The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Masoud Rostami - One of the best experts on this subject based on the ideXlab platform.
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Geostrophic adjustment on the equatorial Beta-Plane revisited
Physics of Fluids, 2019Co-Authors: Masoud Rostami, V. ZeitlinAbstract:Abstract The process of geostrophic adjustment of localized large-scale pressure anomalies in the standard adiabatic shallow-water model on the equatorial Beta-Plane is revisited, and it is shown that the standard scenario of generation of westward-moving Rossby and eastward-moving Kelvin waves, which underlies the classical Gill theory of tropical circulation due to a localized heating, is not unique. Depending on the strength and aspect ratio of the initial perturbation, the response to the initial perturbation in the western sector can be dominated by inertia-gravity waves. The adjustment in the diabatic moist-convective shallow water model can be totally different and produces, depending on parameters, either Gill-like response or eastward-moving coherent dipolar structures of the type of equatorial modons, which do not appear in the “dry” adjustment, or vortices traveling, respectively, northwest in the Northern and southwest in the Southern hemispheres.
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Geostrophic adjustment on the equatorial Beta-Plane revisited
Physics of Fluids, 2019Co-Authors: Masoud Rostami, Vladimir ZeitlinAbstract:The process of geostrophic adjustment of localized large-scale pressure anomalies in the standard adiabatic shallow-water model on the equatorial Beta-Plane is revisited, and it is shown that the standard scenario of generation of westward-moving Rossby and eastward-moving Kelvin waves, which underlies the classical Gill theory of tropical circulation due to a localized heating, is not unique. Depending on the strength and aspect ratio of the initial perturbation, the response to the initial perturbation in the western sector can be dominated by inertia-gravity waves. The adjustment in the diabatic moist-convective shallow water model can be totally different and produces, depending on parameters, either Gill-like response or eastward-moving coherent dipolar structures of the type of equatorial modons, which do not appear in the “dry” adjustment, or vortices traveling, respectively, northwest in the Northern and southwest in the Southern hemispheres.The process of geostrophic adjustment of localized large-scale pressure anomalies in the standard adiabatic shallow-water model on the equatorial Beta-Plane is revisited, and it is shown that the standard scenario of generation of westward-moving Rossby and eastward-moving Kelvin waves, which underlies the classical Gill theory of tropical circulation due to a localized heating, is not unique. Depending on the strength and aspect ratio of the initial perturbation, the response to the initial perturbation in the western sector can be dominated by inertia-gravity waves. The adjustment in the diabatic moist-convective shallow water model can be totally different and produces, depending on parameters, either Gill-like response or eastward-moving coherent dipolar structures of the type of equatorial modons, which do not appear in the “dry” adjustment, or vortices traveling, respectively, northwest in the Northern and southwest in the Southern hemispheres.
V. Zeitlin - One of the best experts on this subject based on the ideXlab platform.
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Geostrophic adjustment on the equatorial Beta-Plane revisited
Physics of Fluids, 2019Co-Authors: Masoud Rostami, V. ZeitlinAbstract:Abstract The process of geostrophic adjustment of localized large-scale pressure anomalies in the standard adiabatic shallow-water model on the equatorial Beta-Plane is revisited, and it is shown that the standard scenario of generation of westward-moving Rossby and eastward-moving Kelvin waves, which underlies the classical Gill theory of tropical circulation due to a localized heating, is not unique. Depending on the strength and aspect ratio of the initial perturbation, the response to the initial perturbation in the western sector can be dominated by inertia-gravity waves. The adjustment in the diabatic moist-convective shallow water model can be totally different and produces, depending on parameters, either Gill-like response or eastward-moving coherent dipolar structures of the type of equatorial modons, which do not appear in the “dry” adjustment, or vortices traveling, respectively, northwest in the Northern and southwest in the Southern hemispheres.
Vladimir Zeitlin - One of the best experts on this subject based on the ideXlab platform.
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Geostrophic adjustment on the equatorial Beta-Plane revisited
Physics of Fluids, 2019Co-Authors: Masoud Rostami, Vladimir ZeitlinAbstract:The process of geostrophic adjustment of localized large-scale pressure anomalies in the standard adiabatic shallow-water model on the equatorial Beta-Plane is revisited, and it is shown that the standard scenario of generation of westward-moving Rossby and eastward-moving Kelvin waves, which underlies the classical Gill theory of tropical circulation due to a localized heating, is not unique. Depending on the strength and aspect ratio of the initial perturbation, the response to the initial perturbation in the western sector can be dominated by inertia-gravity waves. The adjustment in the diabatic moist-convective shallow water model can be totally different and produces, depending on parameters, either Gill-like response or eastward-moving coherent dipolar structures of the type of equatorial modons, which do not appear in the “dry” adjustment, or vortices traveling, respectively, northwest in the Northern and southwest in the Southern hemispheres.The process of geostrophic adjustment of localized large-scale pressure anomalies in the standard adiabatic shallow-water model on the equatorial Beta-Plane is revisited, and it is shown that the standard scenario of generation of westward-moving Rossby and eastward-moving Kelvin waves, which underlies the classical Gill theory of tropical circulation due to a localized heating, is not unique. Depending on the strength and aspect ratio of the initial perturbation, the response to the initial perturbation in the western sector can be dominated by inertia-gravity waves. The adjustment in the diabatic moist-convective shallow water model can be totally different and produces, depending on parameters, either Gill-like response or eastward-moving coherent dipolar structures of the type of equatorial modons, which do not appear in the “dry” adjustment, or vortices traveling, respectively, northwest in the Northern and southwest in the Southern hemispheres.
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Hamilton's principle for quasigeostrophic motion
arXiv: Chaotic Dynamics, 1998Co-Authors: Darryl D. Holm, Vladimir ZeitlinAbstract:We show that the equation of quasigeostrophic (QG) potential vorticity conservation in geophysical fluid dynamics follows from Hamilton's principle for stationary variations of an action for geodesic motion in the f-plane case or its prolongation in the Beta-Plane case. This implies a new momentum equation and an associated Kelvin circulation theorem for QG motion. We treat the barotropic and two-layer baroclinic cases, as well as the continuously stratified case.
David Gurarie - One of the best experts on this subject based on the ideXlab platform.
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Scaling, spectra and zonal jets in Beta-Plane turbulence
Physics of Fluids, 2004Co-Authors: Sergey Danilov, David GurarieAbstract:A Beta-Plane approximation of the two-dimensional quasigeostrophic model describes a single layer (barotropic) fluid subjected to a latitudinally varying Coriolis parameter or topography. Rhines (1975) initiated the study of Beta-Plane turbulence. He predicted the inverse energy cascade into predominantly zonal modes, hence an array of eastward–westward jets, and estimated the jet number (celebrated Rhines scale). He also proposed a k−5 scaling law of zonal energy spectra. Our paper re-examines scaling, spectra, and zonal structure of Beta-Plane turbulence, based on theoretical predictions and numeric experiments. We show that the inverse cascade gives rise to strong organized zonal jets that evolve a peculiar frontal-band (“saw-tooth”) vorticity profile. Such structure affects all spectral properties of the system, by creating organized sequences of spectral peaks, and thus confounds any putative “scaling behavior.” The frontal-band structure appears consistently in all stochastically forced Beta-Plane f...
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Rhines scale and spectra of the Beta-Plane turbulence with bottom drag.
Physical review. E Statistical nonlinear and soft matter physics, 2002Co-Authors: Sergey Danilov, David GurarieAbstract:We study two-dimensional incompressible turbulence on the beta plane and propose a modification to the Rhines scale that takes into account the bottom friction. The modified Rhines scale is studied numerically, and found to predict accurately the jet number and the energy peak of the Beta-Plane turbulence for strong beta. The intermediate cases show a transition from the (isotropic) friction scale to the Rhines one, as the proper halting scale for the inverse cascade.
Paolo A. Paganetti - One of the best experts on this subject based on the ideXlab platform.
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Increased generation of alternatively cleaved β-amyloid peptides in cells expressing mutants of the amyloid precursor protein defective in endocytosis
Journal of neurochemistry, 2000Co-Authors: Renzo Cescato, Eric Dumermuth, Martin Spiess, Paolo A. PaganettiAbstract:The subcellular location of the secretases processing the beta-amyloid precursor protein (APP) is not established yet. We analyzed the generation of the beta-amyloid peptide (Abeta) in human embryonic kidney 293 cell lines stably expressing wild-type and noninternalizing mutants of human APP. APP lacking the entire cytoplasmic domain or with both tyrosine residues of the motif GYENPTY mutated to alanine showed at least fivefold reduced endocytosis. In these cell lines, the production of Abeta1-40 was substantially reduced, but accompanied by the appearance of two prominent alternative Abeta peptides differing at the amino-termini. Based on antibody reactivity and mobility in high- resolution gels in comparison with defined Abeta fragments, these peptides were identified as Abeta3-40 and Abeta5-40. Notably, these alternative Abeta peptides were not generated when the APP mutants were retained in the early secretory pathway by treatment with brefeldin A. These results indicate that the alternative processing is the result of APP accumulation at the plasma membrane and provide evidence of distinct beta-secretase activities. Cleavage amino-terminal to position 1 of Abeta occurs predominantly in endosomes, whereas the processing at positions 3 or 5 takes place at the plasma membrane.