SEARCH · Searcharxiv

Results for “physics.ao-ph”

Search indexed arXiv papers on artificial intelligence, large language models, computer vision and robotics. Read source abstracts and follow links to arXiv.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

arXiv2012

Dynamical traps and chaotic advection in a meandering jet flow

We continue our study of chaotic mixing and transport of passive particles in a simple model of a meandering jet flow [Prants, et al, Chaos {\bf 16}, 033117 (2006)]. In the present paper we study and explain phenomenologically a connection between dynamical, topological, and statistical properties of chaotic mixing and transport in the model flow in terms of dynamical traps, singular zones in the phase space where particles may spend arbitrary long but finite time [Zaslavsky, Phys. D {\bf 168--169}, 292 (2002)]. The transport of passive particles is described in terms of lengths and durations of zonal flights which are events between two successive changes of sign of zonal velocity. Some peculiarities of the respective probability density functions for short flights are proven to be caused by the so-called rotational-islands traps connected with the boundaries of resonant islands (including those of the vortex cores) filled with the particles moving in the same frame. Whereas, the statistics of long flights can be explained by the influence of the so-called ballistic-islands traps filled with the particles moving from a frame to frame.

nlin.CD↗

arXiv2007

Wind instability of a foam layer sandwiched between the atmosphere and the ocean

Wind shortwave instability of a foam layer between the atmosphere and the ocean is examined in order to reach greater understanding of the recent findings of the decrease in momentum transfer from hurricane winds to sea waves. The three-fluid configuration with the high contrasts in densities of the air, foam and water provides for an effective mechanism to stabilize the water surface.

physics.ao-ph↗

arXiv2007

Kalman Filtering in the Presence of State Space Equality Constraints

We discuss two separate techniques for Kalman Filtering in the presence of state space equality constraints. We then prove that despite the lack of similarity in their formulations, under certain conditions, the two methods result in mathematically equivalent constrained estimate structures. We conclude that the potential benefits of using equality constraints in Kalman Filtering often outweigh the computational costs, and as such, equality constraints, when present, should be enforced by way of one of these two methods.

physics.ao-ph↗

arXiv2007

Signatures of fractal clustering of aerosols advected under gravity

Aerosols under chaotic advection often approach a strange attractor. They move chaotically on this fractal set but, in the presence of gravity, they have a net vertical motion downwards. In practical situations, observational data may be available only at a given level, for example at the ground level. We uncover two fractal signatures of chaotic advection of aerosols under the action of gravity. Each one enables the computation of the fractal dimension $D_{0}$ of the strange attractor governing the advection dynamics from data obtained solely at a given level. We illustrate our theoretical findings with a numerical experiment and discuss their possible relevance to meteorology.

nlin.CD↗

arXiv2007

A jelly model for a ball of an extremely hot plasma

A simple model is applied to study a high temperature rather dense plasma ball. It is assumed that the ions and delocalized electrons are distributed uniformly throughout the ball, and extra/missing charge is found in a thin layer on the surface of a ball. It is shown in the framework of this model that regarded plasma ball can be relatively stable as a metastable state. Calculations show that electrostatic forces, repulsive forces between the ions, and atmospheric pressure can provide stability of a plasma ball. Presented model could be useful to understand the nature of a ball lightning.

physics.plasm-ph↗

arXiv2007

Global Sea Level Stabilization-Sand Dune Fixation: A Solar-powered Sahara Seawater Textile Pipeline

Could anthropogenic saturation with pumped seawater of the porous ground of active sand dune fields in major deserts (e.g., the westernmost Sahara) cause a beneficial reduction of global sea level? Seawater extraction from the ocean, and its deposition on deserted sand dune fields in Mauritania and elsewhere via a Solar-powered Seawater Textile Pipeline (SSTP) can thwart the postulated future global sea level. Thus, Macro-engineering offers an additional cure for anticipated coastal change, driven by global sea level rise, that could supplement, or substitute for (1) stabilizing the shoreline with costly defensive public works (armoring macroprojects) and (2) permanent retreat from the existing shoreline (real and capital property abandonment). We propose Macro-engineering use tactical technologies that sculpt and vegetate barren near-coast sand dune fields with seawater, seawater that would otherwise, as commonly postulated, enlarge Earth seascape area! Our Macro-engineering speculation blends eremology with hydrogeology and some hydromancy. We estimate its cost at 1 billion dollars - about 0.01 per sent of the USA 2007 Gross Domestic Product.

physics.gen-ph↗

arXiv2012

Atmospheric instability as a loss of a metastable equilibrium

General thermodynamic theory of metastable states is used in this short note to try to understand better atmospheric instabilities. It is shown that not only cooling of a cloud can lead to rain, but heating also, especially when there are charged water drops in a cloud (in this case we have rain with lightning). The influence of the global warming on weather is discussed.

physics.ao-ph↗

arXiv2007

The climate version of the Eta regional forecast model. 1. Evaluation of consistency between the Eta model and HadAM3P global model

The regional climate model prepared from Eta WS forecast model has been integrated over South America with the horizontal resolution of 40 km for the period of 1960-1990. The model was forced at its lateral boundaries by the outputs of HadAM3P. The data of HadAM3P represent simulation of modern climate with the resolution about 150 km. In order to prepare climate regional model from the Eta forecast model multiple modifications and corrections were made in the original model. The run of climate Eta model was made on the supercomputer SX-6. The detailed analysis of the results of dynamical downscaling experiment includes an investigation of a consistency between the regional and AGCM models as well as of ability of the regional model to resolve important features of climate fields on the finer scale than that resolved by AGCM. In this work the results of the investigation of a consistency between the output fields of the Eta model and HadAM3P are presented. The geopotential, temperature and wind fields of both models were analysed. For the evaluation of the likeness of these two models outputs,there were used Fourier analysis of time series, consistency index, constituted from linear regression coefficients, time mean and space mean models' arithmetic difference and root mean square difference, dispersion analysis,and some others characteristics. This investigation demonstrates that there are not significant differences in behaviour and spatial arragement of large-scale structures of the two models. Also, the regional model characteristics do not have considerable positive or negative trend during integration time in relation to the global model characteristics. From the total analysis we can affirm that in the description of large-scale climate structures these two models are in consistency.

physics.ao-ph↗

arXiv2009

Local and Nonlocal Dispersive Turbulence

We consider the evolution of a family of 2D dispersive turbulence models. The members of this family involve the nonlinear advection of a dynamically active scalar field, the locality of the streamfunction-scalar relation is denoted by $α$, with smaller $α$ implying increased locality. The dispersive nature arises via a linear term whose strength is characterized by a parameter $ε$. Setting $0 < ε\le 1$, we investigate the interplay of advection and dispersion for differing degrees of locality. Specifically, we study the forward (inverse) transfer of enstrophy (energy) under large-scale (small-scale) random forcing. Straightforward arguments suggest that for small $α$ the scalar field should consist of progressively larger eddies, while for large $α$ the scalar field is expected to have a filamentary structure resulting from a stretch and fold mechanism. Confirming this, we proceed to forced/dissipative dispersive numerical experiments under weakly non-local to local conditions. For $ε\sim 1$, there is quantitative agreement between non-dispersive estimates and observed slopes in the inverse energy transfer regime. On the other hand, forward enstrophy transfer regime always yields slopes that are significantly steeper than the corresponding non-dispersive estimate. Additional simulations show the scaling in the inverse regime to be sensitive to the strength of the dispersive term : specifically, as $ε$ decreases, the inertial-range shortens and we also observe that the slope of the power-law decreases. On the other hand, for the same range of $ε$ values, the forward regime scaling is fairly universal.

physics.flu-dyn↗

arXiv2007

A General Strategy for Physics-Based Model Validation Illustrated with Earthquake Phenomenology, Atmospheric Radiative Transfer, and Computational Fluid Dynamics

Validation is often defined as the process of determining the degree to which a model is an accurate representation of the real world from the perspective of its intended uses. Validation is crucial as industries and governments depend increasingly on predictions by computer models to justify their decisions. In this article, we survey the model validation literature and propose to formulate validation as an iterative construction process that mimics the process occurring implicitly in the minds of scientists. We thus offer a formal representation of the progressive build-up of trust in the model, and thereby replace incapacitating claims on the impossibility of validating a given model by an adaptive process of constructive approximation. This approach is better adapted to the fuzzy, coarse-grained nature of validation. Our procedure factors in the degree of redundancy versus novelty of the experiments used for validation as well as the degree to which the model predicts the observations. We illustrate the new methodology first with the maturation of Quantum Mechanics as the arguably best established physics theory and then with several concrete examples drawn from some of our primary scientific interests: a cellular automaton model for earthquakes, an anomalous diffusion model for solar radiation transport in the cloudy atmosphere, and a computational fluid dynamics code for the Richtmyer-Meshkov instability. This article is an augmented version of Sornette et al. [2007] that appeared in Proceedings of the National Academy of Sciences in 2007 (doi: 10.1073/pnas.0611677104), with an electronic supplement at URL http://www.pnas.org/cgi/content/full/0611677104/DC1. Sornette et al. [2007] is also available in preprint form at physics/0511219.

physics.comp-ph↗

arXiv2008

An Initial Assessment of the GOES Microburst Windspeed Potential Index

A suite of products has been developed and evaluated to assess hazards presented by convective downbursts to aircraft in flight derived from the current generation of Geostationary Operational Environmental Satellite. The existing suite of GOES microburst products employs the GOES sounder to calculate risk based on conceptual models of favorable environmental profiles for convective downburst generation. Large output values of the microburst index algorithms indicate that the ambient thermodynamic structure of the troposphere fits the prototypical environment for each respective microburst type. Accordingly, a new diagnostic nowcasting product, the Microburst Windspeed Potential Index, is derived from merging existing algorithms and designed to quantify the most relevant factors in convective downburst generation in intermediate thermodynamic environments. This paper provides an initial assessment of the MWPI algorithm, presents case studies demonstrating effective operational use of the MWPI product, and presents validation results for the 2007 convective season.

physics.ao-ph↗

arXiv2008

Application of afxy-code for parameterization of ionization yield function Y in the atmosphere for primary cosmic ray protons

In this work is obtained new approximation for the yield function Y for cosmic ray induced ionization in the Earth atmosphere on the basis of simulated data. The parameterization is obtained using inverse nonlinear problem solution with afxy(analyze fx=y)-code. Short description of the methods is given. The found approximation is for primary proton nuclei, inclined up to 70 degrees zenith angle. This permits to estimate the direct ionization by primary cosmic rays explicitly. The parameterization is applicable to the entire atmosphere, from ground level to upper atmosphere. Several implications of the found parameterization are discussed.

physics.space-ph↗

arXiv2008

Cheap Artificial AB-Mountains, Extraction of Water and Energy from Atmosphere and Change of Regional Climate

Author suggests and researches a new revolutionary method for changing the climates of entire countries or portions thereof, obtaining huge amounts of cheap water and energy from the atmosphere. In this paper is presented the idea of cheap artificial inflatable mountains, which may cardinally change the climate of a large region or country. Additional benefits: The potential of tapping large amounts of fresh water and energy. The mountains are inflatable semi-cylindrical constructions from thin film (gas bags) having heights of up to 3 - 5 km. They are located perpendicular to the main wind direction. Encountering these artificial mountains, humid air (wind) rises to crest altitude, is cooled and produces rain (or rain clouds). Many natural mountains are sources of rivers, and other forms of water and power production - and artificial mountains may provide these services for entire nations in the future. The film of these gasbags is supported at altitude by small additional atmospheric overpressure and may be connected to the ground by thin cables. The author has shown (in previous works about the AB-Dome) that this closed AB-Dome allows full control of the weather inside the Dome (the day is always fine, the rain is only at night, no strong winds) and influence to given region. This is a realistic and cheap method of economical irrigation, getting energy and virtual weather control on Earth at the current time.

physics.gen-ph↗

arXiv2008

About the annual distribution of magnetically disturbed cloudless days and nights over Abastumani (41.75N, 42.82E)

The annual distribution of the planetary geomagnetic Ap index monthly mean values on visually cloudless days and nights at the Abastumani Astrophysical Observatory (41.75N, 42.82E) in 1957-1993 is analyzed. Cloudless days were selected from day-time observations of the total ozone content and cloudless nights from night-time measurements of the mesosphere-thermosphere nightglow intensity. Both series of observations were carried out almost uninterrupted during the referred time period. The distribution of long-term monthly mean Ap values on cloudless days shows a semi-annual variation with maxima on the equinoctial months (March and September), while on cloudless nights it displays a seasonal-like character. The semi-annual and seasonal-like variations of Ap modulate the annual distribution of long-term monthly numbers of cloudless days with maximum in August and that of cloudless nights with maximum in September. The lowest monthly mean Ap value for cloudless days and its highest value for cloudless nights fall on June. Different annual distributions of long-term monthly numbers of cloudless days and nights, when sudden storm commencements are present, have been found. This coupling between the visually cloudless days/nights and the magnetically disturbed days may be considered as a manifestation of the influence of space weather/cosmic factors on the regional and global climate.

astro-ph↗

arXiv2008

A GOES imager-derived microburst product

A new multispectral Geostationary Operational Environmental Satellite (GOES) imager product has been developed to assess downburst potential over the western United States employing brightness temperature differences (BTD) between band 3 (upper level water vapor), band 4 (longwave infrared window), and split window band 5. Band 3 is intended to indicate mid to upper-level moisture content and advection while band 5 indicates low-level moisture content. Large BTDs between bands 3 and 5 imply a large relative humidity gradient between the mid-troposphere and the surface, a condition favorable for strong convective downdraft generation due to evaporational cooling of precipitation in the deep sub-cloud layer. In addition, small BTDs between bands 4 and 5 indicate a relatively dry surface layer with solar heating in progress. This paper will outline the development of the GOES-West imager microburst product and present case studies that feature example images, outline potential operational use and assess performance of the algorithm.

physics.ao-ph↗

arXiv2008

Rayleigh-Bénard Convection as a Nambu-metriplectic problem

The traditional Hamiltonian structure of the equations governing conservative Rayleigh-Bénard convection (RBC) is singular, i.e. it's Poisson bracket possesses nontrivial Casimir functionals. We show that a special form of one of these Casimirs can be used to extend the bilinear Poisson bracket to a trilinear generalised Nambu bracket. It is further shown that the equations governing dissipative RBC can be written as the superposition of the conservative Nambu bracket with a dissipative symmetric bracket. This leads to a Nambu-metriplectic system, which completes the geometrical picture of RBC.

physics.flu-dyn↗

arXiv2008

Climate Networks around the Globe are Significantly Effected by El Nino

The temperatures in different zones in the world do not show significant changes due to El-Nino except when measured in a restricted area in the Pacific Ocean. We find, in contrast, that the dynamics of a climate network based on the same temperature records in various geographical zones in the world is significantly influenced by El-Nino. During El-Nino many links of the network are broken, and the number of surviving links comprises a specific and sensitive measure for El-Nino events. While during non El-Nino periods these links which represent correlations between temperatures in different sites are more stable, fast fluctuations of the correlations observed during El-Nino periods cause the links to break.

physics.ao-ph↗

arXiv2009

Microburst windspeed potential assessment: progress and developments

A suite of products has been developed and evaluated to assess hazards presented by convective downbursts to aircraft in flight derived from the current generation of GOES. The existing suite of GOES microburst products employs the sounder to calculate risk based on conceptual models of favorable environmental profiles for convective downburst generation. Accordingly, a diagnostic nowcasting product, the Microburst Windspeed Potential Index, is designed to infer attributes of a favorable microburst environment. In addition, a GOES-West imager microburst algorithm that employs brightness temperature differences between band 3 (upper level water vapor), band 4 (longwave infrared window), and split window band 5 has been developed to supplement the sounder-derived products. This paper provides an updated assessment of the sounder MWPI and imager microburst algorithms, presents case studies demonstrating effective operational use of the microburst products, and presents validation results for the 2008 convective season over United States Great Plains and Great Basin regions.

physics.ao-ph↗