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1.
The predictability of near-coastal currents using a baroclinic unstructured grid model 总被引:1,自引:1,他引:0
Cheryl Ann Blain Mustafa Kemal Cambazoglu Robert S. Linzell Kendra M. Dresback Randall L. Kolar 《Ocean Dynamics》2012,62(3):411-437
A limited domain, coastal ocean forecast system consisting of an unstructured grid model, a meteorological model, a regional
ocean model, and a global tidal database is designed to be globally relocatable. For such a system to be viable, the predictability
of coastal currents must be well understood with error sources clearly identified. To this end, the coastal forecast system
is applied at the mouth of Chesapeake Bay in response to a Navy exercise. Two-day forecasts are produced for a 10-day period
from 4 to 14 June 2010 and compared to real-time observations. Interplay between the temporal frequency of the regional model
boundary forcing and the application of external tides to the coastal model impacts the tidal characteristics of the coastal
current, even contributing a small phase error. Frequencies of at least 3 h are needed to resolve the tidal signal within
the regional model; otherwise, externally applied tides from a database are needed to capture the tidal variability. Spatial
resolution of the regional model (3 vs 1 km) does not impact skill of the current prediction. Tidal response of the system
indicates excellent representation of the dominant M
2 tide for water level and currents. Diurnal tides, especially K
1, are amplified unrealistically with the application of coarse 27-km winds. Higher-resolution winds reduce current forecast
error with the exception of wind originating from the SSW, SSE, and E. These winds run shore parallel and are subject to strong
interaction with the shoreline that is poorly represented even by the 3-km wind fields. The vertical distribution of currents
is also well predicted by the coastal model. Spatial and temporal resolution of the wind forcing including areas close to
the shoreline is the most critical component for accurate current forecasts. Additionally, it is demonstrated that wind resolution
plays a large role in establishing realistic thermal and density structures in upwelling prone regions. 相似文献
2.
Simulation and detection of tsunami signatures in ocean surface currents measured by HF radar 总被引:3,自引:1,他引:2
Klaus-Werner Gurgel Anna Dzvonkovskaya Thomas Pohlmann Thomas Schlick Eric Gill 《Ocean Dynamics》2011,61(10):1495-1507
High-frequency (HF) surface wave radars provide the unique capability to continuously monitor the coastal environment far
beyond the range of conventional microwave radars. Bragg-resonant backscattering by ocean waves with half the electromagnetic
radar wavelength allows ocean surface currents to be measured at distances up to 200 km. When a tsunami propagates from the
deep ocean to shallow water, a specific ocean current signature is generated throughout the water column. Due to the long
range of an HF radar, it is possible to detect this current signature at the shelf edge. When the shelf edge is about 100 km
in front of the coastline, the radar can detect the tsunami about 45 min before it hits the coast, leaving enough time to
issue an early warning. As up to now no HF radar measurements of an approaching tsunami exist, a simulation study has been
done to fix parameters like the required spatial resolution or the maximum coherent integration time allowed. The simulation
involves several steps, starting with the Hamburg Shelf Ocean Model (HAMSOM) which is used to estimate the tsunami-induced
current velocity at 1 km spatial resolution and 1 s time step. This ocean current signal is then superimposed to modelled
and measured HF radar backscatter signals using a new modulation technique. After applying conventional HF radar signal processing
techniques, the surface current maps contain the rapidly changing tsunami-induced current features, which can be compared
to the HAMSOM data. The specific radial tsunami current signatures can clearly be observed in these maps, if appropriate spatial
and temporal resolution is used. Based on the entropy of the ocean current maps, a tsunami detection algorithm is described
which can be used to issue an automated tsunami warning message. 相似文献
3.
Surface currents and winds at the Delaware Bay mouth 总被引:1,自引:0,他引:1
P.A. Muscarella N.P. BartonB.L. Lipphardt Jr. D.E. VeronK.C. Wong A.D. Kirwan Jr. 《Continental Shelf Research》2011,31(12):1282-1293
Knowledge of the circulation of estuaries and adjacent shelf waters has relied on hydrographic measurements, moorings, and local wind observations usually removed from the region of interest. Although these observations are certainly sufficient to identify major characteristics, they lack both spatial resolution and temporal coverage. High-resolution synoptic observations are required to identify important coastal processes at smaller scales. Long observation periods are needed to properly sample low-frequency processes that may also be important. The introduction of high-frequency (HF) radar measurements and regional wind models for coastal studies is changing this situation. Here we analyze synoptic, high-resolution surface winds and currents in the Delaware Bay mouth over an 8-month period (October 2007 through May 2008). The surface currents were measured by two HF radars while the surface winds were extracted from a data-assimilating regional wind model. To illustrate the utility of these monitoring tools we focus on two 45-day periods which previously were shown to present contrasting pictures of the circulation. One, the low-outflow period is from 1 October through 14 November 2007; the other is the high-outflow period from 3 March through 16 April 2008. The large-scale characteristics noted by previous workers are clearly corroborated. Specifically the M2 tide dominates the surface currents, and the Delaware Bay outflow plume is clearly evident in the low frequency currents. Several new aspects of the surface circulation were also identified. These include a map of the spatial variability of the M2 tide (validating an earlier model study), persistent low-frequency cross-mouth flow, and a rapid response of the surface currents to a changing wind field. However, strong wind episodes did not persist long enough to set up a sustained Ekman response. 相似文献
4.
Alexander Port Klaus-Werner Gurgel Joanna Staneva Johannes Schulz-Stellenfleth Emil V. Stanev 《Ocean Dynamics》2011,61(10):1567-1585
Tidal and wind-driven surface currents in the German Bight between shallow mudflats of the North Frisian islands and the island
of Helgoland are studied using coastal high-frequency radar (HFR) observations and hindcasts from a primitive equation numerical
model. The setup of the observational system is described, and estimates of expected measurement errors are given. A quantitative
comparison of numerical model results and observations is performed. The dominant tidal components are extracted from the
two data sources using tidal harmonic analysis and the corresponding tidal ellipses are defined. Results show that the spatial
patterns of different tidal ellipse parameters are consistent in the two data sets. Model sensitivity studies with constant
and variable salinity and temperature distributions are used to study density-related mechanisms of circulation. Furthermore,
the role of the surface wind field in driving the German Bight circulation is investigated using the complex correlation between
wind and surface current vectors. The observed change of the respective correlation patterns from the coastal to open ocean
is shown to be due to a combination of density effects, the coastline and topography. The overall conclusion is that HFR observations
resolve the small-scale and rapidly evolving characteristics of coastal currents well in the studied area and could present
an important component for regional operational oceanography when combined with numerical modelling. Some unresolved issues
associated with the complex circulation and large instability of circulation in front of the Elbe River Estuary justify further
considerations of this area using dedicated surveys and modelling efforts. 相似文献
5.
On the generation of coastline-following grids for ocean models—trade-off between orthogonality and alignment to coastlines 总被引:1,自引:1,他引:0
Regional ocean models usually utilize orthogonal curvilinear grids that are fit to the coastline of the modeled regions. While the orthogonality of the grid is required from the perspective of the numerical algorithms, the alignment to the irregular coastlines improves the characterization of the land-sea distribution and the ocean simulation. In this article, we carry out fractal analysis of two representative coastal regions and discuss the trade-offs between the orthogonality and coastline alignment during the grid generation of these regions. A new grid generation method based on Schwarz-Christoffel conformal mappings is proposed, with automatic coastal boundary retrieval algorithm that generates resolution dependent boundary for grid generation and alleviates the human efforts involved in traditional methods. We show that for the southeastern Pacific region, the coastline is smooth with low fractal dimension and there exists effective trade-off with a coastline boundary that adjusts to the desired grid resolution. On the contrary, there is no effective trade-off for southeast China seas where the coastline is of higher fractal dimension, and a coarser coastline boundary is recommended for better orthogonality with little loss in coastline alignment. Further numerical study of coastal trapped Kelvin waves for the typical regions demonstrate that the new coastline-fitting grids achieve smaller error in numerical dispersion and higher accuracy. Through analysis, we conclude that for grid generation for regional ocean modeling, modelers should bring into consideration of the multi-scale fractal characteristics of the coastline. 相似文献
6.
The problem of resolving or parameterising small-scale processes in oceanographic models and the extent to which small-scale
effects influence the large scale are briefly discussed and illustrated for a number of cases. For tides and surges in near-shore
regions, the advantages of using a graded mesh to resolve coastal and estuarine small-scale features are demonstrated in terms
of a west coast of Britain unstructured mesh model. The effect of mesh resolution upon the accuracy of the overall solution
is illustrated in terms of a finite element model of the Irish Sea and Mersey estuary. For baroclinic motion at high Froude
number, the effect of resolving small-scale topography within a non-hydrostatic model is illustrated in terms of tidally induced
mixing at a single sill, or two closely spaced sills. The question of how to parameterise small-scale non-linear interaction
processes that lead to significant mixing, in a form suitable for coarser grid hydrostatic models, is briefly considered.
In addition, the importance of topographically induced mixing that occurs in the oceanic lateral boundary layer, namely, the
shelf edge upon the large-scale ocean circulation is discussed together with the implications for coarse grid oceanic climate
models. The use of unstructured grids in these models to enhance resolution in shelf-edge regions in a similar manner to that
used in storm surge models to enhance near coastal resolution is suggested as a suitable “way forward” in large-scale ocean
circulation modelling. 相似文献
7.
The rapid expansion of urbanization along the world’s coastal areas requires a more comprehensive and accurate understanding of the coastal ocean. Over the past several decades, numerical ocean circulation models have tried to provide such insight, based on our developing understanding of physical ocean processes. The systematic establishment of coastal ocean observation systems adopting cutting-edge technology, such as high frequency (HF) radar, satellite sensing, and gliders, has put such ocean model predictions to the test, by providing comprehensive observational datasets for the validation of numerical model forecasts. The New York Harbor Observing and Prediction System (NYHOPS) is a comprehensive system for understanding coastal ocean processes on the continental shelf waters of New York and New Jersey. To increase confidence in the system’s ocean circulation predictions in that area, a detailed validation exercise was carried out using HF radar and Lagrangian drifter-derived surface currents from three drifters obtained between March and October 2010. During that period, the root mean square (RMS) differences of both the east–west and north–south currents between NYHOPS and HF radar were approximately 15 cm s?1. Harmonic analysis of NYHOPS and HF radar surface currents shows similar tidal ellipse parameters for the dominant M2 tide, with a mean difference of 2.4 cm s?1 in the semi-major axis and 1.4 cm s?1 in the semi-minor axis and 3° in orientation and 10° in phase. Surface currents derived independently from drifters along their trajectories showed that NYHOPS and HF radar yielded similarly accurate results. RMS errors when compared to currents derived along the trajectory of the three drifters were approximately 10 cm s?1. Overall, the analysis suggests that NYHOPS and HF radar had similar skill in estimating the currents over the continental shelf waters of the Middle Atlantic Bight during this time period. An ensemble-based set of particle tracking simulations using one drifter which was tracked for 11 days showed that the ensemble mean separation generally increases with time in a linear fashion. The separation distance is not dominated by high frequency or short spatial scale wavelengths suggesting that both the NYHOPS and HF radar currents are representing tidal and inertial time scales correctly and resolving some of the smaller scale eddies. The growing ensemble mean separation distance is dominated by errors in the mean flow causing the drifters to slowly diverge from their observed positions. The separation distance for both HF radar and NYHOPS stays below 30 km after 5 days, and the two technologies have similar tracking skill at the 95 % level. For comparison, the ensemble mean distance of a drifter from its initial release location (persistence assumption) is estimated to be greater than 70 km in 5 days. 相似文献
8.
Measurements from recently installed 5 MHz high-frequency radar (CODAR) stations south of Point Arena, California, are used to describe surface current patterns during the upwelling season (June-August 2007). The systems provide hourly current maps on a 5-km grid, covering a region from approximately 10 to 150 km offshore (the continental shelf into the deep ocean). These HF-radar observations provide an unprecedented view of circulation in this “coastal transition zone”, between the wind-driven circulation over the shelf and the California Current circulation offshore. Circulation patterns include: (1) bifurcation of the coastal upwelling jet downstream of Point Arena into an along-shelf (down-coast) branch and an offshore branch, and (2) a large-scale anticyclonic meander that often develops into an eddy-like recirculation south of the bifurcation. The “recirculation” feature extends well offshore, with surface currents 50-100 km from the coast consistently opposing the wind stress. The spatial and temporal evolution of the surface current features during upwelling events affects surface transport from Point Arena to areas in the south, increasing the travel time of a substantial fraction of newly upwelled water from a few days to roughly two weeks. Thus, surface currents even far offshore influence coastal transport of nutrients, phytoplankton and larvae on ecologically relevant timescales, with resultant connectivity patterns very different than implied by a simple examination of the mean flow. 相似文献
9.
The near-sea surface meteorological conditions associated with the Mediterranean heavy precipitation events constitute, on
a short time scale, a strong forcing on the ocean mixed layer. This study addresses the question of the optimal time frequency
of the atmospheric forcing to drive an ocean model in order to make it able to capture the fine scale ocean mixed layer response
to severe meteorological conditions. The coupling time frequency should allow the ocean model to reproduce the formation of
internal low-salty boundary layers due to sudden input of intense precipitation, as well as the cooling and deepening of the
ocean mixed layer through large latent heat fluxes and stress under the intense low-level jet associated with these events.
In this study, the one-dimensional ocean model is driven by 2.4-km atmospheric simulated fields on a case of Mediterranean
heavy precipitation, varying the time resolution of the atmospheric forcing. The results show that using a finer temporal
resolution than 1 h for the atmospheric forcing is not necessary, but a coarser temporal resolution (3 or 6 h) modifies the
event course and intensity perceived by the ocean. Consequently, when using a too coarse temporal resolution forcing, typically
6 h, the ocean model fails to reproduce the ocean mixed layer fine scale response under the heavy rainfall pulses and the
strong wind gusts. 相似文献
10.
Regional turbulence patterns driven by meso- and submesoscale processes in the Caribbean Sea 总被引:1,自引:1,他引:0
The surface ocean circulation in the Caribbean Sea is characterized by the interaction between anticyclonic eddies and the Caribbean Upwelling System (CUS). These interactions lead to instabilities that modulate the transfer of kinetic energy up- or down-cascade. The interaction of North Brazil Current rings with the islands leads to the formation of submesoscale vorticity filaments leeward of the Lesser Antilles, thus transferring kinetic energy from large to small scales. Within the Caribbean, the upper ocean dynamic ranges from large-scale currents to coastal upwelling filaments and allow the vertical exchange of physical properties and supply KE to larger scales. In this study, we use a regional model with different spatial resolutions (6, 3, and 1 km), focusing on the Guajira Peninsula and the Lesser Antilles in the Caribbean Sea, in order to evaluate the impact of submesoscale processes on the regional KE energy cascade. Ageostrophic velocities emerge as the Rossby number becomes O(1). As model resolution is increased submesoscale motions are more energetic, as seen by the flatter KE spectra when compared to the lower resolution run. KE injection at the large scales is greater in the Guajira region than in the others regions, being more effectively transferred to smaller scales, thus showing that submesoscale dynamics is key in modulating eddy kinetic energy and the energy cascade within the Caribbean Sea. 相似文献
11.
12.
Debora Bellafiore Edoardo Bucchignani Silvio Gualdi Sandro Carniel Vladimir Djurdjević Georg Umgiesser 《Ocean Dynamics》2012,62(4):555-568
Modeling studies of future changes in coastal hydrodynamics, in terms of storm surges and wave climate, need appropriate wind
and atmospheric forcings, a necessary requirement for the realistic reproduction of the statistics and the resolution of small
scale features. This work compares meteorological results from different climate models in the Mediterranean area, with a
focus on the Adriatic Sea, in order to assess their capability to reproduce coastal meteorological features and their possibility
to be used as forcings for hydrodynamic simulations. Five meteorological datasets are considered. They are obtained from two
regional climate models, implemented with different spatial resolutions and setups and are downscaled from two different global
climate models. Wind and atmospheric pressure fields are compared with measurements at four stations along the Italian Adriatic
coast. The analysis is carried out both on simulations of the control period 1960–1990 and on the A1B Intergovernmental Panel
for Climate Change scenario projections (2070–2100), highlighting the ability of each model in reproducing the statistical
coastal meteorological behavior and possible changes. The importance of simulated global- and regional-scale meteorological
processes, in terms of correct spatial resolution of the phenomena, is also discussed. Within the Adriatic Sea, the meteorological
climate is influenced by the local orography that controls the strengthening of north-eastern katabatic winds like Bora. Results
show indeed that the increase in spatial resolution provides a more realistic wind forcing for the hydrodynamic simulations.
Moreover, the chosen setup and the global climate models that drive the regional downscalings appear to play an important
role in reproducing correct atmospheric pressure fields. The comparison between scenario and control simulations shows a small
increase in the mean atmospheric pressure values, while a decrease in mean wind speed and in extreme wind events is observed,
particularly for the datasets with higher spatial resolution. Finally, results suggest that an ensemble of downscaled climate
models is likely to provide the most suitable climatic forcings (wind and atmospheric pressure fields) for coastal hydrodynamic
modeling. 相似文献
13.
Tal Ezer 《Ocean Dynamics》2017,67(5):651-664
Two aspects of the interactions between the Gulf Stream (GS) and the bottom topography are investigated: 1. the spatial variations associated with the north-south tilt of mean sea level along the US East Coast and 2. the high-frequency temporal variations of coastal sea level (CSL) that are related to Gulf Stream dynamics. A regional ocean circulation model is used to assess the role of topography; this is done by conducting numerical simulations of the GS with two different topographies–one case with a realistic topography and another case with an idealized smooth topography that neglects the details of the coastline and the very deep ocean. High-frequency oscillations (with a 5-day period) in the zonal wind and in the GS transport are imposed on the model; the source of the GS variability is either the Florida Current (FC) in the south or the Slope Current (SC) in the north. The results demonstrate that the abrupt change of topography at Cape Hatteras, near the point where the GS separates from the coast, amplifies the northward downward mean sea level tilt along the coast there. The results suggest that idealized or coarse resolution models that do not resolve the details of the coastline may underestimate the difference between the higher mean sea level in the South Atlantic Bight (SAB) and the lower mean sea level in the Mid-Atlantic Bight (MAB). Imposed variations in the model’s GS transport can generate coherent sea level variability along the coast, similar to the observations. However, when the bottom topography in the model is modified (or not well resolved), the shape of the coastline and the continental shelf influence the propagation of coastal-trapped waves and impact the CSL variability. The results can explain the different characteristics of sea level variability in the SAB and in the MAB and help understand unexpected water level anomalies and flooding related to remote influence of the GS. 相似文献
14.
Marine radars mounted on ships can provide remarkable insights into ocean behaviour from distances of several kilometres,
placing other in situ observations and the environment around a ship into a wider oceanographic context. It has been known
for some time that it is possible to map shallow water bathymetry and currents using radar image sequences recorded from shore
based stations. However, a long standing question from military and hydrographic communities has been whether such techniques
can be applied to radar data collected by moving vessels. If so, this presents the possibility of mapping large areas of shallow
or coastal seas (albeit with a somewhat coarse horizontal resolution of 50–100 m) prior to the surveying vessel actually having
to travel into potentially uncharted or dangerous shallow water areas. Trial sets of radar data were recorded by the Canadian
Forces Auxiliary Vessel Quest using a Wamos radar digitiser connected to a Decca navigation radar during a number of deployments
around Nova Scotia in 2008 and 2009. Georeferencing corrections derived from the existing ship navigation systems were sufficient
to allow the application of the existing depth inversion analysis designed for static radar installations. This paper presents
the results of bathymetry analyses of two datasets recorded from CFAV Quest while the vessel was travelling at speeds of up
to 14 knots. The bathymetry derived from the radar data compare favourably with independent surveys and with the on-board
echo sounder to depths of approximately 50 m. 相似文献
15.
Rama Rao Karri Abhijit Badwe Xuan Wang Ghada El Serafy Julius Sumihar Vladan Babovic Herman Gerritsen 《Ocean Dynamics》2013,63(1):43-61
Hydrodynamic models are commonly used for predicting water levels and currents in the deep ocean, ocean margins and shelf seas. Their accuracy is typically limited by factors, such as the complexity of the coastal geometry and bathymetry, plus the uncertainty in the flow forcing (deep ocean tide, winds and pressure). In Southeast Asian waters with its strongly hydrodynamic characteristics, the lack of detailed marine observations (bathymetry and tides) for model validation is an additional factor limiting flow representation. This paper deals with the application of ensemble Kalman filter (EnKF)-based data assimilation with the purpose of improving the deterministic model forecast. The efficacy of the EnKF is analysed via a twin experiment conducted with the 2D barotropic Singapore regional model. The results show that the applied data assimilation can improve the forecasts significantly in this complex flow regime. 相似文献
16.
High-resolution X-Band radar measurements of currents,bathymetry and sea state in highly inhomogeneous coastal areas 总被引:1,自引:1,他引:0
Katrin Hessner Konstanze Reichert Jose Carlos Nieto Borge Craig L. Stevens Murray J. Smith 《Ocean Dynamics》2014,64(7):989-998
In this paper, high-resolution wave, current and water depth fields derived by marine X-Band radar are presented for a coastal region of extreme tidal currents in the presence of inhomogeneous bathymetry at the south coast of New Zealand’s North Island. The current and water depth information for the presented location covers an area of approximately 13 km2 with a spatial resolution of 225 m and an update rate of 3 min. The sea state data provides a spatial representation of coastal effects like wave shoaling and refraction forced by bathymetry and current interaction. The near-surface current measurements about 3 km off the coast show expected tidal current pattern with maximum northwest/southeast current of 1.5–2 m/s alongshore. This is in agreement with currents from the RiCOM hydrodynamic model. The spatial resolution of the observed current field exhibits in addition small-scale current features caused by the influence of the local bathymetry. These data demonstrate the insight to be gained in complex, high-energy coastal situations through the use of high-resolution remote sensing techniques. 相似文献
17.
Development of a modelling methodology for simulation of long-term morphological evolution of the southern Baltic coast 总被引:1,自引:1,他引:0
The Darss–Zingst peninsula at the southern Baltic Sea is a typical wave-dominated barrier island system which includes an
outer barrier island and an inner lagoon. The formation of the Darss–Zingst peninsula dates back to the Littorina Transgression
onset about 8,000 cal BP. It originated from several discrete islands, has been reshaped by littoral currents, wind-induced
waves during the last 8,000 years and evolved into a complex barrier island system as today; thus, it may serve as an example
to study the coastal evolution under long-term climate change. A methodology for developing a long-term (decadal-to-centennial)
process-based morphodynamic model for the southern Baltic coastal environment is presented here. The methodology consists
of two main components: (1) a preliminary analysis of the key processes driving the morphological evolution of the study area
based on statistical analysis of meteorological data and sensitivity studies; (2) a multi-scale high-resolution process-based
model. The process-based model is structured into eight main modules. The two-dimensional vertically integrated circulation
module, the wave module, the bottom boundary layer module, the sediment transport module, the cliff erosion module and the
nearshore storm module are real-time calculation modules which aim at solving the short-term processes. A bathymetry update
module and a long-term control function set, in which the ‘reduction’ concepts and technique for morphological update acceleration
are implemented, are integrated to up-scale the effects of short-term processes to a decadal-to-centennial scale. A series
of multi-scale modelling strategies are implemented in the application of the model to the research area. Successful hindcast
of the coastline change of the Darss–Zingst peninsula for the last 300 years validates the modelling methodology. Model results
indicate that the coastline change of the Darss–Zingst peninsula is dominated by mechanisms acting on different time scales.
The coastlines of Darss and the island of Hiddensee are mainly reshaped by long-term effects of waves and longshore currents,
while the coastline change of the Zingst peninsula is due to a combination of long-term effects of waves and short-term effects
caused by wind storms. 相似文献
18.
This study was aimed at modeling, as realistically as possible, the dynamics and thermodynamics of the Iroise Sea by using
the Model for Applications at Regional Scale (MARS), a regional ocean 3D model. The horizontal resolution of the configuration
in use is 2 km with 30 vertical levels. The 3D model of the Iroise Sea is embedded in a larger model providing open boundary
conditions. As regards the atmospheric forcing, the originality of this study is to force the regional ocean model with the
high-resolution (6 km) regional meteorological model, Weather Research and Forecasting (WRF). In addition, as the air surface
temperature is highly sensitive to the sea surface temperature (SST), this regional meteorological model is improved by taking
into account a regional climatologic SST to compute meteorological parameters. By allowing a better coherence between the
SST and the temperature of the atmospheric boundary layer while giving a more realistic representation of heat fluxes exchanged
at the air/sea interface, this forcing constitutes a noticeable improvement of the Iroise Sea modeling. The different sensitivity
tests discussed here pinpoint the importance of entering, in WRF, SST data of sufficiently high quality before the computation
of meteorological forcing when the aim is a study of dynamics and thermodynamics far away from the coast. On the other hand,
when the target is the reproduction of coastal small-scale features in Iroise Sea modeling, the resolution of the meteorological
forcing and the quality of SST are both paramount. The simulation of reference was carried out throughout the Summer and Autumn
of year 2005 to allow comparisons with a campaign of surface current measurements by high-frequency radars conducted at the
same period. 相似文献
19.
20.
Sébastien Blaise Benjamin de Brye Anouk de Brauwere Eric Deleersnijder Eric J. M. Delhez Richard Comblen 《Ocean Dynamics》2010,60(3):535-554
At high Peclet number, the residence time exhibits a boundary layer adjacent to incoming open boundaries. In a Eulerian model,
not resolving this boundary layer can generate spurious oscillations that can propagate into the area of interest. However,
resolving this boundary layer would require an unacceptably high spatial resolution. Therefore, alternative methods are needed
in which no grid refinement is required to capture the key aspects of the physics of the residence time boundary layer. An
extended finite element method representation and a boundary layer parameterisation are presented and tested herein. It is
also explained how to preserve local consistency in reversed time simulations so as to avoid the generation of spurious residence
time extrema. Finally, the boundary layer parameterisation is applied to the computation of the residence time in the Scheldt
Estuary (Belgium/The Netherlands). This timescale is simulated by means of a depth-integrated, finite element, unstructured
mesh model, with a high space–time resolution. It is seen that the residence time temporal variations are mainly affected
by the semi-diurnal tides. However, the spring–neap variability also impacts the residence time, particularly in the sandbank
and shallow areas. Seasonal variability is also observed, which is induced by the fluctuations over the year of the upstream
flows. In general, the residence time is an increasing function of the distance to the mouth of the estuary. However, smaller-scale
fluctuations are also present: they are caused by local bathymetric features and their impact on the hydrodynamics. 相似文献