scholarly journals High-resolution nested model for the Lebanese coastal area, Eastern Mediterranean: implementation and climatological runs

2006 ◽  
Vol 3 (3) ◽  
pp. 373-396 ◽  
Author(s):  
N. Kabbara ◽  
R. Sorgente ◽  
S. Natale ◽  
D. R. Hayes ◽  
G. Zodiatis
Keyword(s):  
High Resolution ◽  
Eastern Mediterranean ◽  
Ocean Model ◽  
Levantine Basin ◽  
Resolution Model ◽  
Coarse Model ◽  
Shelf Region ◽  
Horizontal Grid ◽  
Lebanese Coast ◽  
Circulation Characteristics

Abstract. As a part of the project Mediterranean Network to Assess and Upgrade Monitoring and Forecasting Activity in the Region (MAMA) we implemented a high resolution nested hydrodynamic model (1/40° horizontal grid, 16 sigma levels) for the coastal, shelf and open sea areas off the Lebanese coast, East Levantine Basin of the Eastern Mediterranean Sea. The Lebanese Shelf Model (LSM) is a version of the Princeton Ocean Model (POM). It is nested in a coarse resolution model the Aegean Levantine Eddy Resolving Model (1/20° horizontal grid, 25 sigma levels), ALERMO, that covers the Eastern Mediterranean. The nesting is one way so that velocity, temperature, and salinity along the open boundaries are interpolated from the relevant coarse model variables. Numerical simulations have been carried out under climatological surface and lateral forcing. Due to the relatively small domain, the results closely follow the simulation of the intermediate model with more details especially over the narrow shelf region. Simulations reproduce main circulation features and coastal circulation characteristics over the eastern Levantine shelf. This paper describes the modeling system setup, compares the simulations with the corresponding results of the coarse model ALERMO, and with the observed climatological circulation characteristics in the Levantine Basin off the Lebanese coast.

scholarly journals Central Mediterranean Sea forecast: effects of high-resolution atmospheric forcings

2006 ◽  
Vol 3 (3) ◽  
pp. 637-669 ◽  
Author(s):  
S. Natale ◽  
R. Sorgente ◽  
S. Gaberšek ◽  
A. Ribotti ◽  
A. Olita
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Regional Scale ◽  
Circulation Model ◽  
Surface Current ◽  
Ocean Model ◽  
Central Mediterranean ◽  
Resolution Model ◽  
Atmospheric Forcings ◽  
Very High

Abstract. Ocean forecasts over the Central Mediterranean, produced by a near real time regional scale system, have been evaluated in order to assess their predictability. The ocean circulation model has been forced at the surface by a medium, high or very high resolution atmospheric forcing. The simulated ocean parameters have been compared with satellite data and they were found to be generally in good agreement. High and very high resolution atmospheric forcings have been able to form noticeable, although short-lived, surface current structures, due to their ability to detect transient atmospheric disturbances. The existence of the current structures has not been directly assessed due to lack of measurements. The ocean model in the slave mode was not able to develop dynamics different from the driving coarse resolution model which provides the boundary conditions.

High-resolution model Verification Evaluation (HiVE). Part 1: Using neighbourhood techniques for the assessment of ocean model forecast skill

2020 ◽  
Author(s):  
Jan Maksymczuk ◽  
Ric Crocker ◽  
Marion Mittermaier ◽  
Christine Pequignet
Keyword(s):  
High Resolution ◽  
Weather Prediction ◽  
Ocean Model ◽  
Forecast Skill ◽  
Model Verification ◽  
Model Forecast ◽  
Verification Methods ◽  
Resolution Model ◽  
The Right ◽  
Spatial Verification

<div> <p>HiVE is a CMEMS funded collaboration between the atmospheric Numerical Weather Prediction (NWP) verification and the ocean community within the Met Office, aimed at demonstrating the use of spatial verification methods originally developed for the evaluation of high-resolution NWP forecasts, with CMEMS ocean model forecast products. Spatial verification methods provide more scale appropriate ways to better assess forecast characteristics and accuracy of km-scale forecasts, where the detail looks realistic but may not be in the right place at the right time. As a result, it can be the case that coarser resolution forecasts verify better (e.g. lower root-mean-square-error) than the higher resolution forecast. In this instance the smoothness of the coarser resolution forecast is rewarded, though the higher-resolution forecast may be better. The project utilised open source code library known as Model Evaluation Toolkit (MET) developed at the US National Center for Atmospheric Research. </p> </div><div> <p> </p> </div><div> <p>This project saw, for the first time, the application of spatial verification methods to sub-10 km resolution ocean model forecasts. The project consisted of two parts. Part 1 describes an assessment of the forecast skill for SST of CMEMS model configurations at observing locations using an approach called HiRA (High Resolution Assessment). Part 2 is described in the companion poster to this one.  </p> </div><div> <p> </p> </div><div> <p>HiRA is a single-observation-forecast-neighbourhood-type method which makes use of commonly used ensemble verification metrics such as the Brier Score (BS) and the Continuous Ranked Probability Score (CRPS). In this instance all model grid points within a predefined neighbourhood of the observing location are considered equi-probable outcomes (or pseudo-ensemble members) at the observing location. The technique allows for an inter-comparison of models with different grid resolutions as well as between deterministic and probabilistic forecasts in an equitable and consistent way. In this work it has been applied to the CMEMS products delivered from the AMM7 (~7km) and AMM15 (~1.5km) model configurations for the European North West Shelf that are provided by the Met Office. </p> </div><div> <p> </p> </div><div> <p>It has been found that when neighbourhoods of equivalent extent are compared for both configurations it is possible to show improved forecast skill for SST for the higher resolution AMM15 both on- and off-shelf, which has been difficult to demonstrate previously using traditional metrics. Forecast skill generally degrades with increasing lead time for both configurations, with the off-shelf results for the higher resolution model showing increasing benefits over the coarser configuration. </p> </div>

Spreading dynamics of central Labrador and Irminger Sea Waters

2020 ◽  
Author(s):  
Patricia Handmann ◽  
Martin Visbeck ◽  
Arne Biastoch
Keyword(s):  
High Resolution ◽  
Ocean Model ◽  
Shelf Break ◽  
Labrador Sea ◽  
Mean Velocity ◽  
The North ◽  
Irminger Sea ◽  
First Results ◽  
Resolution Model ◽  
High Resolution Model

<p>Water mass formation in the Subpolar North Atlantic and successive southward export, connects high latitudes with lower latitudes, as a part of the lower Atlantic meridional overturning (AMOC) limb. The role of regional importance, in particular the respective roles of the Labrador and Irminger Sea, in this process are in debate. </p><p>This study analyses pathways connecting the Labrador and Irminger Sea in detail, using simulated Lagrangian particle trajectories. To give further insight on interconnectivity and flow patterns we used two setups with different velocity fields, a high-resolution ocean model (VIKING20X) and a gridded Argo float displacement climatology. Both setups indicate two distinct pathways with interconnectivity on the order of 20% of the total amount of seeded particles between the Labrador Sea and Irminger Sea. One pathway is following the recirculation in the Labrador Sea along the Greenland shelf break; the other is along the Newfoundland shelf break turning to the north/northwest at the Orphan-Knoll region towards the central Irminger Sea. For the Argo based advective-diffusive particle trajectory integration a 2.5–3.5 year travel time scale was derived between the Labrador and the Irminger Sea, while the experiments with the temporarily varying high-resolution model output revealed significantly shorter spreading times of about 1.5–2 years. While both pathways are represented in either setup, the pathway following the Newfoundland shelf break is populated stronger in the model-based experiments. In general we found that connectivity between the two regions is weaker in the experiments based on the climatological mean velocity output of the model than in those based on the Argo derived fields, first results indicate that this is due to stronger boundary currents and a weaker recirculation in the Labrador Sea.</p>

scholarly journals Intrusion of coastal waters into the pelagic eastern Mediterranean: in situ and satellite-based characterization

2013 ◽  
Vol 10 (5) ◽  
pp. 3349-3357 ◽  
Author(s):  
S. Efrati ◽  
Y. Lehahn ◽  
E. Rahav ◽  
N. Kress ◽  
B. Herut ◽  
...  
Keyword(s):  
High Resolution ◽  
Coastal Waters ◽  
Eastern Mediterranean ◽  
Propagation Speed ◽  
Surface Currents ◽  
Sampling Strategies ◽  
Open Sea ◽  
Levantine Basin ◽  
Transport Barriers

Abstract. A combined dataset of near-real-time multi-satellite observations and in situ measurements from a high-resolution survey is used for characterizing physical-biogeochemical properties of a patch stretching from the coast to the open sea in the Levantine Basin (LB) of the eastern Mediterranean (EM). Spatial analysis of the combined dataset indicates that the patch is a semi-enclosed system, bounded within the mixed layer and separated from ambient waters by transport barriers induced by horizontal stirring. As such, the patch is characterized by physical-biogeochemical properties that significantly differ from those of the waters surrounding it, with lower salinity and higher temperatures, concentrations of silicic acid and chlorophyll a, and abundance of Synechococcus and picoeukaryote cells. Based on estimates of patch dimensions (∼40 km width and ∼25 m depth) and propagation speed (∼0.09 m s−1), the volume flux associated with the patch is found to be on the order of 0.1 Sv. Our observations suggest that horizontal stirring by surface currents is likely to have an important impact on the ultra-oligotrophic Levantine Basin ecosystem, through (1) transport of nutrients and coastally derived material, and (2) formation of local, dynamically isolated niches. In addition, this work provides a satellite-based framework for planning and executing high-resolution sampling strategies in the interface between the coast and the open sea.

scholarly journals High resolution nested model for the Cyprus, NE Levantine Basin, eastern Mediterranean Sea: implementation and climatological runs

2003 ◽  
Vol 21 (1) ◽  
pp. 221-236 ◽  
Author(s):  
G. Zodiatis ◽  
R. Lardner ◽  
A. Lascaratos ◽  
G. Georgiou ◽  
G. Korres ◽  
...  
Keyword(s):  
High Resolution ◽  
Mediterranean Sea ◽  
General Circulation ◽  
Eastern Mediterranean ◽  
Pilot Project ◽  
Ocean Model ◽  
Eastern Mediterranean Sea ◽  
Coastal Shelf ◽  
Forecasting System ◽  
The Mediterranean

Abstract. A high resolution nested flow model for the coastal, shelf and open sea areas of the Cyprus Basin, NE Levantine, eastern Mediterranean Sea is implemented to fulfil the objectives of the Mediterranean Forecasting System Pilot Project, funded by the EU. The Cyprus coastal ocean model is nested entirely within a coarse regional grid model of the eastern Mediterranean Sea, using the MODB climatology for initialisation and the ECMWF perpetual year surface forcing. The nested simulations of the Cyprus model were able to reproduce, with greater detail, flow features similar to those of the coarse grid regional model. The project results show the feasibility of the approach for the development of an operational forecasting system in the Mediterranean Sea, particularly in the Cyprus coastal/shelf sea area. Key words. Oceanography: general (descriptive and regional oceanography; numerical modelling) Oceanography: physical (general circulation)

scholarly journals Intrusion of coastal waters into the pelagic Eastern Mediterranean: in situ and satellite-based characterization

2012 ◽  
Vol 9 (12) ◽  
pp. 17975-17997
Author(s):  
S. Efrati ◽  
Y. Lehahn ◽  
E. Rahav ◽  
N. Kress ◽  
B. Herut ◽  
...  
Keyword(s):  
High Resolution ◽  
Coastal Waters ◽  
Eastern Mediterranean ◽  
Propagation Speed ◽  
Surface Currents ◽  
Sampling Strategies ◽  
Open Sea ◽  
Levantine Basin ◽  
Transport Barriers

Abstract. A combined dataset of near real time multi-satellite observations and in situ measurements from a high-resolution survey, is used for characterizing physical-biogeochemical properties of a patch stretching from the coast to the open sea in the Levantine basin of the Eastern Mediterranean. Spatial analysis of the combined dataset indicates that the patch is a semi-enclosed system, bounded within the mixed layer and separated from ambient waters by transport barriers induced by horizontal stirring. As such, the patch is characterized by physical-biogeochemical properties that significantly differ from those of the waters surrounding it, with lower salinity, higher temperatures, higher concentrations of silicic acid and chlorophyll a, and higher abundance of Synechococcus and Picoeukaryotes cells. Based on estimates of patch dimensions (~ 40 km width and ~ 25 m depth) and propagation speed (~ 0.09 m s−1), the volume flux associated with the patch is found to be in the order of 0.1 Sv. Our observations suggest that horizontal stirring by surface currents is likely to have an important impact on the ultra-oligotrophic Levantine basin ecosystem, through (1) transport of nutrients and coastal derived material, and (2) formation of local, dynamically isolated, niches. In addition, this work provides a satellite-based framework for planning and executing high resolution sampling strategies in the interface between coast and the open sea.

Dissecting the Barotropic Transport in a High-resolution ocean model

2020 ◽  
Author(s):  
Martin Claus ◽  
Yuan Wang ◽  
Richard Greatbatch ◽  
Jinyu Sheng
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Spatial Scales ◽  
Ocean Model ◽  
Water Model ◽  
North Atlantic Current ◽  
The North ◽  
Circulation Patterns ◽  
Resolution Model ◽  
High Resolution Model

<p>We present a method to decompose the time mean vertically averaged transport, as simulated by an high-resolution ocean model, into its four dominant components. These components are driven by the gradient of potential energy per unit area (PE), the divergence of the flux of time mean momentum (MMF) and eddy momentum (EMF), and the wind stress. Since the local vorticity budget and the bathymetry are noisy and dominated by small spatial scales, a barotropic shallow water model is used as a filter to diagnose the respective transports instead of integrating along lines of constant f/H.<br>Applying this method to the output of a high-resolution model of the North Atlantic we find that PE is the most important driver, including the northwest corner. MMF is an important driver of transport around the Labrador Sea continental slope and, together with the EMF, it drives significant transport along the path of the Gulf Stream and North Atlantic current. Additionally, the circulation patterns driven by the EMF compares well with an estimate based on a satellite product. Hence, the presented method provides insights into the relative importance of the different dynamical processes that may drive barotropic transport in an ocean model. But it may also be used to isolate potential issues if a model misrepresents the barotropic transport.</p>

scholarly journals Comparison of extended and ensemble based Kalman filters with low and high resolution primitive equation ocean models

2005 ◽  
Vol 12 (5) ◽  
pp. 755-765 ◽  
Author(s):  
I. Hoteit ◽  
G. Korres ◽  
G. Triantafyllou
Keyword(s):  
High Resolution ◽  
Kalman Filters ◽  
Linear Analysis ◽  
Ocean Model ◽  
Primitive Equation ◽  
Gaussian Distributions ◽  
Resolution Model ◽  
High Resolution Model ◽  
Ocean Models ◽  
Very High

Abstract. Kalman filters are widely used for data assimilation into ocean models. The aim of this study is to discuss the relevance of these filters with high resolution ocean models. This was investigated through the comparison of two advanced Kalman filters: the singular evolutive extended Kalman (SEEK) filter and its ensemble-based variant, called SEIK filter. The two filters were implemented with the Princeton Ocean model (POM) considering a low spatial resolution configuration (Mediterranean sea model) and a very high one (Pagasitikos Gulf coastal model). It is shown that the two filters perform reasonably well when applied with the low resolution model. However, when the high resolution model is considered, the behavior of the SEEK filter seriously degrades because of strong model nonlinearities while the SEIK filter remains remarkably more stable. Based on the assumption of prior Gaussian distributions, the linear analysis step of the latter can still be improved though.

scholarly journals Assessment of one year of high-resolution operational forecasts for the southeastern Mediterranean shelf region in the MFSTEP project

2006 ◽  
Vol 3 (6) ◽  
pp. 2059-2085 ◽  
Author(s):  
S. Brenner ◽  
A. Murashkovsky ◽  
I. Gertman
Keyword(s):  
High Resolution ◽  
Initial Conditions ◽  
Forecast Model ◽  
Regional Model ◽  
Ocean Model ◽  
Operational Forecasts ◽  
Analysis Error ◽  
Ocean Forecasting ◽  
One Year ◽  
Shelf Region

Abstract. Within the framework of the MFSTEP project an operational ocean forecasting system for the Southeastern Mediterranean Sea has been implemented and evaluated through a series of preoperational tests and subsequently for one year of operational forecasts. The system is based on the Princeton Ocean Model (POM). The high-resolution shelf model is nested in a coarser resolution regional model, which is in turn nested in a coarser resolution full Mediterranean model. The respective grid sizes of the three models are 1.25, 3, and 6 km. Lateral boundary conditions are taken from the daily mean fields of the regional model while the surface forcing is taken from the hourly values of a regional atmospheric forecast model. When compared to satellite derived sea surface temperatures and the MFSTEP analysis fields, the high-resolution shelf model forecasts are significantly more skillful than the coarser model forecasts for the relevant domain. In the four-day forecasts, most of the error appears to be due to the analysis error inherent in the initial conditions. Future development of the system will therefore focus on improving the specification of the initial conditions.

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