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Jun 29, 2018
06/18

by
I. Polichtchouk; T. G. Shepherd

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The impact of uncertainties in surface layer physics on the atmospheric general circulation is comparatively unexplored. Here the sensitivity of the zonal-mean circulation to reduced air-sea momentum roughness ($Z_{0m}$) at low flow speed is investigated with the Community Atmosphere Model (CAM3). In an aquaplanet framework with prescribed sea surface temperatures, the response to reduced $Z_{0m}$ resembles the La Ni$\tilde{\text{n}}$a minus El Ni$\tilde{\text{n}}$o response to El...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1606.00566

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Jun 29, 2018
06/18

by
D. E. Ruiz; J. B. Parker; E. L. Shi; I. Y. Dodin

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The wave kinetic equation (WKE) describing drift-wave (DW) turbulence is widely used in studies of zonal flows (ZFs) emerging from DW turbulence. However, this formulation neglects the exchange of enstrophy between DWs and ZFs and also ignores effects beyond the geometrical-optics limit. We derive a modified theory that takes both of these effects into account, while still treating DW quanta ("driftons") as particles in phase space. The drifton dynamics is described by an equation of...

Topics: Atmospheric and Oceanic Physics, Physics, Plasma Physics

Source: http://arxiv.org/abs/1608.05373

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Jun 29, 2018
06/18

by
F Bouchet; Antoine Venaille

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Zonal jets are striking and beautiful examples of the propensity for geophysical turbulent flows to spontaneously self-organize into robust, large scale coherent structures. There exist many dynamical mechanisms for the formation of zonal jets: statistical theories (kinetic approaches, second order or larger oder closures), deterministic approaches (modulational instability, $\beta$-plumes, radiating instability, zonostrophic turbulence, and so on). A striking remark is that all these different...

Topics: Atmospheric and Oceanic Physics, Fluid Dynamics, Statistical Mechanics, Physics, Condensed Matter

Source: http://arxiv.org/abs/1602.06714

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Jun 30, 2018
06/18

by
Alexander Bihlo; Scott MacLachlan

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We formulate a general criterion for the exact preservation of the "lake at rest" solution in general mesh-based and meshless numerical schemes for the strong form of the shallow-water equations with bottom topography. The main idea is a careful mimetic design for the spatial derivative operators in the momentum flux equation that is paired with a compatible averaging rule for the water column height arising in the bottom topography source term. We prove consistency of the mimetic...

Topics: Physics, Numerical Analysis, Fluid Dynamics, Computational Physics, Atmospheric and Oceanic...

Source: http://arxiv.org/abs/1702.07749

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Jun 29, 2018
06/18

by
Ravi Shekhar; William R. Boos

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The correlation between increased Sahel rainfall and reduced Saharan surface pressure is well established in observations and global climate models, and has been used to imply that increased Sahel rainfall is caused by a stronger shallow meridional circulation (SMC) over the Sahara. This study uses two atmospheric reanalyses to examine interannual variability of Sahel rainfall and the Saharan SMC, which consists of northward near-surface flow across the Sahel into the Sahara and southward flow...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1609.08515

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Jun 29, 2018
06/18

by
Jai Sukhatme; V. Venugopal

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We begin by providing observational evidence that the probability of encountering very high and very low annual tropical rainfall has increased significantly in the recent decade (1998-present) as compared to the preceding warming era (1979-1997). These changes over land and ocean are spatially coherent and comprise of a rearrangement of very wet regions and a systematic expansion of dry zones. While the increased likelihood of extremes is consistent with a higher average temperature during the...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1604.04050

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Jun 29, 2018
06/18

by
Bruno Issenmann; Claude Laroche; Eric Falcon

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We experimentally study gravity-capillary wave turbulence on the interface between two immiscible fluids of close density with free upper surface. We locally measure the wave height at the interface between both fluids by means of a highly sensitive laser Doppler vibrometer. We show that the inertial range of the capillary wave turbulence regime is significantly extended when the upper fluid depth is increased: The crossover frequency between the gravity and capillary wave turbulence regimes is...

Topics: Fluid Dynamics, Nonlinear Sciences, Atmospheric and Oceanic Physics, Physics, Classical Physics,...

Source: http://arxiv.org/abs/1610.05899

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Jun 30, 2018
06/18

by
Shahrdad G. Sajjadi; Sarena Robertson; Rebecca Harvey; Mary Brown

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The recent analytical of multi-layer analyses proposed by Sajjadi, Hunt and Drullion (2014) (SHD14) is solved numerically for atmospheric turbulent shear fows blowing over unsteady Stokes water waves, of low to moderate steepness. It is demonstrated that as the wave steepens further the inner layer exceeds the critical layer and beneath the cat's-eye there is a strong reverse flow which will then affect the surface drag, but at the surface the flow adjusts itself to the orbital velocity of the...

Topics: Fluid Dynamics, Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1704.01963

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Jun 29, 2018
06/18

by
Yantao Yang; Roberto Verzicco; Detlef Lohse

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Vertically bounded fingering double diffusive convection (DDC) is numerically investigated, focusing on the influences of different velocity boundary conditions, i.e. the no-slip condition which is inevitable in the lab-scale experimental research, and the free-slip condition which is an approximation for the interfaces in many natural environments, such as the oceans. For both boundary conditions the flow is dominated by fingers and the global responses follow the same scaling laws, with...

Topics: Fluid Dynamics, Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1602.07718

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Jun 29, 2018
06/18

by
O. I. Berngardt; N. P. Perevalova; A. V. Podlesnyi; V. I. Kurkin; G. A. Zherebtsov

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Based on the Irkutsk fast monostatic chirp ionosonde data we made a statistical analysis of ionospheric effects for 28 earthquakes which appeared in 2011-2016 years. These effects are related with surface (Rayleigh) seismic waves far from epicenter. The analysis has shown that nine of these earthquakes were accompanied by vertical midscale ionospheric irregularities (multicusp). To estimate the ionospheric efficiency of the seismic waves we proposed new index $K_{W}$. The index estimates the...

Topics: Space Physics, Geophysics, Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1609.08366

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Jun 29, 2018
06/18

by
Christine Kazantsev; Eugene Kazantsev; Mikhail Tolstykh

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The review describes the development of ideas Gury Ivanovich Marchuk in the field of variational data assimilation for ocean models applied in particular in coupled models for long-range weather forecasts. Particular attention is paid to the optimization of boundary conditions on rigid boundaries. As idealized and realistic model configurations are considered. It is shown that the optimization allows us to determine the most sensitive model operators and bring the model solution closer to the...

Topics: Optimization and Control, Mathematics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1601.01193

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Jun 29, 2018
06/18

by
Michael Weniger; Petra Friederichs

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The feature based spatial verification method SAL is applied to cloud data, i.e. two-dimensional spatial fields of total cloud cover and spectral radiance. Model output is obtained from the COSMO-DE forward operator SynSat and compared to SEVIRI satellite data. The aim of this study is twofold. First, to assess the applicability of SAL to this kind of data, and second, to analyze the role of external object identification algorithms (OIA) and the effects of observational uncertainties on the...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1603.01656

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Jun 29, 2018
06/18

by
Krzysztof Chalupka; Tobias Bischoff; Pietro Perona; Frederick Eberhardt

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We show that the climate phenomena of El Nino and La Nina arise naturally as states of macro-variables when our recent causal feature learning framework (Chalupka 2015, Chalupka 2016) is applied to micro-level measures of zonal wind (ZW) and sea surface temperatures (SST) taken over the equatorial band of the Pacific Ocean. The method identifies these unusual climate states on the basis of the relation between ZW and SST patterns without any input about past occurrences of El Nino or La Nina....

Topics: Atmospheric and Oceanic Physics, Machine Learning, Artificial Intelligence, Physics, Learning,...

Source: http://arxiv.org/abs/1605.09370

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Jun 29, 2018
06/18

by
Michael P. Byrne; Paul A. O'Gorman

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Climate models simulate a strong land-ocean contrast in the response of near-surface relative humidity to global warming: relative humidity tends to increase slightly over oceans but decrease substantially over land. Surface energy balance arguments have been used to understand the response over ocean but are difficult to apply over more complex land surfaces. Here, a conceptual box model is introduced, involving moisture transport between the land and ocean boundary layers and...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1605.00380

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1.0

Jun 30, 2018
06/18

by
Mattia Serra; Pratik Sathe; Francisco Beron-Vera; George Haller

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The polar vortices play a crucial role in the formation of the ozone hole and can cause severe weather anomalies. Their boundaries, known as the vortex `edges', are typically identified via methods that are either frame-dependent or return non-material structures, and hence are unsuitable for assessing material transport barriers. Using two-dimensional velocity data on isentropic surfaces in the northern hemisphere, we show that elliptic Lagrangian Coherent Structures (LCSs) identify the...

Topics: Physics, Nonlinear Sciences, Dynamical Systems, Atmospheric and Oceanic Physics, Chaotic Dynamics,...

Source: http://arxiv.org/abs/1702.05593

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Jun 29, 2018
06/18

by
Colin Goldblatt

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Proxima Centauri b, an Earth-size planet in the habitable zone of our nearest stellar neighbour, has just been discovered. A theoretical framework of synchronously rotating planets, in which the risk of a runaway greenhouse on the sunlight side and atmospheric collapse on the reverse side are mutually ameliorated via heat transport is discussed. This is developed via simple (tutorial) models of the climate. These show that lower incident stellar flux means that less heat transport, so less...

Topics: Earth and Planetary Astrophysics, Astrophysics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1608.07263

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Jun 29, 2018
06/18

by
Inderpreet Kaur; Andrea Mentrelli; Frédéric Bosseur; Jean-Baptiste Filippi; Gianni Pagnini

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This paper presents a mathematical approach to model the effects of phenomena with random nature such as turbulence and fire-spotting into the existing wildfire simulators. The formulation proposes that the propagation of the fire-front is the sum of a drifting component (obtained from an existing wildfire simulator without turbulence and fire-spotting) and a random fluctuating component. The modelling of the random effects is embodied in a probability density function accounting for the...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1601.06272

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Jun 30, 2018
06/18

by
Elena Tolkova

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An extensive data set of water level measurements of the September 2015 Chilean tsunami in rivers in Japan and a new methodology for data processing are used to verify that tsunami dissipation in a river at each instant and locality depends on the tidally-modified wave-locked slope of the river surface. As deduced from the observations, a relatively small tsunami or ocean noise traveling at mild wave-locked slopes can propagate virtually without losses to the upstream locations where observed...

Topics: Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1703.09405

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1.0

Jun 29, 2018
06/18

by
Suhas DL; Jai Sukhatme; Joy M. Monteiro

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The response of the nonlinear shallow water equations (SWE) on a sphere to tropical vorticity forcing is examined with an emphasis on momentum fluxes and the emergence of a superrotating (SR) state. Fixing the radiative damping and momentum drag timescales to be of the order of a few days, a state of SR is shown to emerge under steady large-scale and random small-scale vorticity forcing. In the first example, the stationary response to a pair of equal and oppositely signed vortices placed on...

Topics: Fluid Dynamics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1612.01719

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Jun 30, 2018
06/18

by
L. M. Canel; J. I. Katz

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We use an extensive NOAA database of hourly precipitation data from 5995 stations in the 48 contiguous United States over the period 1949--2009 to investigate possible trends in the frequency and severity of extreme weather events, defined as periods of intense precipitation. The frequency and intensity of these events are quantified by a dimensionless storminess, defined as the variance of the hourly rainfall at a site normalized by the square of the mean rainfall at that site. For 1722...

Topics: Physics, Atmospheric and Oceanic Physics, Physics and Society

Source: http://arxiv.org/abs/1701.06993

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Jun 29, 2018
06/18

by
E. Masciadri; B. Neichel; A. Guesalaga; A. Turchi

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Wide Field Adaptive Optics (WFAO) systems represent the more sophisticated AO systems available today at large telescopes. A critical aspect for these WFAO systems in order to deliver an optimised performance is the knowledge of the vertical spatiotemporal distribution of the CN2 and the wind speed. Previous studies (Cortes et al., 2012) already proved the ability of GeMS (the Gemini Multi-Conjugated AO system) in retrieving CN2 and wind vertical stratification using the telemetry data. To...

Topics: Astrophysics, Instrumentation and Methods for Astrophysics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1608.06489

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2.0

Jun 30, 2018
06/18

by
Pierre Delplace; J. B. Marston; Antoine Venaille

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Symmetries and topology are central to an understanding of physics. Topology explains the precise quantization of the Hall effect and the protection of surface states in topological insulators against scattering by non-magnetic impurities or bumps. Recently topologically protected edge excitations have been found in artificial lattice structures that support classical waves of various types. However, the interplay between discrete symmetries and the topology of fluid waves has so far played...

Topics: Physics, Condensed Matter, Astrophysics, Earth and Planetary Astrophysics, Fluid Dynamics,...

Source: http://arxiv.org/abs/1702.07583

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Jun 29, 2018
06/18

by
João M. Mendonça; Simon L. Grimm; Luc Grosheintz; Kevin Heng

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We have designed and developed, from scratch, a global circulation model named THOR that solves the three-dimensional non-hydrostatic Euler equations. Our general approach lifts the commonly used assumptions of a shallow atmosphere and hydrostatic equilibrium. We solve the "pole problem" (where converging meridians on a sphere lead to increasingly smaller time steps near the poles) by implementing an icosahedral grid. Irregularities in the grid, which lead to grid imprinting, are...

Topics: Earth and Planetary Astrophysics, Astrophysics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1607.05535

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1.0

Jun 29, 2018
06/18

by
Renzo Mosetti

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The observed pseudo-periodic reversal of the upper layer circulation of the Ionian Sea has been assumed to be related to some internal feedback processes (density driven) by the so called BiOS (Adriatic-Ionian Bimodal Oscillating System) hypothesis. The mechanism seems to be very well described by a non-linear oscillator dynamical system. By setting the state variables as the salinity of Adriatic deep water and the sea level anomaly in the Ionian region a Van der Pol equation has been obtained....

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1612.05254

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Jun 29, 2018
06/18

by
A. E. Kuchma; A. K. Shchekin; D. S. Martyukova

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A new comprehensive analysis of Stefan's flow caused by a free growing droplet in vapor-gas atmosphere with several condensing components is presented. This analysis, based on the nonstationary heat and material balance and diffusion transport equations, shows the appearance of the Stefan inflow in the vicinity of the growing droplet and the outflow at large distances from the droplet as a consequence of nonisothermal condensation. For an ensemble of droplets in the atmospheric cloud, this flow...

Topics: Soft Condensed Matter, Chemical Physics, Condensed Matter, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1606.02086

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Jun 29, 2018
06/18

by
Eileen Hertwig; Frank Lunkeit; Klaus Fraedrich

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A set of idealized experiments are performed to analyze the competing effects of declining atmospheric CO2 concentrations, the opening of an ocean gateway, and varying orbital parameters. These forcing mechanisms, which influence the global mean climate state, may have played a role for triggering climate transitions of the past (for example during the Eocene-Oligocene climate transition and the build-up of the Antarctic Ice Sheet). Sensitivity simulations with a coupled atmosphere-ocean...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1602.01259

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Jun 29, 2018
06/18

by
Pascal Marquet

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The aim of this note is to derive the mixed-phase version of the moist-air entropy potential temperature $\theta_s$ derived in Marquet (2011). This mixed-phase version is suitable to describe parcels where liquid water and ice are allowed to coexist, with possible under- or super-saturations, with possible supercooled water and with possible different temperatures for dry air and water vapour, on the one hand, condensed water and ice, on the other hand. The impact of this new mixed-phase...

Topics: Geophysics, Fluid Dynamics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1605.04382

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Jun 29, 2018
06/18

by
Ch. Helling; G. Lee; I. Dobbs-Dixon; N. Mayne; D. S. Amundsen; J. Khaimova; A. A. Unger; J. Manners; D. Acreman; C. Smith

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3D atmosphere model results are used to comparatively study the kinetic, non-equilibrium cloud formation in the atmospheres of two example planets guided by the giant gas planets HD209458b and HD189733b. Rather independently of hydrodynamic model differences, our cloud modelling suggests that both planets are covered in mineral clouds throughout the entire modelling domain. Both planets harbour chemically complex clouds that are made of mineral particles that have a height-dependent material...

Topics: Fluid Dynamics, Atmospheric and Oceanic Physics, Solar and Stellar Astrophysics, Physics, Earth and...

Source: http://arxiv.org/abs/1603.04022

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Jun 29, 2018
06/18

by
Pedram Hassanzadeh; Zhiming Kuang

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A linear response function (LRF) relates the mean-response of a nonlinear system to weak external forcings and vice versa. Even for simple models of the general circulation, such as the dry dynamical core, the LRF cannot be calculated from first principles due to the lack of a complete theory for eddy-mean flow feedbacks. According to the Fluctuation-Dissipation Theorem (FDT), the LRF can be calculated using only the covariance and lag-covariance matrices of the unforced system. However,...

Topics: Fluid Dynamics, Nonlinear Sciences, Atmospheric and Oceanic Physics, Data Analysis, Statistics and...

Source: http://arxiv.org/abs/1603.08807

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Jun 29, 2018
06/18

by
Y. Wang; F. J. Beron-Vera; M. J. Olascoaga

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We document the long-term evolution of an Agulhas ring detected from satellite altimetry using a technique from nonlinear dynamical systems that enables objective (i.e., observer-independent) eddy framing. Such objectively detected eddies have Lagrangian (material) boundaries that remain coherent (unfilamented) over the detection period. The ring preserves a quite compact material entity for a period of about 2 years even after most initial coherence is lost within 5 months after detection. We...

Topics: Plasma Physics, Fluid Dynamics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1601.01560

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Jun 30, 2018
06/18

by
Pascal Marquet

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The paper "On the theory of storm" (Zur Sturmtheorie) is the last one Max Margules has published in 1906, just before to "bid farewell to Meteorology" (using his words). The lack of English translation of this paper might be filled by this attempt which can be certainly improved, however.

Topics: History and Philosophy of Physics, Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1704.06128

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Jun 29, 2018
06/18

by
Woosok Moon

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The stochastic Arctic sea ice model described as a single periodic non-autonomous stochastic ordinary differential equation (ODE) is useful in explaining the seasonal variability of Arctic sea ice. However, to be nearer to realistic approximations we consider the inclusion of long-term forcing implying the effect of slowly-varying ocean or atmospheric low-frequencies. In this research, we rely on the equivalent Fokker-Planck equation instead of the stochastic ODE owing to the advantages of the...

Topics: Nonlinear Sciences, Atmospheric and Oceanic Physics, Physics, Mathematics, Chaotic Dynamics,...

Source: http://arxiv.org/abs/1611.00268

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Jun 29, 2018
06/18

by
Colin Goldblatt

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The dominant paradigm in assigning "habitability"' to terrestrial planets is to define a circumstellar habitable zone: the locus of orbital radii in which the planet is neither too hot nor too cold for life as we know it. One dimensional climate models have identified theoretically impressive boundaries for this zone: a runaway greenhouse or water loss at the inner edge (Venus), and low-latitude glaciation followed by formation of CO2 clouds at the outer edge. A cottage industry now...

Topics: Earth and Planetary Astrophysics, Astrophysics, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1603.00950

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Jun 29, 2018
06/18

by
J. B. Marston; G. P. Chini; S. M. Tobias

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Quasilinear theory is often utilized to approximate the dynamics of fluids exhibiting significant interactions between mean flows and eddies. In this paper we present a generalization of quasilinear theory to include dynamic mode interactions on the large scales. This generalized quasilinear (GQL) approximation is achieved by separating the state variables into large and small zonal scales via a spectral filter rather than by a decomposition into a formal mean and fluctuations. Nonlinear...

Topics: Fluid Dynamics, Atmospheric and Oceanic Physics, Solar and Stellar Astrophysics, Physics, Earth and...

Source: http://arxiv.org/abs/1601.06720

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Jun 29, 2018
06/18

by
Daniel A. Shaevitz; Ji Nie; Adam H. Sobel

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Devastating floods in northeast Pakistan and northern India occurred in July 2010 and September 2014 as a consequence of extreme precipitation events. The 2010 and 2014 flood events had similar synoptic flow patterns that led to an anomalously high moisture content in the flood region. The quasi-geostrophic omega equation is inverted in order to attribute components of the large-scale vertical motion profile to synoptic forcing, diabatic heating, and mechanically forced orographic ascent. The...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1603.01317

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Jun 29, 2018
06/18

by
Rui A. P. Perdigão; Carlos A. L. Pires; Julia Hall

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We formulate a nonlinear synergistic theory of coevolutionary systems, disentangling and explaining dynamic complexity in terms of fundamental processes for optimised data analysis and dynamic model design: Dynamic Source Analysis (DSA). DSA provides a nonlinear dynamical basis for spatiotemporal datasets or dynamical models, eliminating redundancies and expressing the system in terms of the smallest number of fundamental processes and interactions without loss of information. This optimises...

Topics: Physics, Dynamical Systems, Atmospheric and Oceanic Physics, Mathematics

Source: http://arxiv.org/abs/1611.03403

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Jun 30, 2018
06/18

by
Hemant Khatri; Jai Sukhatme; Abhishek Kumar; Mahendra K. Verma

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Enstrophy, kinetic energy (KE) fluxes and spectra are estimated in different parts of the mid-latitudinal oceans via altimetry data. To begin with, using geostrophic currents derived from sea-surface height anomaly data provided by AVISO, we confirm the presence of a strong inverse flux of surface KE at scales larger than approximately 250 km. We then compute enstrophy fluxes to help develop a clearer picture of the underlying dynamics at smaller scales, i.e., 250 km to 100 km. Here, we observe...

Topics: Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1701.07966

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Jun 29, 2018
06/18

by
Chongsheng Cao; Jinkai Li; Edriss S. Titi

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In this paper, we consider the initial-boundary value problem of the three-dimensional primitive equations for oceanic and atmospheric dynamics with only horizontal viscosity and horizontal diffusivity. We establish the local, in time, well-posedness of strong solutions, for any initial data $(v_0, T_0)\in H^1$, by using the local, in space, type energy estimate. We also establish the global well-posedness of strong solutions for this system, with any initial data $(v_0, T_0)\in H^1\cap...

Topics: Fluid Dynamics, Atmospheric and Oceanic Physics, Analysis of PDEs, Physics, Mathematics, Geophysics

Source: http://arxiv.org/abs/1607.06252

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Jun 30, 2018
06/18

by
Jonathan Demaeyer; Stéphane Vannitsem

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We review some recent methods of subgrid-scale parameterization used in the context of climate modeling. These methods are developed to take into account (subgrid) processes playing an important role in the correct representation of the atmospheric and climate variability. We illustrate these methods on a simple stochastic triad system relevant for the atmospheric and climate dynamics, and we show in particular that the stability properties of the underlying dynamics of the subgrid processes...

Topics: Physics, Statistical Mechanics, Condensed Matter, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1701.04742

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Jun 29, 2018
06/18

by
Jonathan Demaeyer; Stéphane Vannitsem

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A stochastic subgrid-scale parameterization based on the Ruelle's response theory and proposed in Wouters and Lucarini [2012] is tested in the context of a low-order coupled ocean-atmosphere model for which a part of the atmospheric modes are considered as unresolved. A natural separation of the phase-space into an invariant set and its complement allows for an analytical derivation of the different terms involved in the parameterization, namely the average, the fluctuation and the long memory...

Topics: Statistical Mechanics, Condensed Matter, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1605.00461

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Jun 29, 2018
06/18

by
Juan M. Restrepo; Shankar C. Venkataramani

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We develop a stochastic parametrization, based on a `simple' deterministic model for the dynamics of steady longshore currents, that produces ensembles that are statistically consistent with field observations of these currents. Unlike deterministic models, stochastic parameterization incorporates randomness and hence can only match the observations in a statistical sense. Unlike statistical emulators, in which the model is tuned to the statistical structure of the observation, stochastic...

Topics: Atmospheric and Oceanic Physics, Data Analysis, Statistics and Probability, Physics, Mathematics,...

Source: http://arxiv.org/abs/1612.01046

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3.0

Jun 29, 2018
06/18

by
Georg A. Gottwald; Daan T. Crommelin; Christian L. E. Franzke

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In this chapter we review stochastic modelling methods in climate science. First we provide a conceptual framework for stochastic modelling of deterministic dynamical systems based on the Mori-Zwanzig formalism. The Mori-Zwanzig equations contain a Markov term, a memory term and a term suggestive of stochastic noise. Within this framework we express standard model reduction methods such as averaging and homogenization which eliminate the memory term. We further discuss ways to deal with the...

Topics: Chaotic Dynamics, Nonlinear Sciences, Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1612.07474

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Jun 29, 2018
06/18

by
James B. Elsner; Thomas H. Jagger; Tyler Fricker

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This paper estimates local tornado risk from records of past events using statistical models. First, a spatial model is fit to the tornado counts aggregated in counties with terms that control for changes in observational practices over time. Results provide a long-term view of risk that delineates the main tornado corridors in the United States where the expected annual rate exceeds two tornadoes per 10,000 square km. A few counties in the Texas Panhandle and central Kansas have annual rates...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1606.07325

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2.0

Jun 29, 2018
06/18

by
Srikanth Toppaladoddi; John S. Wettlaufer

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We study the seasonal changes in the thickness distribution of Arctic sea ice, $g(h)$, under climate forcing. Our analytical and numerical approach is based on a Fokker-Planck equation for $g(h)$ (Toppaladoddi \& Wettlaufer \emph{Phys. Rev. Lett.} {\bf 115}, 148501, 2015), in which the thermodynamic growth rates are determined using observed climatology. In particular, the Fokker-Planck equation is coupled to the observationally consistent thermodynamic model of Eisenman \& Wettlaufer...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1611.01045

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2.0

Jun 29, 2018
06/18

by
Anna S. von der Heydt; Peter Ashwin

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Equilibrium climate sensitivity (ECS) is a key predictor of climate change. However, it is not very well constrained, either by climate models or by observational data. The reasons for this include strong internal variability and forcing on many time scales. In practise this means that the 'equilibrium' will only be relative to fixing the slow feedback processes before comparing palaeoclimate sensitivity estimates with estimates from model simulations. In addition, information from the late...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1604.03311

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1.0

Jun 29, 2018
06/18

by
A. L. Virovlyansky

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A method is proposed for finding the wave field components which are weakly sensitive to the sound speed perturbation in the ocean acoustic waveguides. Such a component is formed by a narrow beam of rays whose spread in vertical direction, up to the observation range, remains less than the vertical scale of perturbation. These rays pass through practically the same inhomogeneities and therefore their phases acquire close increments. If the ray amplitudes vary insignificantly, then (i) the...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1610.02568

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0.0

Jun 29, 2018
06/18

by
Michael Weniger; Florian Kapp; Petra Friederichs

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Due to the emergence of new high resolution numerical weather prediction (NWP) models and the availability of new or more reliable remote sensing data, the importance of efficient spatial verification techniques is growing. Wavelet transforms offer an effective framework to decompose spatial data into separate (and possibly orthogonal) scales and directions. Most wavelet based spatial verification techniques have been developed or refined in the last decade and concentrate on assessing forecast...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1605.03395

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0.0

Jun 29, 2018
06/18

by
Mohamed Laib; Mikhail Kanevski

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This paper presents an initial exploration of high frequency records of extreme wind speed in two steps. The first consists in finding the suitable extreme distribution for $120$ measuring stations in Switzerland, by comparing three known distributions: Weibull, Gamma, and Generalized extreme value. This comparison serves as a basis for the second step which applies a spatial modelling by using Extreme Learning Machine. The aim is to model distribution parameters by employing a high dimensional...

Topics: Data Analysis, Statistics and Probability, Physics, Atmospheric and Oceanic Physics

Source: http://arxiv.org/abs/1609.05012

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Jun 29, 2018
06/18

by
Niklas Brännström; Leif Å Persson

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We consider a bilevel optimatisation method for inverse linear atmospheric dispersion problems where both linear and non-linear model parameters are to be determined. We propose that a smooth weighted Mahalanobis distance function is used and derive sufficient conditions for when the follower problem has local strict convexity. A few toy-models are presented where local strict convexity and ill-posedness of the inverse problem are explored, indeed the smooth distance function is compared and...

Topics: Atmospheric and Oceanic Physics, Physics

Source: http://arxiv.org/abs/1607.04804

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Jun 30, 2018
06/18

by
Z. C. Feng; Y. Charles Li

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Short term unpredictability is discovered numerically for high Reynolds number fluid flows under periodic boundary conditions. Furthermore, the abundance of the short term unpredictability is also discovered. These discoveries support our theory that fully developed turbulence is constantly driven by such short term unpredictability.

Topics: Physics, Fluid Dynamics, Nonlinear Sciences, Analysis of PDEs, Atmospheric and Oceanic Physics,...

Source: http://arxiv.org/abs/1702.02993