Ertel potential vorticity versus Bernoulli streamfunction on Mars

Quarterly Journal of the Royal Meteorological Society Wiley 143 (2016) 37-52

TE Dowling, ME Bradley, J Du, SR Lewis, P Read

Scatter plots of Ertel potential vorticity, Q, versus Bernoulli streamfunction, B, on potential temperature surfaces, θ, are investigated for Mars using the global Mars Analysis Correction Data Assimilation (MACDA) reanalysis, which spans Mars Year (MY) 24.39 to 27.24. In midlatitudes, Mars exhibits monotonic, function-like Q(B) correlations on θ surfaces similar to those observed for Earth. We quantify this with linear regressions of Q versus B over the vertical range θ=400 to 900 K (∼30 to 60 km). In autumn, winter and spring, in both hemispheres, the non-dimensionalized correlation generally lies between zero and unity and gradually decreases with height, whereas in northern summer, it swings negative. These characteristics match Earth's lower mesosphere (θ= 2000 to 3000 K; z≈ 48 to 62 km) during the same seasons. The exception is southern summer, when the correlation on Mars nearly vanishes. In time series, the transition into and out of northern summer is sinuous and centred just after solar longitude Ls = 90°, whereas in southern summer it is abrupt and spans ΔLs≈120°, which is one third of a Mars year. A striking feature seen on Mars but not on Earth is a large range of Q over the narrow domain of B poleward of each winter polar jet, particularly in the north, which is consistent with the known annular structure of the Martian polar vortex. Froude number calculations suggest the existence of a planetary-scale hydraulic jump associated with the winter polar jet.

Observational evidence against strongly stabilizing tropical cloud feedbacks

Geophysical Research Letters American Geophysical Union 44 (2017) 1503-1510

IN Williams, R Pierrehumbert

We present a method to attribute cloud radiative feedbacks to convective processes, using sub-cloud layer buoyancy as a diagnostic of stable and deep convective regimes. Applying this approach to tropical remote-sensing measurements over years 2000-2016 shows that an inferred negative short-term cloud feedback from deep convection was nearly offset by a positive cloud feedback from stable regimes. The net cloud feedback was within statistical uncertainty of the NCAR Community Atmosphere Model (CAM5) with historical forcings, with discrepancies in the partitioning of the cloud feedback into convective regimes. Compensation between high-cloud responses to tropics-wide warming in stable and unstable regimes resulted in smaller net changes in high-cloud fraction with warming. In addition, deep convection and associated high clouds set in at warmer temperatures in response to warming, as a consequence of nearly invariant sub-cloud buoyancy. This invariance further constrained the magnitude of cloud radiative feedbacks, and is consistent with climate model projections.

Linking the climate and thermal phase curve of 55 Cancri e

Astrophysical Journal American Astronomical Society (2017)

M Hammond, R Pierrehumbert

The thermal phase curve of 55 Cancri e is the first measurement of the temperature distribution of a tidally locked Super-Earth, but raises a number of puzzling questions about the planet's climate. The phase curve has a high amplitude and peak offset, suggesting that it has a significant eastward hot-spot shift as well as a large day-night temperature contrast. We use a general circulation model to model potential climates, and investigate the relation between bulk atmospheric composition and the magnitude of these seemingly contradictory features. We confirm theoretical models of tidally locked circulation are consistent with our numerical model of 55 Cnc e, and rule out certain atmospheric compositions based on their thermodynamic properties. Our best-fitting atmosphere has a significant hot- spot shift and day-night contrast, although these are not as large as the observed phase curve. We discuss possible physical processes which could explain the observations, and show that night-side cloud formation from species such as SiO from a day-side magma ocean could potentially increase the phase curve amplitude and explain the observations. We conclude that the observations could be explained by an optically thick atmosphere with a low mean molecular weight, a surface pressure of several bar and a strong eastward circulation, with night-side cloud formation a possible explanation for the difference between our model and the observations.

Collisionality scaling of the electron heat flux in ETG turbulence

Plasma Physics and Controlled Fusion IOP Publishing 59 (2017) 1-25

GJ Colyer, AA Schekochihin, FI Parra, CM Roach, MA Barnes, Y-C Ghim, W Dorland

In electrostatic simulations of MAST plasma at electron-gyroradius scales, using the local flux-tube gyrokinetic code GS2 with adiabatic ions, we find that the long-time saturated electron heat flux (the level most relevant to energy transport) decreases as the electron collisionality decreases. At early simulation times, the heat flux "quasi-saturates" without any strong dependence on collisionality, and with the turbulence dominated by streamer-like radially elongated structures. However, the zonal fluctuation component continues to grow slowly until much later times, eventually leading to a new saturated state dominated by zonal modes and with the heat flux proportional to the collision rate, in approximate agreement with the experimentally observed collisionality scaling of the energy confinement in MAST. We outline an explanation of this effect based on a model of ETG turbulence dominated by zonal-nonzonal interactions and on an analytically derived scaling of the zonal-mode damping rate with the electron-ion collisionality. Improved energy confinement with decreasing collisionality is favourable towards the performance of future, hotter devices.

Synchronisation of the equatorial QBO by the annual cycle in tropical upwelling in a warming climate

Quarterly Journal of the Royal Meteorological Society John Wiley and Sons Ltd 142 (2016) 1111–1120-

K Rajendran, IM Moroz, PL Read, S Osprey

<p>The response of the period of the quasi-biennial oscillation (QBO) to increases in tropical upwelling are considered using a one-dimensional model. We find that the imposition of the annual cycle in tropical upwelling creates substantial variability in the period of the QBO. The annual cycle creates synchronisation regions in the wave forcing space, within which the QBO period locks onto an integer multiple of the annual forcing period. Outside of these regions, the QBO period undergoes discrete jumps as it attempts to find a stable relationship with the oscillator forcing. The resulting set of QBO periods can be either discrete or broad-banded, depending on the intrinsic period of the QBO.</p> <p>We use the same model to study the evolution of the QBO period as the strength of tropical upwelling increases as would be expected in a warmer climate. The QBO period lengthens and migrates closer towards 36 and 48 month locking regions as upwelling increases. The QBO period does not vary continuously with increased upwelling, however, but instead transitions through a series of 2- and 3-cycles before becoming locked to the annual cycle. Finally, some observational evidence for the cyclical behaviour of the QBO periods in the real atmosphere is presented.</p>

Global energy budgets and 'Trenberth diagrams' for the climates of terrestrial and gas giant planets

Quarterly Journal of the Royal Meteorological Society Wiley 142 (2016) 703–720-

PL Read, J Barstow, B Charnay, S Chelvaniththilan, PGJ Irwin, S Knight, S Lebonnois, SR Lewis, J Mendonça, L Montabone

The climate on Earth is generally determined by the amount and distribution of incoming solar radiation, which must be balanced in equilibrium by the emission of thermal radiation from the surface and atmosphere. The precise routes by which incoming energy is transferred from the surface and within the atmosphere and back out to space, however, are important features that characterize the current climate. This has been analysed in the past by several groups over the years,based on combinations of numerical model simulations and direct observations of theEarths climate system. The results are often presented in schematic form to show the main routes for the transfer of energy into, out of and within the climate system. Although relatively simple in concept, such diagrams convey a great deal of information about the climate system in a compact form. Such an approach has not so far been widely adopted in any systematic way for other planets of the Solar System, let alone beyond, although quite detailed climate models of several planets are now available, constrained bymany new observations and measurements. Here we present an analysis of the global transfers of energy within the climate systems of a range of planets within the Solar System,including Mars, Titan, Venus a nd Jupit er, a s mo delled by rela t ively co mprehens iveradiative transfer and (in some cases) numerical circulation models. These results are presented in schematic form for comparison with the classical global energy budget analyses (e.g.Trenberth et al. 2009; Stephenset al.2012; Wildet al.2013; IPCC 2013)for the Earth, highlighting important similarities and differences. We also take the first steps towards extending this approach to other Solar System and extra-solar planets,including Mars, Venus, Titan, Jupiter and the ‘hot Jupiter’ exoplanet HD189733b, presenting a synthesis of `both previously published and new calculations for all of these planets.

5 Things We Know to Be True.

Scientific American 315 (2016) 46-53

M Shermer, H Hall, R Pierrehumbert, P Offit, S Shostak

Consequences of twenty-first-century policy for multi-millennial climate and sea-level change

NATURE CLIMATE CHANGE 6 (2016) 360-369

PU Clark, JD Shakun, SA Marcott, AC Mix, M Eby, S Kulp, A Levermann, GA Milne, PL Pfister, BD Santer, DP Schrag, S Solomon, TF Stocker, BH Strauss, AJ Weaver, R Winkelmann, D Archer, E Bard, A Goldner, K Lambeck, RT Pierrehumbert, G-K Plattner

A regime diagram for ocean geostrophic turbulence

Quarterly Journal of the Royal Meteorological Society Wiley 142 (2016) 2411–2417-

DP Marshall, A Klocker, SR Keating, PL Read

A two-dimensional regime diagram for geostrophic turbulence in the ocean is constructed by plotting observation-based estimates of the nondimensional eddy radius and unsuppressed mixing length against a nonlinearity parameter equal to the ratio of the root-mean square eddy velocity and baroclinic Rossby phase speed. For weak nonlinearity, as found in the tropics, the mixing length mostly corresponds to the stability threshold for baroclinic instability whereas the eddy radius corresponds to the Rhines scale; it is suggested that this mismatch is indicative of the inverse energy cascade that occurs at low latitudes in the ocean and the zonal elongation of eddies. At larger values of nonlinearity, as found at mid- and high-latitudes, the eddy length scales are much shorter than the stability threshold, within a factor of 2.5 of the Rossby deformation radius.

How to decarbonize? Look to Sweden

Bulletin of the Atomic Scientists Routledge 72 (2016) 105-111

R Pierrehumbert

Bringing global warming to a halt requires that worldwide net emissions of carbon dioxide be brought to essentially zero, and the sooner this occurs, the less warming our descendants for the next thousand years and more will need to adapt to. The widespread fear that the actions needed to bring this about conflict with economic growth is a major impediment to efforts to protect the climate. However, much of this fear is pointless, and the magnitude of the task, while great, is no greater than challenges human ingenuity has surmounted in the past. To light the way forward, there is a need for examining success stories in which nations have greatly reduced their carbon dioxide emissions while simultaneously maintaining vigorous growth in the standard of living. In this article, the example of Sweden is showcased. Through a combination of sensible government infrastructure policies and free-market incentives, Sweden has managed to successfully decarbonize, cutting its per capita emissions by a factor of three since the 1970s, while doubling its pre capita income and providing a wide range of social benefits. This has all be accomplished within a vigorous capitalistic framework which in many ways embodies freemarket principles better than the economy of the United States.

Convection in condensible-rich atmospheres

Astrophysical Journal IOP Publishing 822 (2016) 24-24

F Ding, R Pierrehumbert

Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth's present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO2 is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

The effects of short-lived radionuclides and porosity on the early thermo-mechanical evolution of planetesimals

Icarus Elsevier BV 274 (2016) 350-365

T Lichtenberg, GJ Golabek, TV Gerya, MR Meyer

Isotopic enrichment of forming planetary systems from supernova pollution

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 462 (2016) 3979-3992

T Lichtenberg, RJ Parker, MR Meyer

Dynamics of atmospheres with a non-dilute condensible component

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences Royal Society 472 (2016) 20160107

R Pierrehumbert, F Ding

The diversity of characteristics for the host of recently discovered exoplanets opens up a great deal of fertile new territory for geophysical fluid dynamics, particularly when the fluid flow is coupled to novel thermodynamics, radiative transfer or chemistry. In this paper, we survey one of these new areas—the climate dynamics of atmospheres with a non-dilute condensible component, defined as the situation in which a condensible component of the atmosphere makes up a substantial fraction of the atmospheric mass within some layer. Non-dilute dynamics can occur for a wide range of condensibles, generically applying near both the inner and the outer edges of the conventional habitable zone and in connection with runaway greenhouse phenomena. It also applies in a wide variety of other planetary circumstances. We first present a number of analytical results developing some key features of non-dilute atmospheres, and then show how some of these features are manifest in simulations with a general circulation model adapted to handle non-dilute atmospheres. We find that non-dilute atmospheres have weak horizontal temperature gradients even for rapidly rotating planets, and that their circulations are largely barotropic. The relative humidity of the condensible component tends towards 100% as the atmosphere becomes more non-dilute, which has important implications for runaway greenhouse thresholds. Non-dilute atmospheres exhibit a number of interesting organized convection features, for which there is not yet any adequate theoretical understanding.

New use of global warming potentials to compare cumulative and short-lived climate pollutants

Nature Climate Change Nature Publishing Group (2016)

A Reisinger, R Pierrehumbert, MR Allen, JS Fuglestvedt, KP Shine, PM Forster

Parties to the United Nations Framework Convention on Climate Change (UNFCCC) have requested guidance on common greenhouse gas metrics in accounting for Nationally determined contributions (NDCs) to emission reductions1. Metric choice can affect the relative emphasis placed on reductions of ‘cumulative climate pollutants’ such as carbon dioxide versus ‘short-lived climate pollutants’ (SLCPs), including methane and black carbon2, 3, 4, 5, 6. Here we show that the widely used 100-year global warming potential (GWP100) effectively measures the relative impact of both cumulative pollutants and SLCPs on realized warming 20–40 years after the time of emission. If the overall goal of climate policy is to limit peak warming, GWP100 therefore overstates the importance of current SLCP emissions unless stringent and immediate reductions of all climate pollutants result in temperatures nearing their peak soon after mid-century7, 8, 9, 10, which may be necessary to limit warming to “well below 2 °C” (ref. 1). The GWP100 can be used to approximately equate a one-off pulse emission of a cumulative pollutant and an indefinitely sustained change in the rate of emission of an SLCP11, 12, 13. The climate implications of traditional CO2-equivalent targets are ambiguous unless contributions from cumulative pollutants and SLCPs are specified separately.

Exploring the Venus global super-rotation using a comprehensive general circulation model

Planetary and Space Science Elsevier 134 (2016) 1-18

JM Mendonça, P Read

The atmospheric circulation in Venus is well known to exhibit strong super-rotation. However, the atmospheric mechanisms responsible for the formation of this super-rotation are still not fully understood. In this work, we developed a new Venus general circulation model to study the most likely mechanisms driving the atmosphere to the current observed circulation. Our model includes a new radiative transfer, convection and suitably adapted boundary layer schemes and a dynamical core that takes into account the dependence of the heat capacity at constant pressure with temperature.The new Venus model is able to simulate a super-rotation phenomenon in the cloud region quantitatively similar to the one observed. The mechanisms maintaining the strong winds in the cloud region were found in the model results to be a combination of zonal mean circulation, thermal tides and transient waves. In this process, the semi-diurnal tide excited in the upper clouds has a key contribution in transporting axial angular momentum mainly from the upper atmosphere towards the cloud region. The magnitude of the super-rotation in the cloud region is sensitive to various radiative parameters such as the amount of solar radiative energy absorbed by the surface, which controls the static stability near the surface. In this work, we also discuss the main difficulties in representing the flow below the cloud base in Venus atmospheric models.Our new radiative scheme is more suitable for 3D Venus climate models than those used in previous work due to its easy adaptability to different atmospheric conditions. This flexibility of the model was crucial to explore the uncertainties in the lower atmospheric conditions and may also be used in the future to explore, for example, dynamical-radiative-microphysical feedbacks.

The solsticial pause on Mars: 1. A planetary wave reanalysis

ICARUS Elsevier 264 (2016) 456-464

SR Lewis, DP Mulholland, P Read, L Montabone, RJ Wilson, MD Smith

Large-scale planetary waves are diagnosed from an analysis of profiles retrieved from the Thermal Emission Spectrometer aboard the Mars Global Surveyor spacecraft during its scientific mapping phase. The analysis is conducted by assimilating thermal profiles and total dust opacity retrievals into a Mars global circulation model. Transient waves are largest throughout the northern hemisphere autumn, winter and spring period and almost absent during the summer. The southern hemisphere exhibits generally weaker transient wave behaviour. A striking feature of the low-altitude transient waves in the analysis is that they show a broad subsidiary minimum in amplitude centred on the winter solstice, a period when the thermal contrast between the summer hemisphere and the winter pole is strongest and baroclinic wave activity might be expected to be strong. This behaviour, here called the 'solsticial pause,' is present in every year of the analysis. This strong pause is under-represented in many independent model experiments, which tend to produce relatively uniform baroclinic wave activity throughout the winter. This paper documents and diagnoses the transient wave solsticial pause found in the analysis; a companion paper investigates the origin of the phenomenon in a series of model experiments.

The physics of Martian weather and climate: a review.

Reports on progress in physics. Physical Society (Great Britain) IOP Publishing 78 (2015) 125901-

P Read, SR Lewis, DP Mulholland

The planet Mars hosts an atmosphere that is perhaps the closest in terms of its meteorology and climate to that of the Earth. But Mars differs from Earth in its greater distance from the Sun, its smaller size, its lack of liquid oceans and its thinner atmosphere, composed mainly of CO2. These factors give Mars a rather different climate to that of the Earth. In this article we review various aspects of the martian climate system from a physicist's viewpoint, focusing on the processes that control the martian environment and comparing these with corresponding processes on Earth. These include the radiative and thermodynamical processes that determine the surface temperature and vertical structure of the atmosphere, the fluid dynamics of its atmospheric motions, and the key cycles of mineral dust and volatile transport. In many ways, the climate of Mars is as complicated and diverse as that of the Earth, with complex nonlinear feedbacks that affect its response to variations in external forcing. Recent work has shown that the martian climate is anything but static, but is almost certainly in a continual state of transient response to slowly varying insolation associated with cyclic variations in its orbit and rotation. We conclude with a discussion of the physical processes underlying these long- term climate variations on Mars, and an overview of some of the most intriguing outstanding problems that should be a focus for future observational and theoretical studies.

The EChO science case


G Tinetti, P Drossart, P Eccleston, P Hartogh, K Isaak, M Linder, C Lovis, G Micela, M Ollivier, L Puig, I Ribas, I Snellen, B Swinyard, F Allard, J Barstow, J Cho, A Coustenis, C Cockell, A Correia, L Decin, R de Kok, P Deroo, T Encrenaz, F Forget, A Glasse, C Griffith, T Guillot, T Koskinen, H Lammer, J Leconte, P Maxted, I Mueller-Wodarg, R Nelson, C North, E Palle, I Pagano, G Piccioni, D Pinfield, F Selsis, A Sozzetti, L Stixrude, J Tennyson, D Turrini, M Zapatero-Osorio, J-P Beaulieu, D Grodent, M Guedel, D Luz, HU Norgaard-Nielsen, T Ray, H Rickman, A Selig, M Swain, M Banaszkiewicz, M Barlow, N Bowles, G Branduardi-Raymont, VC du Foresto, J-C Gerard, L Gizon, A Hornstrup, C Jarchow, F Kerschbaum, G Kovacs, P-O Lagage, T Lim, M Lopez-Morales, G Malaguti, E Pace, E Pascale, B Vandenbussche, G Wright, G Ramos Zapata, A Adriani, R Azzollini, A Balado, I Bryson, R Burston, J Colome, M Crook, A Di Giorgio, M Griffin, R Hoogeveen, R Ottensamer, R Irshad, K Middleton, G Morgante, F Pinsard, M Rataj, J-M Reess, G Savini, J-R Schrader, R Stamper, B Winter, L Abe, M Abreu, N Achilleos, P Ade, V Adybekian, L Affer, C Agnor, M Agundez, C Alard, J Alcala, C Allende Prieto, FJ Alonso Floriano, F Altieri, CA Alvarez Iglesias, P Amado, A Andersen, A Aylward, C Baffa, G Bakos, P Ballerini, M Banaszkiewicz, RJ Barber, D Barrado, EJ Barton, V Batista, G Bellucci, JA Belmonte Aviles, D Berry, B Bezard, D Biondi, M Blecka, I Boisse, B Bonfond, P Borde, P Boerner, H Bouy, L Brown, L Buchhave, J Budaj, A Bulgarelli, M Burleigh, A Cabral, MT Capria, A Cassan, C Cavarroc, C Cecchi-Pestellini, R Cerulli, J Chadney, S Chamberlain, S Charnoz, NC Jessen, A Ciaravella, A Claret, R Claudi, A Coates, R Cole, A Collura, D Cordier, E Covino, C Danielski, M Damasso, HJ Deeg, E Delgado-Mena, C Del Vecchio, O Demangeon, A De Sio, J De Wit, M Dobrijevic, P Doel, C Dominic, E Dorfi, S Eales, C Eiroa, M Espinoza Contreras, M Esposito, V Eymet, N Fabrizio, M Fernandez, B Femena Castella, P Figueira, G Filacchione, L Fletcher, M Focardi, S Fossey, P Fouque, J Frith, M Galand, L Gambicorti, P Gaulme, RJ Garcia Lopez, A Garcia-Piquer, W Gear, J-C Gerard, L Gesa, E Giani, F Gianotti, M Gillon, E Giro, M Giuranna, H Gomez, I Gomez-Leal, J Gonzalez Hernandez, B Gonzalez Merino, R Graczyk, D Grassi, J Guardia, P Guio, J Gustin, P Hargrave, J Haigh, E Hebrard, U Heiter, RL Heredero, E Herrero, F Hersant, D Heyrovsky, M Hollis, B Hubert, R Hueso, G Israelian, N Iro, P Irwin, S Jacquemoud, G Jones, H Jones, K Justtanont, T Kehoe, F Kerschbaum, E Kerins, P Kervella, D Kipping, T Koskinen, N Krupp, O Lahav, B Laken, N Lanza, E Lellouch, G Leto, J Licandro Goldaracena, C Lithgow-Bertelloni, SJ Liu, U Lo Cicero, N Lodieu, P Lognonne, M Lopez-Puertas, MA Lopez-Valverde, IL Rasmussen, A Luntzer, P Machado, C MacTavish, A Maggio, J-P Maillard, W Magnes, J Maldonado, U Mall, J-B Marquette, P Mauskopf, F Massi, A-S Maurin, A Medvedev, C Michaut, P Miles-Paez, M Montalto, P Montanes Rodriguez, M Monteiro, D Montes, H Morais, JC Morales, M Morales-Calderon, G Morello, A Moro Martin, J Moses, A Moya Bedon, F Murgas Alcaino, E Oliva, G Orton, F Palla, M Pancrazzi, E Pantin, V Parmentier, H Parviainen, KY Pena Ramirez, J Peralta, S Perez-Hoyos, R Petrov, S Pezzuto, R Pietrzak, E Pilat-Lohinger, N Piskunov, R Prinja, L Prisinzano, I Polichtchouk, E Poretti, A Radioti, AA Ramos, T Rank-Lueftinger, P Read, K Readorn, R Rebolo Lopez, J Rebordao, M Rengel, L Rezac, M Rocchetto, F Rodler, VJ Sanchez Bejar, AS Lavega, E Sanroma, N Santos, J Sanz Forcada, G Scandariato, F-X Schmider, A Scholz, S Scuderi, J Sethenadh, S Shore, A Showman, B Sicardy, P Sitek, A Smith, L Soret, S Sousa, A Stiepen, M Stolarski, G Strazzulla, HM Tabernero, P Tanga, M Tecsa, J Temple, L Terenzi, M Tessenyi, L Testi, S Thompson, H Thrastarson, BW Tingley, M Trifoglio, J Martin Torres, A Tozzi, D Turrini, R Varley, F Vakili, M de Val-Borro, ML Valdivieso, O Venot, E Villaver, S Vinatier, S Viti, I Waldmann, D Waltham, D Ward-Thompson, R Waters, C Watkins, D Watson, P Wawer, A Wawrzaszek, G White, T Widemann, W Winek, T Wisniowski, R Yelle, Y Yung, SN Yurchenko

A Lorenz/Boer energy budget for the atmosphere of Mars from a "reanalysis" of spacecraft observations

Geophysical Research Letters American Geophysical Union 42 (2015) 8320-8327

F Tabataba-Vakili, PL Read, SR Lewis, L Montabone, T Ruan, Y Wang, A Valeanu, R Young

We calculate a Lorenz energy budget for the Martian atmosphere from reanalysis derived from Mars Global Surveyor data for Mars years 24-27. We present global, annual mean energy and conversion rates per unit area and per unit mass and compare these to Earth data. The directions of the energy conversion terms for Mars are similar to Earth, with the exception of the barotropic conversion between zonal and eddy kinetic energy reservoirs. Further, seasonal and hemispheric decomposition reveals a strong conversion between zonal energy reservoirs over the year, but these balance each other out in global and annual mean. On separating the diurnal timescale, the contribution to the conversion terms and eddy kinetic energy for diurnal and shorter timescales in many cases (especially during planet-encircling dust storms) exceeds the contribution of longer timescales. This suggests that thermal tides have a significant effect on the generation of eddy kinetic energy. Key Points Comprehensive analysis of global and hemispheric energy exchanges within the Mars atmosphere Thermal tides have a significant impact on eddy energy and conversion terms Most conversion occurs in zonal component but is canceled out in annual and global mean