共查询到20条相似文献，搜索用时 906 毫秒
1.
George R. HalliwellJr Alexander Barth Robert H. Weisberg Patrick Hogan Ole Martin Smedstad James Cummings 《Ocean Dynamics》2009,59(1):139-155
Nested non-assimilative simulations of the West Florida Shelf for 2004–2005 are used to quantify the impact of initial and
boundary conditions provided by Global Ocean Data Assimilation Experiment ocean products. Simulations are nested within an
optimum interpolation hindcast of the Atlantic Ocean, the initial test of the US Navy Coupled Ocean Data Assimilation system
for the Gulf of Mexico, and a global ocean hindcast that used the latter assimilation system. These simulations are compared
to one that is nested in a non-assimilative Gulf of Mexico model to document the importance of assimilation in the outer model.
Simulations are evaluated by comparing model results to moored Acoustic Doppler Current Profiler measurements and moored sea
surface temperature time series. The choice of outer model has little influence on simulated velocity fluctuations over the
inner and middle shelf where fluctuations are dominated by the deterministic wind-driven response. Improvement is documented
in the representation of alongshore flow variability over the outer shelf, driven in part by the intrusion of the Loop Current
and associated cyclones at the shelf edge near the Dry Tortugas. This improvement was realized in the simulation nested in
the global ocean hindcast, the only outer model choice that contained a realistic representation of Loop Current transport
associated with basin-scale wind-driven gyre circulation and the Atlantic Meridional Overturning Circulation. For temperature,
the non-assimilative outer model had a cold bias in the upper ocean that was substantially corrected in the data-assimilative
outer models, leading to improved temperature representation in the simulations nested in the assimilative outer models. 相似文献
2.
Numerical modeling with application to tracking marine debris 总被引：1，自引：0，他引：1
Potemra JT 《Marine pollution bulletin》2012,65(1-3):42-50
This paper describes different numerical models of ocean circulation the output of which can be applied to study patterns and pathways of drifting marine debris. The paper focuses on model output that is readily available rather than on numerical models that could be configured and run locally. These include operational models from the US Navy (the Navy Layered Ocean Model (NLOM), Coastal Ocean Model (NCOM), and Hybrid Coordinate Ocean Model (HYCOM)), data assimilating reanalysis models (the Simple Ocean Data Assimilation (SODA), the Global Ocean Data Assimilation Experiment (GODAE) models), and the European Center for Medium-Range Weather Forecasts (ECMWF) ocean reanalysis (Ocean Reanalysis System, ECMWF/ORA-S3). The paper describes the underlying physics in each model system, limitations, and where to obtain the model output. 相似文献
3.
Teddy R. Holt James A. Cummings Craig H. Bishop James D. Doyle Xiaodong Hong Sue Chen Yi Jin 《Ocean Dynamics》2011,61(11):1937-1954
A coupled ocean–atmosphere mesoscale ensemble prediction system has been developed by the Naval Research Laboratory. This paper describes the components and implementation of the system and presents baseline results from coupled ensemble simulations for two tropical cyclones. The system is designed to take into account major sources of uncertainty in: (1) non-deterministic dynamics, (2) model error, and (3) initial states. The purpose of the system is to provide mesoscale ensemble forecasts for use in probabilistic products, such as reliability and frequency of occurrence, and in risk management applications. The system components include COAMPS® (Coupled Ocean/Atmosphere Mesoscale Prediction System) and NCOM (Navy Coastal Ocean Model) for atmosphere and ocean forecasting and NAVDAS (NRL Atmospheric Variational Data Assimilation System) and NCODA (Navy Coupled Ocean Data Assimilation) for atmosphere and ocean data assimilation. NAVDAS and NCODA are 3D-variational (3DVAR) analysis schemes. The ensembles are generated using separate applications of the Ensemble Transform (ET) technique in both the atmosphere (for moving or non-moving nests) and the ocean. The atmospheric ET is computed using wind, temperature, and moisture variables, while the oceanographic ET is derived from ocean current, temperature, and salinity variables. Estimates of analysis error covariance, which is used as a constraint in the ET, are provided by the ocean and atmosphere 3DVAR assimilation systems. The newly developed system has been successfully tested for a variety of configurations, including differing model resolution, number of members, forecast length, and moving and fixed nest options. Results from relatively coarse resolution (～27-km) ensemble simulations of Hurricanes Hanna and Ike demonstrate that the ensemble can provide valuable uncertainty information about the storm track and intensity, though the ensemble mean provides only a small amount of improved predictive skill compared to the deterministic control member. 相似文献
4.
This study examines seasonal circulation, hydrography, and associated spatial variability over the inner shelf of the northern South China Sea (NSCS) using a nested-grid coastal ocean circulation model. The model external forcing consists of tides, atmospheric forcing, and open boundary conditions based on the global ocean circulation and hydrography reanalysis produced by the Hybrid Coordinate Ocean model. Five numerical experiments are conducted with different combinations of external forcing functions to examine main physical processes affecting the seasonal circulation in the study region. Model results demonstrate that the monthly mean circulation in the study region features the Guangdong Coastal Current (GCC) over coastal waters and the South China Sea Warm Current (SCSWC) in the offshore deep waters. The GCC produced by the model flows nearly southwestward in winter months and northwestward in summer months, which agrees with previous studies. The SCSWC flows roughly northeastward and is well defined in summer months. In winter months, by comparison, the SCSWC is superseded by the southwestward strong wind-driven currents. Analysis of model results in five different experiments demonstrates that the monthly mean circulation over coastal and inner shelf waters of the NSCS can be approximated by barotropic currents forced by the southwestward monsoon winds in winter months. In summer months, by comparison, the monthly mean circulation in the study region is affected significantly by baroclinic dynamics associated with freshwater runoff from the Pearl River and advection of warm and saline waters carried by the SCSWC over the NSCS. 相似文献
5.
The finite volume coastal ocean model downscaling ocean reanalysis and forecast data provided by the Japan Coastal Ocean Predictability
Experiment (JCOPE2) are used to forecast sudden Kuroshio water intrusion events (kyucho) induced by frontal waves amplified
south of the Bungo Channel in 2010. Two-month hindcast computations give initial conditions of the following 3-month forecasts
computations which consist of ten ensemble members. The temperature time series computed by these ten members are averaged
to compare with that actually observed in the Bungo Channel, where sudden temperature rises related to kyucho events are remarkable
in February, August, and September. Overall, the intense kyucho events actually observed in these months are predicted successfully.
However, intense kyucho events are forecasted frequently during the period of May through June even though intense kyucho
events are absent during this period in the actual ocean. It is suggested that the present downscaling forecast model requires
reliable lateral boundary conditions provided by JCOPE2 data to which numerous Argo data are assimilated to enhance the accuracy.
In addition, it seems likely that the model accuracy is reduced by small eddies moving along the shelf break. 相似文献
6.
We revisit the surge of November 1977, a storm event which caused damage on the Sefton coast in NW England. A hindcast has been made with a coupled surge-tide-wave model, to investigate whether a wave-dependent surface drag is necessary for accurate surge prediction, and also if this can be represented by an optimised Charnock parameter. The Proudman Oceanographic Laboratory Coastal Modelling System-Wave Model (POLCOMS-WAM) has been used to model combined tides, surges, waves and wave-current interaction in the Irish Sea on a 1.85 km grid. This period has been previously thoroughly studied, e.g. Jones and Davies [Jones, J.E., Davies, A.M., 1998. Storm surge computations for the Irish Sea using a three-dimensional numerical model including wave-current interaction. Continental Shelf Research 18(2), 201–251] and we build upon this previous work to validate the POLCOMS-WAM model to test the accuracy of surge elevation predictions in the study area. A one-way nested approach has been set up from larger scale models to the Irish Sea model. It was demonstrated that (as expected) swell from the North Atlantic does not have a significant impact in the eastern Irish Sea. To capture the external surge generated outside of the Irish Sea a (1/9° by 1/6°) model extending beyond the continental shelf edge was run using the POLCOMS model for tide and surge. 相似文献
7.
We explore the ocean circulation estimates obtained by assimilating observational products made available by the Global Ocean
Data Assimilation Experiment (GODAE) and other sources in an incremental, four-dimensional variational data assimilation system
for the Intra-Americas Sea. Estimates of the analysis error (formally, the inverse Hessian matrix) are computed during the
assimilation procedure. Comparing the impact of differing sea surface height and sea surface temperature products on both
the final analysis error and difference between the model state estimates, we find that assimilating GODAE and non-GODAE products
yields differences between the model and observations that are comparable to the differences between the observation products
themselves. While the resulting analysis error estimates depend on the configuration of the assimilation system, the basic
spatial structures of the standard deviations of the ocean circulation estimates are fairly robust and reveal that the assimilation
procedure is capable of reducing the circulation uncertainty when only surface data are assimilated. 相似文献
8.
Vassiliki H. Kourafalou Ge Peng HeeSook Kang Patrick J. Hogan Ole-Martin Smedstad Robert H. Weisberg 《Ocean Dynamics》2009,59(1):47-66
The South Florida Hybrid Coordinate Ocean Model (SoFLA-HYCOM) encompasses a variety of coastal regions (the broad Southwest
Florida shelf, the narrow Atlantic Keys shelf, the shallow Florida Bay, and Biscayne Bay) and deep regions (the Straits of
Florida), including Marine Protected Areas (the Florida Keys Marine Sanctuary and the Dry Tortugas Ecological Reserve). The
presence of the strong Loop Current/Florida Current system and associated eddies connects the local and basin-wide dynamics.
A multi-nested approach has been developed to ensure resolution of coastal-scale processes and proper interaction with the
large scale flows. The simulations are free running and effects of data assimilation are introduced through boundary conditions
derived from Global Ocean Data Assimilation Experiment products. The study evaluates the effects of boundary conditions on
the successful hindcasting of circulation patterns by a nested model, applied on a dynamically and topographically complex
shelf area. Independent (not assimilated) observations are employed for a quantitative validation of the numerical results.
The discussion of the prevailing dynamics that are revealed in both modeled and observed patterns suggests the importance
of topography resolution and local forcing on the inner shelf to middle shelf areas, while large scale processes are found
to dominate the outer shelf flows. The results indicate that the successful hindcasting of circulation patterns in a coastal
area that is characterized by complex topography and proximity to a large scale current system requires a dynamical downscaling
approach, with simulations that are nested in a hierarchy of data assimilative outer models. 相似文献
9.
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11.
The present study investigates the sensitivity of the COupled Hydrodynamical–Ecological model for REgioNal and Shelf seas (COHERENS) to predict sea surface temperature (SST) patterns in the Sea of Iroise (western end of French Brittany) in relation to the spatial and temporal resolutions of open boundary conditions (OBCs). Two sources of daily operational OBCs of temperature are considered, derived from (1) the Mercator Global Ocean and (2) the Iberian Biscay Irish analysis and forecasting systems delivering predictions at spatial resolutions of 1/12° and 1/36°, respectively. Coastal model performance is evaluated by comparing SST predictions with recently available field data collected (1) along the route of a vessel travelling between the coast and the isle of Ushant and (2) at two offshore stations. The comparison is extended to SST spatial distribution derived from remote-sensing observations. The influence of OBC spatial resolution is exhibited in the north-eastern area of the Sea of Iroise in relation to the intrusion of cold surface waters. OBC temporal resolution is found to have a lower impact advocating for the implementation of climatological temperature forcings to predict major SST patterns in the Sea of Iroise. 相似文献
12.
It is believed that, in the future, the intensity and frequency of extreme coastal flooding events may increase as a result
of climate change. The Natural Environment Research Council (NERC) Flood Risk from Extreme Events (FREE) project, Coastal
Flooding by Extreme Events and EU FP7 Morphological Impacts and Coastal Risks Induced by Extreme Storm Events project are
investigating the flood risks in the eastern Irish Sea, an area that includes most of England’s coastal types. Using a previously
modelled and validated historical extreme surge event, in November 1977, we now investigate the changes in peak surge as a
result of possible future climate conditions. In order to simulate the surge, we have set up a one-way nested approach, using
the Proudman Oceanographic Laboratory Coastal Ocean Modelling System 3D baroclinic model, from a domain covering the whole
NW European continental shelf, through to a 1.85 km Irish Sea model; both areas are forced by tides, atmospheric pressure
and winds. We use this modelling system to investigate the impact of enhanced wind velocities and increased sea levels on
the peak surge elevation and residual current pattern. The results show that sea level rise has greater potential to increase
surge levels than increased wind speeds. 相似文献
13.
The regional ocean model system (ROMS) is used to downscale a 26-year period of the twentieth century 20C3M experiment from
the global coupled Bergen climate model (BCM) for the North Sea. Compared to an observational-based climatology, BCM have
good results on the mean temperature, except for too low winter temperature. This is connected to a too weak inflow of Atlantic
water. The downscaling gives added value to the BCM results by providing regional details, doubling the Atlantic inflow, and
improving the mean winter temperature. For mean salinity, BCM has values very close to the climatology, whereas the downscaling
becomes too fresh. The downscaling, however, improves the sea surface salinity, the vertical structure, and the Norwegian
Coastal Current. It is concluded that the downscaling procedure as presented here is a suitable tool for assessing the future
Atlantic inflow and sea temperature in the North Sea based on a global climate projection. 相似文献
14.
Effects of convection instability due to incompatibility between ocean dynamics and surface forcings
The study demonstrates that an incompatibility between a surface temperature climatology and a given ocean model, into which the climatology is assimilated via Haney restoration, can cause model ocean climate drift and interdecadal oscillations when the ocean is switched to a weaker restoration. This is made using an idealized Atlantic Ocean model driven by thermal and wind forcing only. Initially, the temperature climatology is forcefully assimilated into the model, and an implied heat flux field is diagnosed. During this stage any incompatibility is suppressed. The restoring boundary condition is then switched to a new forcing consisting of a part of the diagnosed flux and a part of the restoring forcing in such a way that at the moment of the switching the heat flux is identical to that prior to the switching. Under this new forcing condition, the incompatibility becomes manifest, causing changes in convection patterns, and producing drift and interdecadal oscillations. The mechanisms are described. 相似文献
15.
Long-term variability of heat content (HC) in the upper 1,000 m of the Arctic Ocean is investigated using surface and subsurface
temperature and current data during 1958–2005 compiled by Simple Ocean Data Assimilation. Annual cycle of the Arctic Ocean
HC is controlled primarily by the negative and positive excursions in net upper ocean heat flux, while the inter-annual variability
is mainly associated with meridional thermal advection from the North Atlantic Ocean. Variability in HC is experienced as
a basin-wide cooling/warming in association with the Arctic Oscillation on a decadal time scale. In the first three dominant
modes of Empirical Orthogonal Function, the maximum amplitude of HC variability occurs in the Greenland–Norwegian Sea and
Eurasian Basin. In general, HC showed increasing trend during 1958–2005 indicating continuous warming with regional variations
in magnitude. 相似文献
16.
We utilise a global finite-element sea ice–ocean model (FESOM), focused on the Antarctic marginal seas, to analyse projections of ice shelf basal melting in a warmer climate. Ice shelf–ocean interaction is described using a three-equation system with a diagnostic computation of temperature and salinity at the ice–ocean interface. A tetrahedral mesh with a minimumhorizontal resolution of 4 km and hybrid vertical coordinates is used. Ice shelf draft, cavity geometry, and global ocean bathymetry have been derived from the RTopo-1 data set. The model is forced with the atmospheric output from two climate models: (1) the Hadley Centre Climate Model (HadCM3) and (2) Max Planck Institute’s ECHAM5/MPI-OM coupled climate model. Results from experiments forced with their twentieth century output are used to evaluate the modelled present-day ocean state. Sea ice coverage is largely realistic in both simulations; modelled ice shelf basal melt rates compare well with observations in both cases, but are consistently smaller for ECHAM5/MPI-OM. Projections for future ice shelf basal melting are computed using atmospheric output for the Intergovernmental Panel on Climate Change (IPCC) scenarios E1 and A1B. In simulations forced with ECHAM5 data, trends in ice shelf basal melting are small. In contrast, decreasing convection along the Antarctic coast in HadCM3 scenarios leads to a decreasing salinity on the continental shelf and to intrusions of warm deep water of open ocean origin. In the case of the Filchner–Ronne Ice Shelf (FRIS), this water reaches deep into the cavity, so that basal melting increases by a factor of 4 to 6 compared to the present value of about 90 Gt/year. By the middle of the twenty-second century, FRIS becomes the dominant contributor to total ice shelf basal mass loss in these simulations. Our results indicate that the surface freshwater fluxes on the continental shelves may be crucial for the future of especially the large cold water ice shelves in the Southern Ocean. 相似文献
17.
《中国科学:地球科学(英文版)》2017,(3)
The salinity boundary condition at the ocean surface plays an important role in the stability of long-term integrations of an oceanic general circulation model(OGCM) and in determining its equilibrium solutions.This study presents a new formulation of the salt flux calculation at the ocean surface based on physical processes of salt exchange at the air-sea interface.The formulation improves the commonly used virtual salt flux with constant reference salinity by allowing for spatial correlations between surface freshwater flux and sea-surface salinity while preserving the conservation of global salinity.The new boundary condition is implemented in the latest version of the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics Climate Ocean Model version 2(LICOM2.0).The impact of the new boundary condition on the equilibrium simulations of the model is presented.It is shown that the new formulation leads to a stronger Atlantic meridional overturning circulation(AMOC) that is closer to observational estimates.It also slightly improves poleward heat transport by the oceans in both the Atlantic and the global oceans. 相似文献
18.
Arne Melsom 《Ocean Dynamics》2005,55(3-4):338-350
A set of two simulation ensembles of the ocean circulation in the North Sea, the Skagerrak and bordering seas has been run
for the ten year period that started in January 1992. The ensembles differed only in the horizontal grid resolution. The main
purposes of this investigation are (1) to quantify the variability that can be expected in multi-year simulations due to noise-like
perturbations in the initial fields, and (2) to examine the robustness of model results for mesoscale features that form on
the front between the Norwegian Coastal Current and water masses that are of an Atlantic Ocean origin. It is shown that the
model resolution has a substantial impact on the ensemble variability, and that the role of small perturbations become more
significant as the grid mesh is refined. Nevertheless, it is demonstrated that in a region to the west of the southern tip
of Norway, eddies are occasionally found in the same positions at the same time in the results from all members of the ensembles.
This is particularly the case in the aftermath of outbreak events of low salinity water masses from the Skagerrak into the
North Sea. 相似文献
19.
This study explored the spatial patterns of winter predictability barrier (WPB)-related optimal initial errors and optimal precursors for positive Indian Ocean dipole (IOD) events, and the associated physical mechanisms for their developments were analyzed using the Simple Ocean Data Assimilation dataset. Without consideration of the effects of model errors on “predictions,” it was assumed that different “predictions” are caused by different initial conditions. The two types of WPB-related optimal initial errors are almost opposite for the start months of July (–1) and July (0), although they both present a west-east dipole pattern in the tropical Indian Ocean, with the maximum errors located at the thermocline depth. Bjerknes feedback and ocean waves play important roles in the growth of prediction errors. These two physical mechanisms compete during July–December and ocean waves dominate during January–June. The spatial patterns of optimal precursors and the physical mechanisms for their developments are similar to those of WPB-related optimal initial errors. It is worth noting that large values of WPB-related optimal initial errors and optimal precursors are concentrated within a few locations, which probably represent the sensitive areas of targeted observations for positive IOD events. The great similarities between WPB-related optimal initial errors and optimal precursors suggest that were intensive observations performed over these areas, this would not only reduce initial errors and thus, prediction errors, but it would also permit the detection of the signal of IOD events in advance, greatly improving the forecast skill of positive IOD events. 相似文献
20.
A high-resolution (1/60°), three-dimensional numerical circulation model of the Cariaco Basin (Venezuela) is constructed by
nesting the Regional Ocean Modeling System (ROMS) in the 1/12° global Hybrid Coordinate Ocean Model (HYCOM). A new bathymetry,
computed by merging DBDB2 data and in situ depth measurements using optimal interpolation, is described. This new bathymetry
corrects the depth of the channels that connect the Cariaco Basin with the open ocean and which play a very important role
in the basin circulation. Results from a 2004 ROMS hindcast are presented. Observations (temperature, salinity, and currents)
are used to validate the model results before using the model to describe the annual cycle of the Cariaco Basin and the interactions
between the basin and the open ocean. Two modes of interaction are described, the first being the meanders and eddies that
travel westward with the Caribbean Current, and the second being a subsurface eastward current that flows along the north
coast of South America. The circulation path within the basin is directly related to the intensity of this current. Both mechanisms
described play a role in the ventilation of the basin. The present study is also an example of the feasibility of one of the
objectives of GODAE (Global Ocean Data Assimilation Experiment): downscaling from a large-scale model to a regional model.
In particular, the nesting ratio of 5 used in this work demonstrates that a high-resolution model can be successfully nested
in HYCOM. 相似文献