scholarly journals Potential Vorticity Constraint on the Flow between Two Basins

2007 ◽  
Vol 37 (9) ◽  
pp. 2251-2266 ◽  
Author(s):  
Jiayan Yang ◽  
James F. Price
Keyword(s):  
Potential Vorticity ◽  
Large Scale ◽  
Circulation Pattern ◽  
Viscous Drag ◽  
Frictional Torque ◽  
Boundary Current ◽  
Coriolis Parameter ◽  
Basin Scale ◽  
Straightforward Consequence

Abstract This paper examines the role of potential vorticity (PV) balance in source- and sink-driven flows between two basins. As shown in previous studies, PV advection into a basin, say a positive PV advection, requires a negative frictional torque to maintain a steady PV balance. This sense of torque may be provided by a cyclonic boundary current within the basin. The PV advection through a channel is due almost entirely to advection of planetary PV, f/H, where f is the Coriolis parameter and H is the column thickness. Therefore a localized change of depth, and thus H in the channel, directly affects the PV transport and will result in a basinwide change of the circulation pattern. For example, if the channel depth is made shallower while holding the transport fixed, the PV advection is then increased and the result may be a strong recirculation within the basin, as much as two orders of magnitude greater than the transport through the channel. When the basins are connected by two channels at different latitudes or with different sill depths, the throughflow is found to be divided between the two channels in a way that satisfies the integral constraint for flow around an island. The partition of the flow between two channels appears to be such as to minimize the net frictional torque. In still another set of experiments, the large-scale pressure difference (layer thickness) between the basins is specified and held fixed, while the throughflow is allowed to vary in response to changes in the frictional torque. The interbasin transport is strongly influenced by the length of the boundary or the magnitude of the viscosity in the sense that a greater PV frictional torque allows a greater PV transport and vice versa. This result is counterintuitive, if it is assumed that the throughflow is determined by viscous drag within the channel but is a straightforward consequence of the basin-scale PV balance. Thus, the important frictional effect in these experiments is on the basin-scale flow and not on the channel scale.

scholarly journals Western Arctic Shelfbreak Eddies: Formation and Transport

2008 ◽  
Vol 38 (8) ◽  
pp. 1644-1668 ◽  
Author(s):  
Michael A. Spall ◽  
Robert S. Pickart ◽  
Paula S. Fratantoni ◽  
Albert J. Plueddemann
Keyword(s):  
Numerical Model ◽  
Potential Vorticity ◽  
Chukchi Sea ◽  
Baroclinic Instability ◽  
Relative Vorticity ◽  
Time Dependent ◽  
Shelf Water ◽  
Boundary Current ◽  
Basin Scale ◽  
Western Arctic

Abstract The mean structure and time-dependent behavior of the shelfbreak jet along the southern Beaufort Sea, and its ability to transport properties into the basin interior via eddies are explored using high-resolution mooring data and an idealized numerical model. The analysis focuses on springtime, when weakly stratified winter-transformed Pacific water is being advected out of the Chukchi Sea. When winds are weak, the observed jet is bottom trapped with a low potential vorticity core and has maximum mean velocities of O(25 cm s−1) and an eastward transport of 0.42 Sv (1 Sv ≡ 106 m3 s−1). Despite the absence of winds, the current is highly time dependent, with relative vorticity and twisting vorticity often important components of the Ertel potential vorticity. An idealized primitive equation model forced by dense, weakly stratified waters flowing off a shelf produces a mean middepth boundary current similar in structure to that observed at the mooring site. The model boundary current is also highly variable, and produces numerous strong, small anticyclonic eddies that transport the shelf water into the basin interior. Analysis of the energy conversion terms in both the mooring data and the numerical model indicates that the eddies are formed via baroclinic instability of the boundary current. The structure of the eddies in the basin interior compares well with observations from drifting ice platforms. The results suggest that eddies shed from the shelfbreak jet contribute significantly to the offshore flux of heat, salt, and other properties, and are likely important for the ventilation of the halocline in the western Arctic Ocean. Interaction with an anticyclonic basin-scale circulation, meant to represent the Beaufort gyre, enhances the offshore transport of shelf water and results in a loss of mass transport from the shelfbreak jet.

scholarly journals Storylines of the 2018 Northern Hemisphere heat wave at pre-industrial and higher global warming levels

2020 ◽  
Author(s):  
Kathrin Wehrli ◽  
Mathias Hauser ◽  
Sonia I. Seneviratne
Keyword(s):  
Global Warming ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Heat Waves ◽  
Circulation Pattern ◽  
Community Earth System Model ◽  
Anomalous Atmospheric Circulation ◽  
Simultaneous Heat ◽  
Different Levels

<p>The 2018 summer was unusually hot in large areas of the Northern Hemisphere and simultaneous heat waves on three continents led to major impacts to agriculture and society. The event was driven by the anomalous atmospheric circulation pattern during that summer and it was only possible in a climate with global warming. There are indications that in a future, warmer climate similar events might occur regularly, affecting major ‘breadbasket’ regions of the Northern Hemisphere.</p><p>This study aims to understand the role of climate change for driving the intensity of the 2018 summer and to explore the sensitivity to changing warming levels. Model simulations are performed using the Community Earth System Model to investigate storylines for the extreme 2018 summer given the observed atmospheric large-scale circulation but different levels of background global warming: no human imprint, the 2018 conditions, and different mean global warming levels (1.5°C, 2°C, 3°C, and 4°C). The storylines explore the consequences of the event in an alternative warmer or colder world and thus help to increase our understanding of the drivers involved. The results reveal a strong contribution by the present-day level of global warming and provide an outlook to similar events in a possible future climate.</p>

scholarly journals The Role of Eddies in Buoyancy-Driven Eastern Boundary Currents

2018 ◽  
Vol 48 (12) ◽  
pp. 2829-2850 ◽  
Author(s):  
Suyash Bire ◽  
Christopher L. P. Wolfe
Keyword(s):  
Large Scale ◽  
Weighted Average ◽  
Boundary Current ◽  
Form Drag ◽  
Boundary Currents ◽  
Warm Core ◽  
Eastern Boundary ◽  
Eastern Boundary Currents ◽  
Cold Core

AbstractAn eastern boundary current (EBC) system driven by a large-scale meridional buoyancy gradient is simulated using an idealized eddy-resolving model. The EBC system consists of a pair of stacked meridional currents that flow poleward near the surface and equatorward at intermediate depths. Buoyancy advection in the EBC is primarily balanced by the shedding of eddies, with anticyclonic, warm-core eddies dominating near the surface and cyclonic, cold-core eddies found at intermediate depths. These boundary eddies play a significant role in both the eastern boundary circulation—by helping to trap the EBC near the coast—and the large-scale circulation through their effect on the downwelling limb of the overturning circulation. Momentum and thickness budgets analyzed using the thickness-weighted average framework highlight the role of eddy form drag in shaping and maintaining the EBC. The efficiency of the form drag increases dramatically at the offshore flank of the EBC. This zonal variation of the form drag is essential for maintaining a swift, narrow EBC. The essential physics of the EBC are illustrated using a simple, semianalytical model.

Adiabatic Eastern Boundary Currents

2013 ◽  
Vol 43 (6) ◽  
pp. 1127-1149 ◽  
Author(s):  
Paola Cessi ◽  
Christopher L. Wolfe
Keyword(s):  
Potential Vorticity ◽  
Relative Vorticity ◽  
Oceanic Circulation ◽  
Boundary Current ◽  
Coriolis Parameter ◽  
Mean Velocity ◽  
Eastern Boundary ◽  
Eastern Boundary Current ◽  
Eddy Fluxes ◽  
The Mean

Abstract The dynamics of the eastern boundary current of a high-resolution, idealized model of oceanic circulation are analyzed and interpreted in terms of residual mean theory. In this framework, it is clear that the eastern boundary current is adiabatic and inviscid. Nevertheless, the time-averaged potential vorticity is not conserved along averaged streamlines because of the divergence of Eliassen–Palm fluxes, associated with buoyancy and momentum eddy fluxes. In particular, eddy fluxes of buoyancy completely cancel the mean downwelling or upwelling, so that there is no net diapycnal residual transport. The eddy momentum flux acts like a drag on the mean velocity, opposing the acceleration from the eddy buoyancy flux: in the potential vorticity budget this results in a balance between the divergences of eddy relative vorticity and buoyancy fluxes, which leads to a baroclinic eastern boundary current whose horizontal scale is the Rossby deformation radius and whose vertical extent depends on the eddy buoyancy transport, the Coriolis parameter, and the mean surface buoyancy distribution.

scholarly journals On the role of thermal expansion and compression in large scale atmospheric energy and mass transports

2018 ◽  
Author(s):  
Melville E. Nicholls ◽  
Roger A. Pielke Sr.
Keyword(s):  
Thermal Expansion ◽  
Heat Source ◽  
Total Energy ◽  
Speed Of Sound ◽  
Large Scale ◽  
Energy Transport ◽  
Implicit Time ◽  
Coriolis Parameter ◽  
Compression Waves

Abstract. There are currently two views of how atmospheric total energy transport is accomplished. One view considers total energy as a quantity that is transported in an advective-like manner by the wind. The other considers that thermal expansion and the resultant compression of the surrounding air causes a transport of total energy in a wave-like manner at the speed of sound. This latter view emerged as the result of detailed analysis of fully compressible mesoscale model simulations that demonstrated considerable transfer of internal and gravitational potential energy at the speed of sound by Lamb waves. In this study, results are presented of idealized experiments with a fully compressible model designed to examine the large-scale transfers of total energy and mass when local heat sources are prescribed. For simplicity a Cartesian grid was used, there was a horizontally homogeneous basic state, and the simulations did not include moisture. Three main experimental designs were employed: The first has a convective storm scale heat source. This experiment illustrates the basic process of expansion in the heated region leading to compression of the adjacent air and the subsequent formation of a Lamb wave that propagates laterally at the speed of sound. The second experiment has a continent scale heat source prescribed near the surface to represent surface heating and which includes a constant Coriolis parameter. Results indicate that after several hours considerable amounts of total energy and mass are transferred offshore at the speed of sound. This simulation is compared to one with the term in the governing equations responsible for forcing thermal compression waves omitted. There is a fairly small but nevertheless significant difference of the wind field compared to the fully compressible results. A comparison of the fully compressible simulation with a simulation without the Coriolis force illustrates the role of geostrophic adjustment in significantly influencing the total energy distribution. The third experiment has a cloud cluster scale heat source prescribed at the equator and which includes a latitude dependent Coriolis parameter. Results show considerable amounts of meridional total energy and mass transfer at the speed of the sound. This study suggests that the current understanding of large scale total energy transfer that assumes it is accomplished solely in an advective-like manner by the winds is not correct. If so the current theory would be incomplete, and since some of the transfer might be occurring at the speed of sound this could bring into question the methodology commonly used to attribute the total energy transports to transient eddy, stationary eddy, and mean meridional circulations. Based on these results the conceptual differences between the terms total energy transport and heat transport in a fluid are discussed. Fast moving compression waves are unlikely to be accurately simulated by most climate models since they utilize semi-implicit time differencing techniques, and this could potentially be a source of error that has yet to be evaluated.

Convection in a rotating cavity: modelling ocean circulation

1989 ◽  
Vol 207 ◽  
pp. 453-474 ◽  
Author(s):  
Scott A. Condie ◽  
Ross W. Griffiths
Keyword(s):  
Ocean Circulation ◽  
Potential Vorticity ◽  
Large Scale ◽  
Initial Boundary ◽  
Vertical Axis ◽  
Temperature Fields ◽  
Laboratory Model ◽  
Boundary Currents ◽  
Heating And Cooling ◽  
Basin Scale

Large-scale oceanic flows, ranging from large estuaries to basin-scale abyssal circulation, can be driven by imposed lateral density gradients and are significantly influenced by the Earth's rotation. Some essential features of such flows have been incorporated into a laboratory model by differentially heating and cooling the vertical endwalls of a shallow rectangular cavity, rotating about a vertical axis through its centre. In this paper, the flow observed after this system had been allowed to develop to a steady mean state is described. Measurements were made of the velocity and temperature fields, as well as the variability in temperature field associated with eddy motions. The temperature data were also used to calculate the potential vorticity distribution within the cavity. These results indicate that the heated and cooled end-walls acted not only as continuous sources of buoyancy, but also of anomalous potential vorticity. It is shown that the potential vorticity served as an indicator and tracer of the laboratory flow. The structure and location of boundary currents were largely determined by nonlinear potential vorticity dynamics which resulted in a mean circulation consisting of two basin-scale counter-rotating gyres. This flow differed markedly from the initial boundary currents set up by Kelvin waves.

scholarly journals Regional imprints of changes in the Atlantic Meridional Overturning Circulation in the eddy-rich ocean model VIKING20X

Ocean Science ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1177-1211
Author(s):  
Arne Biastoch ◽  
Franziska U. Schwarzkopf ◽  
Klaus Getzlaff ◽  
Siren Rühs ◽  
Torge Martin ◽  
...  
Keyword(s):  
Large Scale ◽  
Temporal Evolution ◽  
Dominant Role ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Western Boundary ◽  
Boundary Current ◽  
Overturning Circulation ◽  
Basin Scale ◽  
Meridional Overturning

Abstract. A hierarchy of global 1/4∘ (ORCA025) and Atlantic Ocean 1/20∘ nested (VIKING20X) ocean–sea-ice models is described. It is shown that the eddy-rich configurations performed in hindcasts of the past 50–60 years under CORE and JRA55-do atmospheric forcings realistically simulate the large-scale horizontal circulation, the distribution of the mesoscale, overflow and convective processes, and the representation of regional current systems in the North and South Atlantic. The representation of the Atlantic Meridional Overturning Circulation (AMOC), and in particular the long-term temporal evolution, strongly depends on numerical choices for the application of freshwater fluxes. The interannual variability of the AMOC instead is highly correlated among the model experiments and also with observations, including the 2010 minimum observed by RAPID at 26.5∘ N. This points to a dominant role of the wind forcing. The ability of the model to represent regional observations in western boundary current (WBC) systems at 53∘ N, 26.5∘ N and 11∘ S is explored. The question is investigated of whether WBC systems are able to represent the AMOC, and in particular whether these WBC systems exhibit similar temporal evolution to that of the zonally integrated AMOC. Apart from the basin-scale measurements at 26.5∘ N, it is shown that in particular the outflow of North Atlantic Deepwater at 53∘ N is a good indicator of the subpolar AMOC trend during the recent decades, once provided in density coordinates. The good reproduction of observed AMOC and WBC trends in the most reasonable simulations indicate that the eddy-rich VIKING20X is capable of representing realistic forcing-related and ocean-intrinsic trends.

The Role of Sense of Direction and Other Factors During Navigation in a Large-Scale, Unconstrained Environment

2013 ◽  
Author(s):  
Elisabeth J. Ploran ◽  
Ericka Rovira ◽  
James C. Thompson ◽  
Raja Parasuraman
Keyword(s):  
Large Scale ◽  
Sense Of Direction

Magnetic Properties of xCeO2•(50 − x) PbO•50B2O3 Glasses and Glass Ceramics

2017 ◽  
Vol 13 (1) ◽  
pp. 4486-4494 ◽  
Author(s):  
G.El Damrawi ◽  
F. Gharghar
Keyword(s):  
Magnetic Properties ◽  
Large Scale ◽  
Glass Ceramics ◽  
Magnetic Behavior ◽  
Crystal Formation ◽  
Dual Roles ◽  
Effective Agent ◽  
Ordered Structures ◽  
Essential Change

Cerium oxide in borate glasses of composition xCeO2·(50 − x)PbO·50B2O3 plays an important role in changing both microstructure and magnetic behaviors of the system. The structural role of CeO2 as an effective agent for cluster and crystal formation in borate network is clearly evidenced by XRD technique. Both structure and size of well-formed cerium separated clusters have an effective influence on the structural properties. The cluster aggregations are documented to be found in different range ordered structures, intermediate and long range orders are the most structures in which cerium phases are involved. The nano-sized crystallized cerium species in lead borate phase are evidenced to have magnetic behavior.  The criteria of building new specific borate phase enriched with cerium as ferrimagnetism has been found to keep the magnetization in large scale even at extremely high temperature. Treating the glass thermally or exposing it to an effective dose of ionized radiation is evidenced to have an essential change in magnetic properties. Thermal heat treatment for some of investigated materials is observed to play dual roles in the glass matrix. It can not only enhance alignment processes of the magnetic moment but also increases the capacity of the crystallite species in the magnetic phases. On the other hand, reverse processes are remarked under the effect of irradiation. The magnetization was found to be lowered, since several types of the trap centers which are regarded as defective states can be produced by effect of ionized radiation. 

The Impact of Quantitative Easing on Emerging Markets – Literature Review

e-Finanse ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 67-76
Author(s):  
Piotr Bartkiewicz
Keyword(s):  
Emerging Markets ◽  
Large Scale ◽  
Empirical Literature ◽  
Quantitative Easing ◽  
Methodological Choices ◽  
The Subject ◽  
Methodological Approaches ◽  
The Impact ◽  
Sufficient Precision

AbstractThe article presents the results of the review of the empirical literature regarding the impact of quantitative easing (QE) on emerging markets (EMs). The subject is of interest to policymakers and researchers due to the increasingly larger role of EMs in the world economy and the large-scale capital flows occurring after 2009. The review is conducted in a systematic manner and takes into consideration different methodological choices, samples and measurement issues. The paper puts the summarized results in the context of transmission channels identified in the literature. There are few distinct methodological approaches present in the literature. While there is a consensus regarding the direction of the impact of QE on EMs, its size and durability have not yet been assessed with sufficient precision. In addition, there are clear gaps in the empirical findings, not least related to relative underrepresentation of the CEE region (in particular, Poland).

Sign in / Sign up

Export Citation Format

Share Document