Effects of Stratification on Shoaling Internal Tidal Bores

2021 ◽  
Author(s):  
Daniel P. Dauhajre ◽  
M. Jeroen Molemaker ◽  
James C. McWilliams ◽  
Delphine Hypolite
Keyword(s):  
Wave Amplitude ◽  
Vertical Structure ◽  
Internal Tide ◽  
Intermediate Zone ◽  
Local Flow ◽  
Large Wave ◽  
Tidal Bores ◽  
Wave Trains ◽  
Diagnostic Framework

AbstractIdealized simulations of a shoaling internal tide on a gently sloping, linear shelf provide a tool to investigate systematically the effects of stratification strength, vertical structure, and internal wave amplitude on internal tidal bores. Simulations that prescribe a range of uniform or variable stratifications and wave amplitudes demonstrate a variety of internal tidal bores characterized by shoreward propagating horizontal density fronts with associated overturning circulations. Qualitatively, we observe three classes of solution: 1) bores, 2) bores with trailing wave trains, and 3) no bores. Very strong stratification (small wave) or very weak stratification (large wave) inhibits bore formation. Bores exist in an intermediate zone of stratification strength and wave amplitude. Within this intermediate zone, wave trains can trail bores if the stratification is relatively weak or wave amplitude large. We observe three types of bore that arise dependent on the vertical structure of stratification and wave amplitude: 1) a ‘backward’ downwelling front (near uniform stratification, small to intermediate waves), 2) a ‘forward’ upwelling front (strong pycnocline, small to large waves), and 3) a ‘double’ bore with leading up and trailing downwelling front (intermediate pycnocline, intermediate to large waves). Visualization of local flow structures explores the evolution of each of these bore-types. A frontogenetic diagnostic framework elucidates the previously undiscussed, yet, universal role of vertical straining of a stratified fluid that initiates formation of bores. Bores with wave trains exhibit strong non-hydrostatic dynamics. The results of this study suggest that mid-to-outer shelf measurements of stratification and cross-shore flow can serve as proxies to indicate the class of bore further inshore.

scholarly journals A New Multiscale Model for the Madden–Julian Oscillation

2005 ◽  
Vol 62 (6) ◽  
pp. 1694-1721 ◽  
Author(s):  
Joseph A. Biello ◽  
Andrew J. Majda
Keyword(s):  
Vertical Structure ◽  
Multiscale Model ◽  
Structural Features ◽  
Synoptic Scale ◽  
Convective Envelope ◽  
Thermally Driven ◽  
Westerly Wind Burst ◽  
Wave Trains ◽  
Observational Record

Abstract A multiscale model of the MJO is developed here that accounts, in a simplified fashion, for both the upscale transfer from synoptic to planetary scales of momentum and temperature from wave trains of thermally driven equatorial synoptic-scale circulations in a moving convective envelope as well as direct mean heating on planetary scales. This model involves idealized thermally driven congestus synoptic-scale fluctuations in the eastern part of the moving wave envelope and convective superclusters in the western part of the envelope. The model self-consistently reproduces qualitatively many of the detailed structural features of the planetary circulation in the observations of the MJO, including the vertical structure in both the westerly onset region and the strong westerly wind burst region, as well as the horizontal quadrupole planetary vortex structure. The westerly midlevel inflow in the strong westerly region and the quadrupole vortex are largely produced in the model by the upscale transport of momentum to the planetary scales, while the midlevel easterly jet in the westerly onset region is substantially strengthened by this process. The role of wave trains of tilted organized synoptic-scale circulations is crucial for this fidelity with observations. The appeal of the multiscale models developed below is their firm mathematical underpinnings, simplicity, and analytic tractability while remaining self-consistent with many of the features of the observational record.

scholarly journals Nested Recharge Systems in Mountain Block Hydrology: High-Elevation Snowpack Generates Low-Elevation Overwinter Baseflow in a Rocky Mountain River

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2249
Author(s):  
Éowyn M. S. Campbell ◽  
M. Cathryn Ryan
Keyword(s):  
Rocky Mountain ◽  
High Elevation ◽  
Third Order ◽  
Relative Temperature ◽  
Local Flow ◽  
Fracture Systems ◽  
Lower Elevation ◽  
Flow Systems ◽  
Longitudinal Sampling

The majority of each year′s overwinter baseflow (i.e., winter streamflow) in a third-order eastern slopes tributary is generated from annual melting of high-elevation snowpack which is transmitted through carbonate and siliciclastic aquifers. The Little Elbow River and its tributaries drain a bedrock system formed by repeated thrust faults that express as the same siliciclastic and carbonate aquifers in repeating outcrops. Longitudinal sampling over an 18 km reach was conducted at the beginning of the overwinter baseflow season to assess streamflow provenance. Baseflow contributions from each of the two primary aquifer types were apportioned using sulfate, δ34SSO4, and silica concentrations, while δ18OH2O composition was used to evaluate relative temperature and/or elevation of the original precipitation. Baseflow in the upper reaches of the Little Elbow was generated from lower-elevation and/or warmer precipitation primarily stored in siliciclastic units. Counterintuitively, baseflow generated in the lower-elevation reaches originated from higher-elevation and/or colder precipitation stored in carbonate units. These findings illustrate the role of nested flow systems in mountain block recharge: higher-elevation snowmelt infiltrates through fracture systems in the cliff-forming—often higher-elevation—carbonates, moving to the lower-elevation valley through intermediate flow systems, while winter baseflow in local flow systems in the siliciclastic valleys reflects more influence from warmer precipitation. The relatively fast climatic warming of higher elevations may alter snowmelt timing, leaving winter water supply vulnerable to climatic change.

Intrathalline variability of some structural and physical parameters in the lichen genus Lasallia

1994 ◽  
Vol 72 (4) ◽  
pp. 415-428 ◽  
Author(s):  
F. Valladares ◽  
C. Ascaso ◽  
L. G. Sancho
Keyword(s):  
Chlorophyll Content ◽  
Marginal Zone ◽  
Central Zone ◽  
Intermediate Zone ◽  
Physical Parameters ◽  
Main Role ◽  
Active Growth ◽  
Lasallia Pustulata ◽  
Water Holding

The intrathalline variability of several physical and anatomical parameters of two lichens, Lasallia hispanica and Lasallia pustulata within the family Umbilicariaceae, was studied. In each thallus three zones or concentric rings were considered: the central zone, which includes the umbilicus, the intermediate zone, and the marginal zone. The study focussed on the thickness of the thallus and its layers, the increase of surface area and volume with hydration, the sample densities in dry and wet states, several stereological parameters (especially the volume and surface density of both symbionts related to each layer and to the thallus as a whole), and the chlorophyll content. Only slight differences were revealed between the two species, but significant intrathalline variation was observed. A marked decrease in the total chlorophyll content coincided with the thickening of the thallus from the periphery to the centre. The chlorophyll content of individual algal cells, however, presented an inverse gradient. The results suggest that the main role of the dense central zone would be as a water-holding zone while the active growth in the intermediate zone could counteract the continuous erosion of the marginal zone of these umbilicate lichens. Key words: Lasallia, intrathalline variability, mycobiont, photobiont, stereology, thallus density.

Governor-general and ruler of the viceroyalty in the system of the administrative and territorial structure of the Russian Empire in 1775–1796

2021 ◽  
pp. 151-157
Author(s):  
Ruslan N. Shutov
Keyword(s):  
Vertical Structure ◽  
Central Government ◽  
Main Type ◽  
Local Level ◽  
Executive Power ◽  
Division Of Powers ◽  
Russian State ◽  
Territorial Structure ◽  
The Russian Empire

The research is devoted to the study of the emergence and evolution of the institution of governorship. We consider the place and role, the specifics of the division of powers of the gover-nor-general and the ruler of the viceroyalty in the system of government of the Russian state in 1775–1796. Catherine II, from the beginning of her reign, made many efforts to strengthen the authority and power of the sovereign’s representative at local level – the governor. The governor-general and the governor were representatives of the central government and carried out its in-structions. In the newly created viceroyalties, the governor served as the direct ruler of the vice-royalty, and the role of the governor–general was to oversee the local administration and the com-munication between it and the central government. The inconsistency of the administrative and territorial reform led to the fact that one governor-general was appointed to several governorates, and the governor remained in each. The vertical structure of executive power built by Catherine II led to the high authority and quite successful activity of the governors. After becoming emperor, Paul I brought the reform carried out by Catherine II to its logical conclusion. During the reform of the governorate administration, the institution of the governor-general was abolished, and the governor became the main type of governor of the governorate.

scholarly journals Competing Fluid Forces Control Endothelial Sprouting in a 3-D Microfluidic Vessel Bifurcation Model

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 451 ◽  
Author(s):  
Ehsan Akbari ◽  
Griffin B. Spychalski ◽  
Kaushik K. Rangharajan ◽  
Shaurya Prakash ◽  
Jonathan W. Song
Keyword(s):  
Shear Stress ◽  
Fluid Flow ◽  
Bifurcation Point ◽  
Flow Dynamics ◽  
Laminar Shear Stress ◽  
Local Flow ◽  
Fluid Forces ◽  
Sprouting Angiogenesis ◽  
Laminar Shear

Sprouting angiogenesis—the infiltration and extension of endothelial cells from pre-existing blood vessels—helps orchestrate vascular growth and remodeling. It is now agreed that fluid forces, such as laminar shear stress due to unidirectional flow in straight vessel segments, are important regulators of angiogenesis. However, regulation of angiogenesis by the different flow dynamics that arise due to vessel branching, such as impinging flow stagnation at the base of a bifurcating vessel, are not well understood. Here we used a recently developed 3-D microfluidic model to investigate the role of the flow conditions that occur due to vessel bifurcations on endothelial sprouting. We observed that bifurcating fluid flow located at the vessel bifurcation point suppresses the formation of angiogenic sprouts. Similarly, laminar shear stress at a magnitude of ~3 dyn/cm2 applied in the branched vessels downstream of the bifurcation point, inhibited the formation of angiogenic sprouts. In contrast, co-application of ~1 µm/s average transvascular flow across the endothelial monolayer with laminar shear stress induced the formation of angiogenic sprouts. These results suggest that transvascular flow imparts a competing effect against bifurcating fluid flow and laminar shear stress in regulating endothelial sprouting. To our knowledge, these findings are the first report on the stabilizing role of bifurcating fluid flow on endothelial sprouting. These results also demonstrate the importance of local flow dynamics due to branched vessel geometry in determining the location of sprouting angiogenesis.

scholarly journals Psychopathological Symptoms and Gaming Motives in Disordered Gaming—A Psychometric Comparison between the WHO and APA Diagnostic Frameworks

2019 ◽  
Vol 8 (10) ◽  
pp. 1691 ◽  
Author(s):  
Christian Montag ◽  
Bruno Schivinski ◽  
Rayna Sariyska ◽  
Christopher Kannen ◽  
Zsolt Demetrovics ◽  
...  
Keyword(s):  
Online Survey ◽  
Attention Problems ◽  
World Health ◽  
Medical Attention ◽  
Gaming Disorder ◽  
Psychopathological Symptoms ◽  
Diagnostic Framework ◽  
Health Organization ◽  
Official Recognition

Background: ‘Gaming Disorder’ (GD) has received increased medical attention and official recognition from both the American Psychiatric Association (APA) and the World Health Organization (WHO). Although these two medical organizations have independently developed promising clinical diagnostic frameworks to assess disordered gaming, little is known about how these frameworks compare at different psychometric levels in terms of producing consistent outcomes in the assessment of GD. Methods: A sample of 1429 German gamers (Meanage = 29.74 years; SD = 12.37 years) completed an online survey including measures on different psychopathological symptoms (depression, loneliness and attention problems), gaming motives and disordered gaming according to the WHO and APA frameworks. Results: The findings suggest the existence of minor discrepancies in the estimation of prevalence rates of GD according among the two frameworks. Nevertheless, both diagnostic frameworks are fairly consistent in the psychometric prediction of GD in relation to gaming motives and psychopathological symptoms. The findings underscore the role of key gaming motives as risk factors and protective factors across both diagnostic frameworks. Finally, the study provides support for the WHO diagnostic framework for GD and its measurement with the German Gaming Disorder Test (GDT). The findings and their implications are further discussed in terms of clinical relevance.

Role of vertical structure of cloud microphysical properties on cloud radiative forcing over the Asian monsoon region

2015 ◽  
Vol 45 (11-12) ◽  
pp. 3331-3345 ◽  
Author(s):  
V. Ravi Kiran ◽  
M. Rajeevan ◽  
H. Gadhavi ◽  
S. Vijaya Bhaskara Rao ◽  
A. Jayaraman
Keyword(s):  
Radiative Forcing ◽  
Vertical Structure ◽  
Asian Monsoon ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Cloud Radiative Forcing ◽  
Microphysical Properties

scholarly journals Caught between nationalism and transnationalism: How Central and East European states respond to East–West emigration

2018 ◽  
Vol 39 (3) ◽  
pp. 338-352 ◽  
Author(s):  
Myra A Waterbury
Keyword(s):  
State Policies ◽  
Eastern European ◽  
Large Wave ◽  
East European ◽  
Policy Responses ◽  
Different Types ◽  
Transnational Engagement ◽  
East West

This article seeks to explain the varied policy responses to the large wave of emigration from Central and Eastern European states during the last two decades, focusing on the cases of Hungary, Bulgaria, Romania, and Poland. Differing degrees of emigrant engagement by these states are explained by the role of internal minorities as active members of the emigrant population and the overall political and demographic relevance of historical kin. This study contributes to our understanding of what shapes state policies towards different types of external populations. It also highlights the particular challenges of state-led transnational engagement in a supranational border regime.

Shear Cavitation

2005 ◽  
Author(s):  
P. A. Kottke ◽  
S. Bair ◽  
W. O. Winer
Keyword(s):  
Normal Stress ◽  
Hydrodynamic Pressure ◽  
Local Flow ◽  
Flowing Liquid ◽  
Principal Normal Stress ◽  
State Of Stress ◽  
Nucleation Sites ◽  
Theoretical Foundations ◽  
Viscous Stresses

The importance of cavitation in lubrication hydrodynamics is well recognized. Cavitation can also act as a source of experimental error in rheological measurements. Therefore, the ability to understand and predict cavitation is important for tribology. Nearly all models for cavitation prediction are based on the local hydrodynamic pressure. The appropriateness of this approach when viscous stresses are of the order of the hydrodynamic pressure is questionable. One cavitation model that considers the state of stress in a flowing liquid is the principal normal stress cavitation criterion (PNSCC), which proposes that cavitation will occur when the most tensile principal normal stress exceeds some critical value. Although this hypothesis can accommodate many experimental observations, its theoretical foundations are weak. In particular, it fails to account for the tensile strength of liquids and resulting need for nucleation sites; it neglects the role of transport of dissolved gases; and it does not consider the effect of a growing bubble on the local flow, and hence local state of stress. We demonstrate cavitation in low Reynolds number Couette flow, and present a model for cavitation in shear in the limit of creeping (Stokes) flow, which corrects for the theoretical failures of the PNSCC. We use numerical simulation to analyze cavitation onset, and obtain a more general cavitation criteria from which the PNSCC is recovered under certain conditions.

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