the martian atmosphere has been implemented and tested, based on techniques used in the current operational scheme for weather forecasting at the U.K. Meteorological Office. The scheme has been interfaced with a range of simple models and with the martian GCM currently under simultaneous development at Laboratoire de Météorologie Dynamique du CNRS in Paris and at Oxford. As well as the interpretation of data from any future spacecraft, the assimilation scheme may be used for comparisons between different models, for model validation using earlier martian data, and for data impact studies to assist in planning new missions. Despite proposed new missions to Mars, observations of the atmosphere of Mars in the near future are still likely to be very sparse compared to those of the Earth (perhaps comprising a single orbiter and a few surface stations at any one time) and the scheme has been adapted with this in mind. Twin model experiments are conducted in which simulated observations are generated from a second model started from different initial conditions. Such experiments reveal the importance of surface pressure measurements (in combination with an accurate topographic map, such as will be available from laser altimetry) in the determination of the amplitude of large-scale atmospheric waves. It is shown that atmospheric temperature profiles from a remote-sensing instrument on a polar orbiting satellite combined with simultaneous surface pressure observations at a limited number of sites, as planned for the InterMarsNet mission, is a useful scenario for data assimilation. Copyright © 1996 Elsevier Science Ltd.


Anomalous scaling of high cloud variability in the tropical Pacific

GEOPHYSICAL RESEARCH LETTERS 23 (1996) 1095-1098

RT Pierrehumbert


Martian atmospheric data assimilation with a simplified general circulation model: Orbiter and lander networks

PLANET SPACE SCI 44 (1996) 1395-1409

SR Lewis, PL Read, M Collins

A meteorological data assimilation scheme for the martian atmosphere has been implemented and tested, based on techniques used in the current operational scheme for weather forecasting at the U.K. Meteorological Office. The scheme has been interfaced with a range of simple models and with the martian GCM currently under simultaneous development at Laboratoire de Meteorologie Dynamique du CNRS in Paris and at Oxford. As well as the interpretation of data from any future spacecraft, the assimilation scheme may be used for comparisons between different models, for model validation using earlier martian data, and for data impact studies to assist in planning new missions. Despite proposed new missions to Mars, observations of the atmosphere of Mars in the near future are still likely to be very sparse compared to those of the Earth (perhaps comprising a single orbiter and a few surface stations at any one time) and the scheme has been adapted with this in mind. Twin model experiments are conducted in which simulated observations are generated from a second model started from different initial conditions. Such experiments reveal the importance of surface pressure measurements (in combination with an accurate topographic map, such as will be available from laser altimetry) in the determination of the amplitude of large-scale atmospheric waves. It is shown that atmospheric temperature profiles from a remote-sensing instrument on a polar orbiting satellite combined with simultaneous surface pressure observations at a limited number of sites, as planned for the InterMarsNet mission, is a useful scenario for data assimilation. Copyright (C) 1996 Elsevier Science Ltd


Numerical modelling of the general circulation of the Martian atmosphere

European Space Agency, (Special Publication) ESA SP (1996) 315-320

F Hourdin, F Forget, R Fournier, O Talagrand, PL Read, M Collins, SR Lewis, NPJ Thomas, JP Huot

General Circulation Models, originally developed for the needs of terrestrial meteorology and climatology, have become in the last twenty years a central tool of Martian climate studies. This paper descrcibes how numerical simulation can be also used for determining the environment for a probe. It also highlights the recent modellig efforts which have been made jointly at LMD/CNRS (Paris) and AOPP (Oxford) to develop a new-generation General Circulation Model in order to produce a Martian climate database for the European Space Agency.


A climate database for the Martian atmosphere

European Space Agency, (Special Publication) ESA SP (1996) 323-327

M Collins, SR Lewis, PL Read, NPJ Thomas, O Talagrand, F Forget, R Fournier, F Hourdin, JP Huot

A new engineering model of the environment of Mars is outlined. The model is based on a database of statistics computed from a state-of-the-art Global Circulation Model of the martian atmosphere which represents our best knowledge of the atmosphere to date. A novel scheme for the representation of large scale variability in the engineering model, in terms of an optimal set of basis functions derived from the Global Circulation Model, is also outlined and shown to be an efficient and accurate method of representing correlated structures in vertical profiles.


Baroclinic instability

(1995)

RT Pierrehumbert, KL Swanson

The study of baroclinic instability has its origins in attempts to explain the genesis of midlatitude synoptic storm systems. The authors provide an account of the fundamental material and unfamiliar aspects of the linear theory. Essential observational background is provided in section 2, and the mathematical basics are laid out in section 3. The review for the most part focuses on quasigeostrophic dynamics, considering only dry dynamics. Discussion is slanted towards the terrestrial atmosphere. Stability criteria are treated in section 4, and normal modes are discussed in section 5. Aspects of the linear initial value problem are taken up in section 6. Section 7 considers briefly the difficult subject of nonlinear equilibration. Finally, section 8, takes stock of where the subject stands and where it is going. (from Authors)


Regular and irregular baroclinic waves in a Martian general circulation model: A role for diurnal forcing?

ADV SPACE RES 16 (1995) 3-7

M COLLINS, SR LEWIS, PL READ

The development and evolution of baroclinic transient waves are simulated in a high resolution, general circulation model (GCM) of the Martian atmosphere, including simulations both with and without a representation of the diurnal cycle of solar heating. Simulations with diurnally-averaged insolation are found to develop highly regular baroclinic transients during northern hemisphere autumn, winter and spring seasons, characterized by zonal wavenumber 1 or 2 and periods of 2-6 sols (a sol being a Martian day). With a diurnal cycle, however, transients are found to be significantly more irregular throughout the winter season, sporadically changing their dominant wavenumber and frequency, and resemble more closely data from the Viking Lander time series. These results are discussed with reference to some simple conceptual models in nonlinear dynamics, in terms either of a periodically-perturbed, self-exciting oscillator, or of attractor-merging near a crisis in a periodically perturbed bistable system.


Baroclinic instability

(1995)

RT Pierrehumbert, KL Swanson

The study of baroclinic instability has its origins in attempts to explain the genesis of midlatitude synoptic storm systems. The authors provide an account of the fundamental material and unfamiliar aspects of the linear theory. Essential observational background is provided in section 2, and the mathematical basics are laid out in section 3. The review for the most part focuses on quasigeostrophic dynamics, considering only dry dynamics. Discussion is slanted towards the terrestrial atmosphere. Stability criteria are treated in section 4, and normal modes are discussed in section 5. Aspects of the linear initial value problem are taken up in section 6. Section 7 considers briefly the difficult subject of nonlinear equilibration. Finally, section 8, takes stock of where the subject stands and where it is going. (from Authors)


An operational data assimilation scheme for the Martian atmosphere

ADV SPACE RES 16 (1995) 9-13

SR LEWIS, PL READ

A meteorological data assimilation scheme has been developed for Mars, based on techniques used for the current operational scheme at the UK Meteorological Office (UKMO). The scheme has been designed to interface with a range of models of varying complexity, from a simple primitive equations model to a full martian general circulation model with detailed parameterizations of the most important physical processes. The scheme was originally intended to be used primarily for analysis of temperature profiles from the Pressure Modulator Infrared Radiometer (PMIRR) onboard the Mars Observer (MO) spacecraft. It is, however, capable of analysing any asynoptic, randomly-distributed dataset, which may include surface pressure, temperature, velocity or constituent data originating either from other past or future spacecraft missions or from models. It is proposed to use the scheme not only for interpretation of forthcoming data from future spacecraft but also for model inter-comparisons, for hind-casting earlier martian data for model validation and for data impact studies in the planning of new missions. Initial results have demonstrated successful assimilations of trial orbiter and lander data into models with different initial conditions and physics, although a large number of landers might be required if orbiter data were not available. An optimum approach would combine orbiter data with simultaneous measurements from a small number of landers.


SURFACE QUASI-GEOSTROPHIC DYNAMICS

JOURNAL OF FLUID MECHANICS 282 (1995) 1-20

IM HELD, RT PIERREHUMBERT, ST GARNER, KL SWANSON


THERMOSTATS, RADIATOR FINS, AND THE LOCAL RUNAWAY GREENHOUSE

JOURNAL OF THE ATMOSPHERIC SCIENCES 52 (1995) 1784-1806

RT PIERREHUMBERT


POTENTIAL VORTICITY HOMOGENIZATION AND STATIONARY WAVES

JOURNAL OF THE ATMOSPHERIC SCIENCES 52 (1995) 990-994

KL SWANSON, RT PIERREHUMBERT


The mixing paradigm: Towards a Lagrangian view of the general circulation

ENVIRONMENT AND QUALITY OF LIFE (1995) 102-113

RT PIERREHUMBERT


Temperature fluctuations and atmospheric heat flux

TENTH CONFERENCE ON ATMOSPHERIC AND OCEANIC WAVES AND STABILITY (1995) 196-197

KL Swanson, RT Pierrehumbert, AM SOC


WESTERN BOUNDARY CURRENTS IN THE MARTIAN ATMOSPHERE - NUMERICAL SIMULATIONS AND OBSERVATIONAL EVIDENCE

JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS 100 (1995) 5485-5500

MM JOSHI, SR LEWIS, PL READ, DC CATLING

Pages