A coastal upwelling circulation model with eddy viscosity depending on Richardson number

1981 ◽  
pp. 203-208 ◽  
Author(s):  
Masahiro Endoh ◽  
Christopher N. K. Mooers ◽  
Walter R. Johnson
Keyword(s):  
Richardson Number ◽  
Eddy Viscosity ◽  
Coastal Upwelling ◽  
Circulation Model

Assessing the performance of a multi-nested ocean circulation model using satellite remote sensing and in situ observations

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Shiliang Shan ◽  
Jinyu Sheng ◽  
Kyoko Ohashi ◽  
Mathieu Dever
Keyword(s):  
Remote Sensing ◽  
Nova Scotia ◽  
Ocean Circulation ◽  
Satellite Remote Sensing ◽  
Coastal Upwelling ◽  
Circulation Model ◽  
Tidal Mixing ◽  
Scotian Shelf ◽  
Ocean Circulation Model

This study presents a multi-nested ocean circulation model developed recently for the central Scotian Shelf. The model consists of four submodels downscaling from the eastern Canadian Shelf to the central Scotian Shelf. The model is driven by tides, river discharges, and atmospheric forcing. The model results are validated against observations, including satellite remote sensing data from GHRSST and Aquarius and in situ measurements taken by tide gauges, a marine buoy, ADCPs and CTDs. The ocean circulation model is able to capture variations of sea level, hydrography and the Nova Scotia Current on timescales of days to seasons over the central Scotian Shelf. Model results are used in a process study to examine the effect of tidal mixing and wind-driven coastal upwelling in the formation of cold surface waters along the coast of Nova Scotia.

scholarly journals Quantifying the Contributions of Tidal Straining and Gravitational Circulation to Residual Circulation in Periodically Stratified Tidal Estuaries

2010 ◽  
Vol 40 (6) ◽  
pp. 1243-1262 ◽  
Author(s):  
Hans Burchard ◽  
Robert D. Hetland
Keyword(s):  
Water Column ◽  
Strouhal Number ◽  
Richardson Number ◽  
Eddy Viscosity ◽  
Estuarine Circulation ◽  
Turbulence Closure ◽  
Closure Model ◽  
Tidal Straining ◽  
Gravitational Circulation ◽  
Turbulence Closure Model

Abstract This numerical modeling study quantifies for the first time the contribution of various processes to estuarine circulation in periodically stratified tidal flow under the impact of a constant horizontal buoyancy gradient. The one-dimensional water column equations with periodic forcing are first cast into nondimensional form, resulting in a multidimensional parameter space spanned by the modified inverse Strouhal number and the modified horizontal Richardson number, as well as relative wind speed and wind direction and the residual runoff. The along-tide momentum equation is then solved for the tidal-mean velocity profile in such a way that it is equated to the sum of the contributions of tidal straining (resulting from the temporal correlation between eddy viscosity and vertical shear), gravitational circulation (resulting from the depth-varying forcing by a constant horizontal buoyancy gradient), wind straining, and depth-mean residual flow (resulting from net freshwater runoff). This definition of tidal straining does not only account for tidal asymmetries resulting from horizontal buoyancy gradients but also from wind straining and residual runoff. For constant eddy viscosity, the well-known estuarine circulation analytical solution with polynomial residual profiles is directly obtained. For vertically parabolic and constant-in-time eddy viscosity, a new analytic solution with logarithmic residual profiles is found, showing that the intensity of the gravitational circulation scales with the horizontal Richardson number. For scenarios with realistic spatially and temporally varying eddy viscosity, a numerical water column model equipped with a state-of-the-art two-equation turbulence closure model is applied to quantify the individual contributions of the various processes to estuarine circulation. The fundamental outcome of this study is that, for irrotational flow with periodic stratification and without wind forcing and residual runoff, the tidal straining is responsible for about two-thirds and gravitational circulation is responsible for about one-third of the estuarine circulation, proportionally dependent on the horizontal Richardson number, and weakly dependent on the Strouhal number. This new and robust result confirms earlier estimates by H. Burchard and H. Baumert, who suggested that tidal straining is the major generation mechanism for estuarine turbidity maxima. However, a sensitivity analysis of the model results to details of the turbulence closure model shows some uncertainty with respect to the parameterization of sheared convection during flood. Increasing down-estuary wind straining and residual runoff reduce the quantitative contribution of tidal straining. For relatively small horizontal Richardson numbers, the tidal straining contribution to estuarine circulation may even be reversed by down-estuary wind straining.

scholarly journals Summer Wind Effects on Coastal Upwelling in the Southwestern Yellow Sea

2021 ◽  
Vol 9 (9) ◽  
pp. 1021
Author(s):  
Bin Wang ◽  
Lei Wu ◽  
Ning Zhao ◽  
Tianran Liu ◽  
Naoki Hirose
Keyword(s):  
Summer Monsoon ◽  
Wind Stress ◽  
Yellow Sea ◽  
Coastal Upwelling ◽  
Circulation Model ◽  
Tidal Mixing ◽  
The Yellow Sea ◽  
Observation Data ◽  
Wind Stress Curl ◽  
Green Tides

The features of coastal upwelling in the southwestern Yellow Sea were investigated based on oceanology data from a research cruise and a regional circulation model. The observation data suggest that a relatively colder and saltier water core exists from the deeper layer to the surface, off the Subei Bank. The concentrations of nutrients also suggest that coastal upwelling is beneficial for nutrient enrichment in the upper layer. The numerical simulations are in good agreement with oceanology observations. Furthermore, sensitivity experiments indicate that, in addition to the tidal-induced upwelling and tidal mixing proposed in previous studies, the summer monsoon is also critical to vertical circulation in the southwestern Yellow Sea. The southwesterly wind stress and positive wind stress curl make considerable contributions to upwelling off the Subei coast compared with tidal motions. Moreover, this study also proposes that changes in the summer monsoon and its curl may have been helpful to the formation of upwelling during the past decade, which may have provided a favorable marine environment for the frequent occurrence of green tides. This study provides a theoretical basis for the mechanisms of coastal upwelling and the nitrogen cycle in the Yellow Sea.

A Second-Order Closure Turbulence Model: New Heat Flux Equations and No Critical Richardson Number

2020 ◽  
Vol 77 (8) ◽  
pp. 2743-2759
Author(s):  
Y. Cheng ◽  
V. M. Canuto ◽  
A. M. Howard ◽  
A. S. Ackerman ◽  
M. Kelley ◽  
...  
Keyword(s):  
Heat Flux ◽  
Turbulence Model ◽  
Richardson Number ◽  
General Circulation ◽  
Circulation Model ◽  
Second Order ◽  
Boundary Layer Height ◽  
Stable Conditions ◽  
Single Column ◽  
Critical Richardson Number

Abstract We formulate a new second-order closure turbulence model by employing a recent closure for the pressure–temperature correlation at the equation level. As a result, we obtain new heat flux equations that avoid the long-standing issue of a finite critical Richardson number. The new, structurally simpler model improves on the Mellor–Yamada and Galperin et al. models; a key feature includes enhanced mixing under stable conditions facilitating agreement with observational, experimental, and high-resolution numerical datasets. The model predicts a planetary boundary layer height deeper than predicted by models with low critical Richardson numbers, as demonstrated in single-column model runs of the GISS ModelE general circulation model.

scholarly journals Phanerozoic paleogeographic, plate tectonic and paleoclimatic reconstructions

1992 ◽  
Vol 6 ◽  
pp. 263-263 ◽  
Author(s):  
Christopher R. Scotese
Keyword(s):  
General Circulation ◽  
Subduction Zones ◽  
Coastal Upwelling ◽  
Hot Spot ◽  
Circulation Model ◽  
Time Interval ◽  
Plate Boundaries ◽  
Plate Tectonic ◽  
Prevailing Wind Direction ◽  
Event Stratigraphy

In 1913, in the concluding remarks to his two volume compendium, Principles of Stratigraphy, Amadeus Grabau wrote, “When the science of Stratigraphy has developed so that its basis is no longer purely or chiefly paleontological, and when the sciences of Lithogenisis and Orogenesis … are given their due share in the comprehensive investigation of the history of the earth, then we may hope that Paleogeography, the youthful daughter science of Stratigraphy will have attained unto that stature that will make it the crowning attraction to the student of earth history.” It has taken nearly 80 years for Grabau's vision to be realized. The fruits of the plate tectonic revolution combined with our new understanding of global eustasy and event stratigraphy, make it now possible to map the changing geography of the earth's surface with unparalleled detail and accuracy.In this poster session, we present 28 paleogeographic maps illustrating the changing configuration of mountains, land, shallow seas, and deep ocean basins during the Phanerozoic. The plate boundaries (spreading ridges, subduction zones, and transform faults) that were active during each time interval are also shown. For the Mesozoic and Cenozoic these plate boundaries are based on a synthesis of linear magnetic anomaly data and fracture zone locations compiled by PALEOMAP Project (International Lithosphere Program). The Mesozoic and Cenozoic orientation of the continents relative to the Earth's axis of rotation has been determined using a combination of paleomagnetic data and hot spot tracks. The location of Paleozoic plate boundaries, though speculative, is based evidence of past subduction and inferred sea floor spreading. The relative longitudinal positions of the continents and the width of the intervening Paleozoic oceans have been adjusted to best explain changing biogeographic and paleoclimatic patterns.The land, sea and mountain distributions portrayed on these 28 paleogeographic reconstructions have been used as input for a series of computer simulations of paleoclimate. The paleoclimatic model, which was developed by C.R. Scotese and M. I. Ross, uses the latitudinal distribution of land and sea, as well as the orientation of ancient mountain belts to predict the distr ibution of high and low pressure cells, prevailing wind direction, relative wetness/dryness, as well as zones of coastal upwelling. This model, which takes a simple parametric approach, makes predictions which are similar to the more robust General Circulation Model (GCM), but requires far less computer resources.

scholarly journals Comparison of GEOS-5 AGCM planetary boundary layer depths computed with various definitions

2014 ◽  
Vol 14 (13) ◽  
pp. 6717-6727 ◽  
Author(s):  
E. L. McGrath-Spangler ◽  
A. Molod
Keyword(s):  
Boundary Layer ◽  
Diffusion Coefficient ◽  
Planetary Boundary Layer ◽  
Richardson Number ◽  
General Circulation ◽  
Circulation Model ◽  
Eddy Diffusion ◽  
Bulk Richardson Number ◽  
Turbulent Length Scale ◽  
Eddy Diffusion Coefficient

Abstract. Accurate models of planetary boundary layer (PBL) processes are important for forecasting weather and climate. The present study compares seven methods of calculating PBL depth in the GEOS-5 atmospheric general circulation model (AGCM) over land. These methods depend on the eddy diffusion coefficients, bulk and local Richardson numbers, and the turbulent kinetic energy. The computed PBL depths are aggregated to the Köppen–Geiger climate classes, and some limited comparisons are made using radiosonde profiles. Most methods produce similar midday PBL depths, although in the warm, moist climate classes the bulk Richardson number method gives midday results that are lower than those given by the eddy diffusion coefficient methods. Additional analysis revealed that methods sensitive to turbulence driven by radiative cooling produce greater PBL depths, this effect being most significant during the evening transition. Nocturnal PBLs based on Richardson number methods are generally shallower than eddy diffusion coefficient based estimates. The bulk Richardson number estimate is recommended as the PBL height to inform the choice of the turbulent length scale, based on the similarity to other methods during the day, and the improved nighttime behavior.

scholarly journals Comparison of GEOS-5 AGCM planetary boundary layer depths computed with various definitions

2014 ◽  
Vol 14 (5) ◽  
pp. 6589-6617 ◽  
Author(s):  
E. L. McGrath-Spangler ◽  
A. Molod
Keyword(s):  
Boundary Layer ◽  
Diffusion Coefficient ◽  
Planetary Boundary Layer ◽  
Richardson Number ◽  
General Circulation ◽  
Circulation Model ◽  
Eddy Diffusion ◽  
Bulk Richardson Number ◽  
Turbulent Length Scale ◽  
Eddy Diffusion Coefficient

Abstract. Accurate models of planetary boundary layer (PBL) processes are important for forecasting weather and climate. The present study compares seven methods of calculating PBL depth in the GEOS-5 atmospheric general circulation model (AGCM) over land. These methods depend on the eddy diffusion coefficients, bulk and local Richardson numbers, and the turbulent kinetic energy. The computed PBL depths are aggregated to the Köppen climate classes, and some limited comparisons are made using radiosonde profiles. Most methods produce similar midday PBL depths, although in the warm, moist climate classes, the bulk Richardson number method gives midday results that are lower than those given by the eddy diffusion coefficient methods. Additional analysis revealed that methods sensitive to turbulence driven by radiative cooling produce greater PBL depths, this effect being most significant during the evening transition. Nocturnal PBLs based on Richardson number are generally shallower than eddy diffusion coefficient based estimates. The bulk Richardson number estimate is recommended as the PBL height to inform the choice of the turbulent length scale, based on the similarity to other methods during the day, and the improved nighttime behavior.

scholarly journals Turbulent viscosity optimized by data assimilation

1999 ◽  
Vol 17 (11) ◽  
pp. 1463-1477 ◽  
Author(s):  
Y. Leredde ◽  
J.-L. Devenon ◽  
I. Dekeyser
Keyword(s):  
Optimal Control ◽  
Data Assimilation ◽  
Coastal Upwelling ◽  
Control Method ◽  
Turbulent Viscosity ◽  
Three Dimensional ◽  
Circulation Model ◽  
Equation Model ◽  
Oceanic Circulation ◽  
Mixing Processes

Abstract. As an alternative approach to classical turbulence modelling using a first or second order closure, the data assimilation method of optimal control is applied to estimate a time and space-dependent turbulent viscosity in a three-dimensional oceanic circulation model. The optimal control method, described for a 3-D primitive equation model, involves the minimization of a cost function that quantifies the discrepancies between the simulations and the observations. An iterative algorithm is obtained via the adjoint model resolution. In a first experiment, a k + L model is used to simulate the one-dimensional development of inertial oscillations resulting from a wind stress at the sea surface and with the presence of a halocline. These results are used as synthetic observations to be assimilated. The turbulent viscosity is then recovered without the k + L closure, even with sparse and noisy observations. The problems of controllability and of the dimensions of the control are then discussed. A second experiment consists of a two-dimensional schematic simulation. A 2-D turbulent viscosity field is estimated from data on the initial and final states of a coastal upwelling event.Key words. Oceanography: general (numerical modelling) · Oceanography: physical (turbulence · diffusion · and mixing processes)

An Eddy-Viscosity Model Sensitized to Curvature and Wall-Roughness Effects for Reynolds-Averaged Closure

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Yang Zhang ◽  
Gang Chen ◽  
Jiakuan Xu
Keyword(s):  
Richardson Number ◽  
Eddy Viscosity ◽  
Plane Channel ◽  
Wall Roughness ◽  
Roughness Effects ◽  
New Model ◽  
Streamline Curvature ◽  
Eddy Viscosity Model ◽  
System Rotation ◽  
Rotating Channel

Abstract This paper presents a new extension of the realizable K−ε model that accounts for streamline curvature, system rotation, and surface roughness. The model is a type of realizable K−ε model, but the transport equations and the eddy-viscosity damping functions are modified, based on the Richardson number and roughness height; the roughness correction covers both the transitional and fully rough regimes. Flows in a rotating channel and a U-bend duct are used to validate the response of the new model to the system rotation and streamline curvature. The flow in a plane channel and the flow over a dune are used to validate the roughness extension. Finally, a rotating channel with rough walls is studied, to test the new model when both rotation and roughness are present.

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