Wave number selection in the presence of noise: Experimental results

Chaos 28 (2018)

D Zhilenko, O Krivonosova, M Gritsevich, P Read

© 2018 Author(s). In this study, we consider how the wave number selection in spherical Couette flow, in the transition to azimuthal waves after the first instability, occurs in the presence of noise. The outer sphere was held stationary, while the inner sphere rotational speed was increased linearly from a subcritical flow to a supercritical one. In a supercritical flow, one of two possible flow states, each with different azimuthal wave numbers, can appear depending upon the initial and final Reynolds numbers and the acceleration value. Noise perturbations were added by introducing small disturbances into the rotational speed signal. With an increasing noise amplitude, a change in the dominant wave number from m to m ± 1 was found to occur at the same initial and final Reynolds numbers and acceleration values. The flow velocity measurements were conducted by using laser Doppler anemometry. Using these results, the role of noise as well as the behaviour of the amplitudes of the competing modes in their stages of damping and growth were determined.

Meat consumption, health, and the environment.

Science (New York, N.Y.) 361 (2018)

HCJ Godfray, P Aveyard, T Garnett, JW Hall, TJ Key, J Lorimer, RT Pierrehumbert, P Scarborough, M Springmann, SA Jebb

Both the global average per capita consumption of meat and the total amount of meat consumed are rising, driven by increasing average individual incomes and by population growth. The consumption of different types of meat and meat products has substantial effects on people's health, and livestock production can have major negative effects on the environment. Here, we explore the evidence base for these assertions and the options policy-makers have should they wish to intervene to affect population meat consumption. We highlight where more research is required and the great importance of integrating insights from the natural and social sciences.

Impact splash chondrule formation during planetesimal recycling

Icarus 302 (2018) C

T Lichtenberg, GJ Golabek, CP Dullemond, M Schönbächler, TV Gerya, MR Meyer

Late metal–silicate separation on the IAB parent asteroid: Constraints from combined W and Pt isotopes and thermal modelling

Earth and Planetary Science Letters 482 (2018) C

AC Hunt, DL Cook, T Lichtenberg, PM Reger, M Ek, GJ Golabek, M Schönbächler

A Chorus of the WindsOn Saturn!


PL Read

Atmospheric Dynamics of Terrestrial Planets

in Handbook of Exoplanets, Springer International Publishing (2018) 1-31

PL Read, SR Lewis, GK Vallis

The Influence of a Substellar Continent on the Climate of a Tidally Locked Exoplanet

The Astrophysical Journal 854 (2018) 171-171

NT Lewis, FH Lambert, IA Boutle, NJ Mayne, J Manners, DM Acreman

Descent Rate Models of the Synchronization of the Quasi-Biennial Oscillation by the Annual Cycle in Tropical Upwelling


K Rajendran, IM Moroz, SM Osprey, PL Read

Exploring the Atmosphere of Neoproterozoic Earth: The Effect of O-2 on Haze Formation and Composition


SM Horst, C He, MS Ugelow, AM Jellinek, RT Pierrehumbert, MA Tolbert

Superrotation on Venus, on Titan, and Elsewhere


PL Read, S Lebonnois

Comparative terrestrial atmospheric circulation regimes in simplified global circulation models. Part I: From cyclostrophic super-rotation to geostrophic turbulence

Quarterly Journal of the Royal Meteorological Society (2018)

Y Wang, PL Read, F Tabataba-Vakili, RMB Young

© 2018 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society. The regimes of possible global atmospheric circulation patterns in an Earth-like atmosphere are explored using a simplified Global Circulation Model (GCM) based on the University of Hamburg's Portable University Model for the Atmosphere (PUMA)—with simplified (linear) boundary-layer friction, a Newtonian cooling scheme, and dry convective adjustment (designated here as PUMA-S). A series of controlled experiments is conducted by varying planetary rotation rate and imposed equator-to-pole temperature difference. These defining parameters are combined further with each other into dimensionless forms to establish a parameter space in which the occurrences of different circulation regimes are mapped and classified. Clear, coherent trends are found when varying planetary rotation rate (thermal Rossby number) and frictional and thermal relaxation time-scales. The sequence of circulation regimes as a function of parameters, such as the planetary rotation rate, strongly resembles that obtained in laboratory experiments on rotating, stratified flows, especially if a topographic β-effect is included in those experiments to emulate the planetary vorticity gradients in an atmosphere induced by the spherical curvature of the planet. A regular baroclinic wave regime is also obtained at intermediate values of thermal Rossby number and its characteristics and dominant zonal wavenumber depend strongly on the strength of radiative and frictional damping. These regular waves exhibit some strong similarities to baroclinic storms observed on Mars under some conditions. Multiple jets are found at the highest rotation rates, when the Rossby deformation radius and other eddy-related length-scales are much smaller than the radius of the planet. These exhibit some similarity to the multiple zonal jets observed on gas giant planets. Jets form on a scale comparable to the most energetic eddies and the Rhines scale poleward of the supercritical latitude. The balance of heat transport varies strongly with Ω∗ between eddies and zonally symmetric flows, becoming weak with fast rotation.

Comparative terrestrial atmospheric circulation regimes in simplified global circulation models. Part II: Energy budgets and spectral transfers

Quarterly Journal of the Royal Meteorological Society (2018)

PL Read, F Tabataba-Vakili, Y Wang, P Augier, E Lindborg, A Valeanu, RMB Young

© 2018 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society. The energetics of possible global atmospheric circulation patterns in an Earth-like atmosphere are explored using a simplified global General Circulation Model (GCM) based on the University of Hamburg's Portable University Model for the Atmosphere (designated here as PUMA-S), forced by linear relaxation towards a prescribed temperature field and subject to Rayleigh surface drag and hyperdiffusive dissipation. Results from a series of simulations, obtained by varying planetary rotation rate Ω with an imposed equator-to-pole temperature difference, were analysed to determine the structure and magnitude of the heat transport and other contributions to the energy budget for the time-averaged, equilibrated flow. These show clear trends with rotation rate, with the most intense Lorenz energy cycle for an Earth-sized planet occurring with a rotation rate around half that of the present-day Earth (i.e., Ω∗ = Ω/ΩE = 1/2, where ΩE is the rotation rate of the Earth). Kinetic energy (KE) and available potential energy (APE) spectra, E K(n) and E A(n) (where n is total spherical wavenumber), also show clear trends with rotation rate, with n −3 enstrophy-dominated spectra around Ω∗ = 1 and steeper (∼n −5) slopes in the zonal mean flow with little evidence for the n −5/3 spectrum anticipated for an inverse KE cascade. Instead, both KE and APE spectra become almost flat at scales larger than the internal Rossby radius, L d, and exhibit near-equipartition at high wavenumbers. At Ω∗ < <1, the spectrum becomes dominated by KE with E K(n)∼(2–3)E A(n) at most wavenumbers and a slope that tends towards n −5/3 across most of the spectrum. Spectral flux calculations show that enstrophy and APE are almost always cascaded downscale, regardless of rotation rate. KE cascades are more complicated, however, with downscale transfers across almost all wavenumbers, dominated by horizontally divergent modes, for Ω∗ ≲ 1/4. At higher rotation rates, transfers of KE become increasingly dominated by rotational (horizontally nondivergent) components with strong upscale transfers (dominated by eddy–zonal flow interactions) for scales larger than L d and weaker downscale transfers for scales smaller than L d.

Global or Local Pure Condensible Atmospheres: Importance of Horizontal Latent Heat Transport


F Ding, RT Pierrehumbert

A chemical survey of exoplanets with ARIEL


G Tinetti, P Drossart, P Eccleston, P Hartogh, A Heske, J Leconte, G Micela, M Ollivier, G Pilbratt, L Puig, D Turrini, B Vandenbussche, P Wolkenberg, J-P Beaulieu, LA Buchave, M Ferus, M Griffin, M Guedel, K Justtanont, P-O Lagage, P Machado, G Malaguti, M Min, HU Norgaard-Nielsen, M Rataj, T Ray, I Ribas, M Swain, R Szabo, S Werner, J Barstow, M Burleigh, J Cho, VC du Foresto, A Coustenis, L Decin, T Encrenaz, M Galand, M Gillon, R Helled, J Carlos Morales, AG Munoz, A Moneti, I Pagano, E Pascale, G Piccioni, D Pinfield, S Sarkar, F Selsis, J Tennyson, A Triaud, O Venot, I Waldmann, D Waltham, G Wright, J Amiaux, J-L Augueres, M Berthe, N Bezawada, G Bishop, N Bowles, D Coffey, J Colome, M Crook, P-E Crouzet, V Da Peppo, IE Sanz, M Focardi, M Frericks, T Hunt, R Kohley, K Middleton, G Morgante, R Ottensamer, E Pace, C Pearson, R Stamper, K Symonds, M Rengel, E Renotte, P Ade, L Affer, C Alard, N Allard, F Altieri, Y Andre, C Arena, I Argyriou, A Aylward, C Baccani, G Bakos, M Banaszkiewicz, M Barlow, V Batista, G Bellucci, S Benatti, P Bernardi, B Bezard, M Blecka, E Bolmont, B Bonfond, R Bonito, AS Bonomo, JR Brucato, AS Brun, I Bryson, W Bujwan, S Casewell, B Charnay, CC Pestellini, G Chen, A Ciaravella, R Claudi, R Cledassou, M Damasso, M Damiano, C Danielski, P Deroo, AM Di Giorgio, C Dominik, V Doublier, S Doyle, R Doyon, B Drummond, B Duong, S Eales, B Edwards, M Farina, E Flaccomio, L Fletcher, F Forget, S Fossey, M Fraenz, Y Fujii, A Garcia-Piquer, W Gear, H Geoffray, JC Gerard, L Gesa, H Gomez, R Graczyk, C Griffith, D Grodent, MG Guarcello, J Gustin, K Hamano, P Hargrave, Y Hello, K Heng, E Herrero, A Hornstrup, B Hubert, S Ida, M Ikoma, N Iro, P Irwin, C Jarchow, J Jaubert, H Jones, Q Julien, S Kameda, F Kerschbaum, P Kervella, T Koskinen, M Krijger, N Krupp, M Lafarga, F Landini, E Lellouch, G Leto, A Luntzer, T Rank-Luftinger, A Maggio, J Maldonado, J-P Maillard, U Mall, J-B Marquette, S Mathis, P Maxted, T Matsuo, A Medvedev, Y Miguel, V Minier, G Morello, A Mura, N Narita, V Nascimbeni, N Nguyen Tong, V Noce, F Oliva, E Palle, P Palmer, M Pancrazzi, A Papageorgiou, V Parmentier, M Perger, A Petralia, S Pezzuto, R Pierrehumbert, I Pillitteri, G Piotto, G Pisano, L Prisinzano, A Radioti, J-M Reess, L Rezac, M Rocchetto, A Rosich, N Sanna, A Santerne, G Savini, G Scandariato, B Sicardy, C Sierra, G Sindoni, K Skup, I Snellen, M Sobiecki, L Soret, A Sozzetti, A Stiepen, A Strugarek, J Taylor, W Taylor, L Terenzi, M Tessenyi, A Tsiaras, C Tucker, D Valencia, G Vasisht, A Vazan, F Vilardell, S Vinatier, S Viti, R Waters, P Wawer, A Wawrzaszek, A Whitworth, YL Yung, SN Yurchenko, MR Zapatero Osorio, R Zellem, T Zingales, F Zwart

A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex.

Nature communications 9 (2018) 3564-

LN Fletcher, GS Orton, JA Sinclair, S Guerlet, PL Read, A Antuñano, RK Achterberg, FM Flasar, PGJ Irwin, GL Bjoraker, J Hurley, BE Hesman, M Segura, N Gorius, A Mamoutkine, SB Calcutt

Saturn's polar stratosphere exhibits the seasonal growth and dissipation of broad, warm vortices poleward of ~75° latitude, which are strongest in the summer and absent in winter. The longevity of the exploration of the Saturn system by Cassini allows the use of infrared spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres. Although the NPSV formed during late northern spring, by the end of Cassini's reconnaissance (shortly after northern summer solstice), it still did not display the contrasts in temperature and composition that were evident at the south pole during southern summer. The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near 78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible for Saturn's long-lived polar hexagon-which was previously expected to be trapped in the troposphere-can influence the stratospheric temperatures some 300 km above Saturn's clouds.

A rotating annulus driven by localized convective forcing: a new atmosphere-like experiment


H Scolan, PL Read

Was Planet 9 captured in the Sun’s natal star-forming region?

Monthly Notices of the Royal Astronomical Society: Letters 472 (2017) L75-L79

RJ Parker, T Lichtenberg, SP Quanz

Phase synchronization of baroclinic waves in a differentially heated rotating annulus experiment subject to periodic forcing with a variable duty cycle.

Chaos (Woodbury, N.Y.) 27 (2017) 127001-

PL Read, X Morice-Atkinson, EJ Allen, AA Castrejón-Pita

A series of laboratory experiments in a thermally driven, rotating fluid annulus are presented that investigate the onset and characteristics of phase synchronization and frequency entrainment between the intrinsic, chaotic, oscillatory amplitude modulation of travelling baroclinic waves and a periodic modulation of the (axisymmetric) thermal boundary conditions, subject to time-dependent coupling. The time-dependence is in the form of a prescribed duty cycle in which the periodic forcing of the boundary conditions is applied for only a fraction δ of each oscillation. For the rest of the oscillation, the boundary conditions are held fixed. Two profiles of forcing were investigated that capture different parts of the sinusoidal variation and δ was varied over the range 0.1≤δ≤1. Reducing δ was found to act in a similar way to a reduction in a constant coupling coefficient in reducing the width of the interval in forcing frequency or period over which complete synchronization was observed (the "Arnol'd tongue") with respect to the detuning, although for the strongest pulse-like forcing profile some degree of synchronization was discernible even at δ=0.1. Complete phase synchronization was obtained within the Arnol'd tongue itself, although the strength of the amplitude modulation of the baroclinic wave was not significantly affected. These experiments demonstrate a possible mechanism for intraseasonal and/or interannual "teleconnections" within the climate system of the Earth and other planets that does not rely on Rossby wave propagation across the planet along great circles.

Ertel potential vorticity versus Bernoulli streamfunction on Mars


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

Observational evidence against strongly stabilizing tropical cloud feedbacks


IN Williams, RT Pierrehumbert