The role of advection and density gradients in driving the residual circulation along a macrotidal and convergent estuary with non-idealized geometry

The stratospheric transport circulation, or Brewer-Dobson Circulation (BDC), is often conceptually seperated into advection along the residual circulation and two-way mixing. In particular the latter part has recently been found to exert a strong influence on inter-model differences of mean age of Air (AoA), a common measure of the BDC. However, the precise reason for model differences in two-way mixing remains unknown, as many model components in multi-model projects differ. One component that likely plays an important role is model resolution, both vertically and horizontally. To analyse this aspect, we carried out a set of simulations with identical and constant year 2000 climate forcing varying the spectral horizontal resolution (T31,T42,T63,T85) and the number of vertical levels (L31,L47,L90). We find that increasing the vertical resolution leads to an increase in mean AoA. Most of this change can be attributed to aging by mixing. The mixing efficiency, defined as the ratio of isentropic mixing strength and the diabatic circulation, shows the same dependency on vertical resolution. While horizontal resolution changes do not systematically change mean AoA, we do find a systematic decrease in the mixing efficiency with increasing horizontal resolution. Non-systematic changes in the residual circulation partly compensate the mixing efficiency changes, leading to the non-systematic mean AoA changes. The mixing efficiency changes with vertical and horizontal resolution are consistent with expectations on the effects of numerical dispersion on mean AoA. To further investigate the most relevant regions of mixing differences, we analyse height-resolved mixing efficiency differences. Overall, this work will help to shed light on the underlying reasons for the large biases of climate models in simulating stratospheric transport.

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Thermospheric Meridional Wind Control on Equatorial Scintillations and the Role of the Evening F-Region Height Rise, E × B Drift Velocities and F2-Peak Density Gradients

Surveys in Geophysics ◽

10.1007/s10712-010-9101-3 ◽

2010 ◽

Vol 31 (5) ◽

pp. 509-530 ◽

Cited By ~ 14

Author(s):

M. T. A. H. Muella ◽

E. R. de Paula ◽

P. R. Fagundes ◽

J. A. Bittencourt ◽

Y. Sahai

Keyword(s):

Meridional Wind ◽

Density Gradients ◽

Peak Density ◽

F Region

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Pattern formation of vascular smooth muscle cells subject to nonuniform fluid shear stress: role of PDGF-β receptor and Src

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00434.2003 ◽

2003 ◽

Vol 285 (3) ◽

pp. H1081-H1090 ◽

Cited By ~ 11

Author(s):

Shu Q. Liu ◽

Christopher Tieche ◽

Dalin Tang ◽

Paul Alkema

Keyword(s):

Shear Stress ◽

Smooth Muscle ◽

Cell Density ◽

Fluid Shear Stress ◽

Density Gradients ◽

Dependent Manner ◽

Fluid Shear ◽

Polymer Implants ◽

Β Receptor

Blood vessels are subject to fluid shear stress, a hemodynamic factor that inhibits the mitogenic activities of vascular cells. The presence of nonuniform shear stress has been shown to exert graded suppression of cell proliferation and induces the formation of cell density gradients, which in turn regulate the direction of smooth muscle cell (SMC) migration and alignment. Here, we investigated the role of platelet-derived growth factor (PDGF)-β receptor and Src in the regulation of such processes. In experimental models with vascular polymer implants, SMCs migrated from the vessel media into the neointima of the implant under defined fluid shear stress. In a nonuniform shear model, blood shear stress suppressed the expression of PDGF-β receptor and the phosphorylation of Src in a shear level-dependent manner, resulting in the formation of mitogen gradients, which were consistent with the gradient of cell density as well as the alignment of SMCs. In contrast, uniform shear stress in a control model elicited an even influence on the activity of mitogenic molecules without modulating the uniformity of cell density and did not significantly influence the direction of SMC alignment. The suppression of the PDGF-β receptor tyrosine kinase and Src with pharmacological substances diminished the gradients of mitogens and cell density and reduced the influence of nonuniform shear stress on SMC alignment. These observations suggest that PDGF-β receptor and Src possibly serve as mediating factors in nonuniform shear-induced formation of cell density gradients and alignment of SMCs in the neointima of vascular polymer implants.

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On the Control of the Residual Circulation and Stratospheric Temperatures in the Arctic by Planetary Wave Coupling

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-13-0138.1 ◽

2013 ◽

Vol 71 (1) ◽

pp. 195-206 ◽

Cited By ~ 19

Author(s):

Tiffany A. Shaw ◽

Judith Perlwitz

Keyword(s):

Heat Flux ◽

The Arctic ◽

Dynamical Regime ◽

Negative Events ◽

Residual Circulation ◽

Dynamical Processes ◽

Diabatic Processes ◽

New Interpretation ◽

The Impact

Abstract It is well established that interannual variability of eddy (meridional) heat flux near the tropopause controls the variability of Arctic lower-stratospheric temperatures during spring via a modification of the strength of the residual circulation. While most studies focus on the role of anomalous heat flux values, here the impact of total (climatology plus anomaly) negative heat flux events on the Arctic stratosphere is investigated. Utilizing the Interim ECMWF Re-Analysis (ERA-Interim) dataset, it is found that total negative heat flux events coincide with a transient reversal of the residual circulation and cooling of the Arctic lower stratosphere. The negative events weaken the seasonally averaged adiabatic warming. The analysis provides a new interpretation of the winters of 1997 and 2011, which are known to have the lowest March Arctic lower-stratospheric temperatures in the satellite era. While most winters involve positive and negative heat flux extremes, the winters of 1997 and 2011 are unique in that they only involved extreme negative events. This behavior contributed to the weakest adiabatic downwelling in the satellite era and suggests a dynamical contribution to the extremely low temperatures during those winters that could not be accounted for by diabatic processes alone. While it is well established that dynamical processes contribute to the occurrence of stratospheric sudden warming events via extreme positive heat flux events, the results show that dynamical processes also contribute to cold winters with subsequent impact on Arctic ozone loss. The results highlight the importance of interpreting stratospheric temperatures in the Arctic in the context of the dynamical regime with which they are associated.

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Tidal asymmetry in the Sylt-Romo Bight, south-eastern North Sea

10.5194/egusphere-egu2020-1359 ◽

2020 ◽

Author(s):

Vera Fofonova ◽

Alexey Androsov ◽

Lasse Sander ◽

Ivan Kuznetsov ◽

Felipe Amorim ◽

...

Keyword(s):

Circulation Pattern ◽

Tidal Energy ◽

Tidal Asymmetry ◽

Residual Circulation ◽

Linear Processes ◽

Bathymetric Data ◽

Full Analysis ◽

Bathymetric Map

&#160;The study is dedicated to the tidal dynamics in the Sylt-R&#248;m&#248; Bight with a focus on the non-linear processes. The FESOM-C model was used as the numerical tool, which works with triangular, rectangular or mixed grids and is equipped with a wetting/drying option. As the model&#8217;s success at resolving currents largely depends on the quality of the bathymetric data, we have created a new bathymetric map for an area based on recent studies of Lister Deep, Lister Ley, and the H&#248;jer and R&#248;m&#248; Deep areas. This new bathymetric product made it feasible to work with high resolution grids (up to 2 m in the wetting/drying zone). As a result, we were able to study the tidal energy transformation and the role of higher harmonics in the domain in detail. The tidal ellipses, maximum tidally-induced velocities, energy fluxes and residual circulation maps were constructed and analysed for the entire bight. Additionally, tidal asymmetry maps were introduced and constructed. The full analysis was performed on two grids with different structures and showed a convergence of the results as well as fulfillment of the energy balance. The tidal residual circulation and asymmetric tidal cycles largely define the circulation pattern, transport and accumulation of sediment and the distribution of bedforms in the bight, therefore the results are necessary and useful benchmarks for further studies in the area, including baroclinic and sediment dynamics investigations.

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On the role of vertical electron density gradients in the generation of type II irregularities associated with blanketing ES(ESb) during counter equatorial electrojet events: A case study

Radio Science ◽

10.1029/2002rs002725 ◽

2004 ◽

Vol 39 (3) ◽

pp. n/a-n/a ◽

Cited By ~ 8

Author(s):

C. V. Devasia ◽

N. Jyoti ◽

K. S. V. Subbarao ◽

Diwakar Tiwari ◽

C. Raghava Reddi ◽

...

Keyword(s):

Electron Density ◽

Equatorial Electrojet ◽

Density Gradients ◽

Type Ii

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The role of wind-forcing in the distribution of larval fish in Galway Bay, Ireland

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315412001348 ◽

2012 ◽

Vol 93 (2) ◽

pp. 471-478 ◽

Cited By ~ 7

Author(s):

Stephen Comerford ◽

Deirdre Brophy

Keyword(s):

Environmental Factors ◽

Generalized Linear Model ◽

Larval Fish ◽

Juvenile Fish ◽

Residual Circulation ◽

Tidal State ◽

Merlangius Merlangus ◽

Sampling Season ◽

Distribution Of Fish

The ichthyoplankton of Galway Bay was sampled over the spring and summer of 2007 and 2008 to determine what environmental factors influenced the distribution of larval and early juvenile fish. A total of 549 fish representing 27 taxa were caught. Catches decreased throughout each sampling season, and were generally poor in 2007. Catches were numerically dominated by sprat (Sprattus sprattus), dab (Limanda limanda), sand eel (Hyperoplus immaculatus) and whiting (Merlangius merlangus). Environmental factors driving distribution of fish were modelled using a binomial generalized linear model. The strength and direction of wind in the five days preceding sampling was the only significant environmental factor. Sustained onshore winds increased the probability of encountering larval fish in the areas sampled. The rainfall, tidal state, tow depth and wind conditions during sampling were not significant. Among the parameters measured it appears that onshore winds sufficiently strong to overcome the residual circulation are the main physical driver for the distribution of larval fish in Galway Bay.

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The role of the winter residual circulation in the summer mesopause regions in WACCM

10.5194/acp-2017-647 ◽

2017 ◽

Author(s):

Maartje Sanne Kuilman ◽

Bodil Karlsson

Keyword(s):

Gravity Waves ◽

General Circulation ◽

Climate Model ◽

Temperature Response ◽

Circulation Model ◽

Coupling Mechanism ◽

Residual Circulation ◽

Mesospheric Temperature ◽

Temperature Signal

Abstract. High winter planetary wave activity warms the summer polar mesopause via a link between the two hemispheres. In a recent study carried out with the Kühlungsborn Mechanistic general Circulation Model (KMCM), it was shown that the net effect of this interhemispheric coupling mechanism is a cooling of the summer polar mesospheres and that this temperature response is tied to the strength of the gravity wave-driven winter mesospheric flow. We here reconfirm the hypothesis that the summer polar mesosphere would be substantially warmer without the circulation in the winter mesosphere, using the widely-used Whole Atmosphere Community Climate Model (WACCM). In addition, the role of the stratosphere in shaping the conditions of the summer polar mesosphere is investigated. Using composite analysis, we show that if winter gravity waves are absent, a weak stratospheric Brewer-Dobson circulation would lead to a warming of the summer mesosphere region instead of a cooling, and vice versa. This is opposing the temperature signal of the interhemispheric coupling in the mesosphere, in which a cold winter stratosphere goes together with a cold summer mesopause. We hereby strengthen the evidence that the equatorial mesospheric temperature response, driven by the winter gravity waves, is a crucial step in the interhemispheric coupling mechanism.

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Role of density gradients on miscible Rayleigh–Taylor fingers in porous media

AIP Advances ◽

10.1063/5.0054224 ◽

2021 ◽

Vol 11 (8) ◽

pp. 085201

Author(s):

Satyajit Pramanik ◽

Manoranjan Mishra

Keyword(s):

Porous Media ◽

Density Gradients

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