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See detailReconstruction of Missing Satellite Total Suspended Matter Data over the Southern North Sea and English Channel using Empirical Orthogonal Function Decomposition of Satellite Imagery and Hydrodynamical Modelling
Sirjacobs, Damien ULiege; Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege et al

Poster (2008, October)

Optical remote sensing data archives generally have many gaps caused by clouds or other retrieval problems. However, for the light forcing of ecosystem models continuous fields are required. For ... [more ▼]

Optical remote sensing data archives generally have many gaps caused by clouds or other retrieval problems. However, for the light forcing of ecosystem models continuous fields are required. For parameters exhibiting strong spatial and temporal correlations for regions of similar dynamics or from day to day, the missing data can be estimated by use of statistical techniques. In this context, the Data Interpolation with Empirical Orthogonal Functions (DINEOF) method is used for reconstruction of complete space-time information for surface total suspended matter (TSM) and chlorophyll a from a 5-year archive of MODIS and MERIS products over the Southern North Sea and English Channel. The DINEOF univariate methodology has been previously demonstrated for Mediterranean sea surface temperature data (Alvera-Azcarate et al., 2005, Beckers et al., 2006). Alvera-Azcarate et al (2007) showed that SST reconstructions could be improved by using a multivariate approach in which SST, chlorophyll and wind fields were taken into account together for the analyses. Here, TSM images will be used in combination with information from the COHERENS hydrodynamical model to provide a complete and continuous estimate of surface TSM for the Southern North Sea throughout the period 2003-2005. In addition to the remotely sensed TSM, the DINEOF multivariate analysis will consider wind fields, depth integrated currents, surface elevations and bottom stresses. Reconstucted images are compared with the original incomplete images. Validation of the method is achieved by estimation of information removed from the training data by exclusion of entire images and by addition of artificial clouds. The data reconstruction technique has further applications in the processing and quality control of optical remote sensing data. Perspectives will be outlined for improving the quality control of retrieved parameters and for the improvement of retrievals by adding statistical information to the conventional spectral processing. References: Alvera-Azcarate, A., Barth, A., Rixen, M., and Beckers, J.-M.: Reconstruction of incomplete oceanographic data sets using Empirical Orthogonal Functions. Application to the Adriatic Sea, Ocean Modelling, 9, 325–346, 2005. Alvera-Azcarate, A., Barth, A., Beckers, J. M., and Weisberg, R. H.: Multivariate Reconstruction of Missing Data in Sea Surface Temperature, Chlorophyll and Wind Satellite Fields, Journal of Geophysical Research, 112, C03008, doi:10.1029/2006JC003660, 2007. Beckers J.-M., A. Barth & A. Alvera-Azcarate, DINEOF reconstruction of clouded images including error maps. Application to the Sea-Surface Temperature around Corsican Island, Ocean Sciences, 2: 183–199, 2006. [less ▲]

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See detailCloud filling of total suspended matter, chlorophyll and sea surface temperature remote sensing products by the Data Interpolation with Empirical Orthogonal Functions methodology, application to the BELCOLOUR-1 database
Sirjacobs, Damien ULiege; Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege et al

in ESA Special Publication SP666 (2008, September)

Space-time filling of the gaps in satellite data archives is an important step for the improvement of various marine ecosystem studies. The Data Interpolation with Empirical Orthogonal Functions ... [more ▼]

Space-time filling of the gaps in satellite data archives is an important step for the improvement of various marine ecosystem studies. The Data Interpolation with Empirical Orthogonal Functions methodology (DINEOF) allows calculating missing data in geophysical datasets without requiring a priori knowledge about statistics of the full data set [1]. It was successfully applied to SST reconstructions as in [1] and [2]. Here, the DINEOF reconstruction method is applied to surface chlorophyll a (CHL), total suspended matter (TSM) and sea surface temperature (SST) data over the Southern North Sea and English Channel obtained from the BELCOLOUR archive. 1. Beckers, J.-M. and Rixen, M. (2003). EOF Calculations and Data Filling from Incomplete Oceanographic Datasets. Journal of Atmospheric and Oceanic Technology, 20:18391856. 2. Alvera-Azcárate, A., Barth, A., Rixen, M. and Beckers, J.-M. (2005). Reconstruction of incomplete oceanographic data sets using Empirical Orthogonal Functions. Application to the Adriatic Sea surface temperature. Ocean Modelling, 9:325–346. [less ▲]

Detailed reference viewed: 81 (10 ULiège)
See detailREconstruction of COLOUR scenes
Sirjacobs, Damien ULiege; Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege et al

Poster (2008, February 12)

Detailed reference viewed: 24 (2 ULiège)
See detailDownscaling of the global HYCOM to the Cariaco basin (Venezuela) using ROMS
Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege; Weisberg, R. H.

Conference (2008)

A high-resolution (1/60 degree), three-dimensional numerical circulation model of the Cariaco basin (Venezuela) is constructed by nesting the Regional Ocean Modeling System (ROMS) in the 1/12 degree ... [more ▼]

A high-resolution (1/60 degree), three-dimensional numerical circulation model of the Cariaco basin (Venezuela) is constructed by nesting the Regional Ocean Modeling System (ROMS) in the 1/12 degree global Hybrid Coordinate Ocean Model (HYCOM). The Cariaco basin is a semi-enclosed trench located along the coast of Venezuela. Its maximum depth is about 1400 m, and it is connected to the open ocean by two shallow passages: the Centinela channel in the northwest (146 m depth) and the Tortuga channel in the northeast (135 m depth). The main objective of this work is to improve our knowledge of the Cariaco basin dynamics, and to understand how the basin is influenced by the Caribbean Sea. The nesting of the Cariaco model in HYCOM is therefore crucial for these analyses. First, the annual cycle of the basin is described, using the results from a 2004 hindcast. Then, two modes of interaction between the basin and the open ocean are studied: (i) the meanders and eddies that travel westward with the Caribbean Current, and (ii) a subsurface eastward current that flows along the South America north coast. The ventilation of the basin through its channels is analyzed by studying the annual variations of the thermocline depth in the basin channels. In addition to the improved knowledge of the Cariaco basin circulation, which can help to better understand the climate of the past through paleoceanographic studies, this work is also an example of the feasibility of one of the objectives of GODAE: downscaling from a large-scale model to a regional model. In particular, the nesting ratio of 5 used in this work (from 9 km down to 1.82 km) demonstrates that a high-resolution model can be successfully nested in HYCOM. [less ▲]

Detailed reference viewed: 68 (3 ULiège)
See detailUsing monovariate and multivariate EOFs to reconstruct missing data with DINEOF
Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege; Sirjacobs, Damien ULiege et al

Conference (2008)

DINEOF (Data Interpolating Empirical Orthogonal Functions) is an EOF-based method to reconstruct missing data in geophysical data sets. DINEOF can be used to reconstruct monovariate data sets (as sea ... [more ▼]

DINEOF (Data Interpolating Empirical Orthogonal Functions) is an EOF-based method to reconstruct missing data in geophysical data sets. DINEOF can be used to reconstruct monovariate data sets (as sea surface temperature (SST), chlorophyll, etc), and multivariate data sets with little increase in complexity. For multivariate reconstructions, extended EOFs are used, which take into account the interrelationships between related variables to infer data at missing locations. Spatial maps of the standard deviation of the reconstruction error can be also calculated. In the past, DINEOF has been compared to Optimal Interpolation (OI) techniques for the Adriatic Sea SST. The results showed that DINEOF was faster than OI, making it very suitable for operational applications. DINEOF was also more accurate when compared to in situ data. Another advantage of DINEOF is that there is no need for a priori knowledge of the statistics of the reconstructed data set (such as covariance or correlation length), thus reducing the subjectivity of the analysis. DINEOF has been successfully used to reconstruct a large variety of domains over the world ocean, mostly at the regional scale. In addition to an overview of the technique's capabilities, limitations and future developments, recent work aimed to improve the quality of the reconstructions at the global and local scales will be presented. [less ▲]

Detailed reference viewed: 55 (4 ULiège)
See detailA Nested Model of the West Florida Shelf: Assimilation of High-Frequency Radar Currents and study of Loop Current generated flow
Barth, Alexander ULiege; Alvera Azcarate, Aïda ULiege; Zheng, L. et al

Conference (2008)

High-Frequency Radar Currents are assimilated in a West Florida Shelf (WFS) model based on the Regional Ocean Model System (ROMS) which is nested in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) to ... [more ▼]

High-Frequency Radar Currents are assimilated in a West Florida Shelf (WFS) model based on the Regional Ocean Model System (ROMS) which is nested in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) to include both local and deep-ocean forcing, particularly the Gulf of Mexico Loop Current (LC). An ensemble simulation of the WFS ROMS model is carried out under different wind forcings in order to estimate the error covariance of the model state vector and the covariance between ocean currents and winds. Radial currents measured by HF-Radar antennas near St. Petersburg and Venice, FL, are assimilated using this ensemble-based error covariance. Different assimilation techniques using a time-average ensemble, a filter to reduce surface-gravity waves and an extended state vector including wind stress were tested. Results of WFS ROMS model assimilating surface currents show an improvement of the model currents not only at the surface but also at depth. The LC is a highly unstable current which generates large anticyclones traveling to the West but also a series of smaller anticyclones and filaments moving to the East and affecting the West Florida shelf. An additional tracer is included in the model simulation to track the presence of LC water. With this tracer, the total amount of LC water reaching the shelf and its mechanism is studied. [less ▲]

Detailed reference viewed: 51 (1 ULiège)
See detailThermocline characterization on modeled and observed temperature profiles: a technique for model error evaluation
Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege; Beckers, Jean-Marie ULiege

Conference (2008)

The thermocline position in the water column is an important variable in hydrodynamic modeling. Its characterization allows to verify the model accuracy, and analyze the parameter choice made by the ... [more ▼]

The thermocline position in the water column is an important variable in hydrodynamic modeling. Its characterization allows to verify the model accuracy, and analyze the parameter choice made by the modeler, such as the choice of the turbulence closure. A correct representation of the surface ocean boundary layer is also very important in order to correctly represent the air-sea exchanges. Moreover, coupled physicalbiological models require a good representation of the thermocline position, in order to correctly represent the population dynamics at the surface layers. We present a technique to calculate the parameters of the thermocline: depth, width and temperature. These are calculated by a least-squares fitting of individual temperature profiles (from model and observations) to a sigmoid function. The residual is also obtained, giving an estimate of the goodness of the fit. The parameters calculated allow for a comparison of the model thermocline to observations. Our approach consists in comparing the model thermocline depth, width and temperature to observations. By examining separately the accuracy of the model thermocline depth and temperature, we gain insight in the processes that need correction in the model. For example, if the model thermocline is too deep compared to observations, or the width of the thermocline is incorrect, mixing parameters and surface momentum fluxes should be revised. However, if the depth is well represented but the temperature is incorrect, the surface heat fluxes may be the source of the error. By simply comparing model and observed temperature profiles we are not able to differentiate between error sources. The technique presented here stands therefore as a useful method for model evaluation. [less ▲]

Detailed reference viewed: 66 (3 ULiège)
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See detailDINEOF univariate reconstruction of missing satellite data from the North Sea Belcolour-1 database.
Sirjacobs, Damien ULiege; Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege et al

Poster (2008)

The Belcolour-1 database holds more than 4 years of uniformly resampled MERIS chlorophyll (CHL), total suspended matter (TSM), MODIS-AQUA CHL, TSM and sea surface temperature (SST) over the North Sea. A ... [more ▼]

The Belcolour-1 database holds more than 4 years of uniformly resampled MERIS chlorophyll (CHL), total suspended matter (TSM), MODIS-AQUA CHL, TSM and sea surface temperature (SST) over the North Sea. A first step of the RECOLOUR* project consists in the univariate reconstruction of missing data with the DINEOF method (Data Interpolating Empirical Orthogonal Functions). In particular, the DINEOF treatment of MERIS CHL and TSM images available for the year 2003 allowed an efficient synthesis of the coherent modes of variability existing at the scale of the whole North Sea. For both parameters, 4 modes were retained by general cross validation as an optimum for the reconstruction of missing data. For CHL, the first spatial mode shows the high influence of coastal nutrients outputs (mainly continental estuaries and diffused coastal sources) and the lower concentration in the well stratified central and northern part of the North Sea compared to the southern bight and the eastern English Channel. The spatial trends described by the first mode are permanent features during the year, although slightly enhanced during the summer and reduced during winter. The second spatial mode correspond to the main algal blooming events (spring and autumn) with increased concentrations in the whole southern bight of the north sea, around the Isle of Wight and in frontal alike structure north-west from Denmark. The third Eofs describes well the dynamics of an early phytoplankton bloom occurring in march along the Norwegian coast, where a strong stratification induced by an output of cold water from Baltic Sea provides good light conditions to phytoplankton. Concerning TSM, the first spatial mode shows the dominant influence of large estuaries and of resuspension from shallow coastal sedimental plains. The patterns suggest a general transport of sediments from south-east England up to the northern Dutch coastal waters, as a clear distinction between the stratified northern part and the well mixed and charged southern and German bights. Although these trends are permanent during the year, the range of the spatial variations are slightly reduced during the summer, following the reduction of resuspension, of total sediment outputed by rivers and of advection along continental coasts. The second mode shows a clear seasonal signal. The winter influence of the second spatial mode can be understood as general sediment enrichment due to higher resuspension, but a clear influence of intense winter terrestrial water outflows leading to lower sediment concentration in the plumes then in the surrounding waters. This is clear for the Elbe river discharge, the whole natural part of the Wadden Sea and the Seine river plume. The Scheelde and Thames rather seems to be just neutralizing the seasonal TSM resuspension signal. The Rhine river discharge seems to make exception as no influence is detected in the second spatial mode. During summer, the contribution of the second EOF is reversed with a general reduction of suspended matter concentration in most part of the area but some local sediment enrichment at specific river discharges. Original MERIS CHL and TSM images were filled and reconstructions were produced at a daily interval based on a linear interpolation of the temporal modes. From this, weekly averages could be calculated at stations such as the turbidity maximum of the Scheelde river plume, showing the onset of the spring bloom co-occurring with a period characterised both by the TSM seasonal reduction and by important TSM temporal variability. [less ▲]

Detailed reference viewed: 33 (1 ULiège)
See detailAssimilation of High-Frequency Radar Currents in a Nested Model of the West Florida Shelf
Barth, Alexander ULiege; Alvera Azcarate, Aïda ULiege; Weisberg, R. H.

Conference (2007)

High-frequency radar currents are assimilated in a West Florida Shelf (WFS) model based on the Regional Ocean Model System (ROMS), which is nested in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) for ... [more ▼]

High-frequency radar currents are assimilated in a West Florida Shelf (WFS) model based on the Regional Ocean Model System (ROMS), which is nested in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) for the purpose of including both local and deep-ocean forcing, particularly the Gulf of Mexico Loop Current. Tides are not included in this model. An ensemble simulation of the WFS model is carried out under different wind-forcings in order to estimate the error covariance of the model state vector and the covariance between ocean currents and winds. Radial currents measured by high-frequency radar antennas near Saint Petersburg and Venice, Florida, USA, are assimilated using this ensemble-based error covariance. Different assimilation techniques using a time-average ensemble, a filter to reduce surface-gravity waves and an extended state vector including wind stress were tested. Results of the WFS model assimilating surface currents show an improvement of the model currents not only at the surface but also at depth. [less ▲]

Detailed reference viewed: 47 (3 ULiège)
See detailA West Florida Shelf ROMS Nested into HYCOM: Ensemble-based Assimilation of HF-Radar Surface Currents and a 2005 Red Tide Case Study with Simulated Drifters
Barth, Alexander ULiege; Alvera Azcarate, Aïda ULiege; Weisberg, R. H.

Conference (2007)

A West Florida Shelf (WFS) model is constructed by nesting the Regional Ocean Model System (ROMS) in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) to include both local and deep-ocean forcing ... [more ▼]

A West Florida Shelf (WFS) model is constructed by nesting the Regional Ocean Model System (ROMS) in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) to include both local and deep-ocean forcing, particularly the Gulf of Mexico Loop Current (LC). Hindcast experiments from 2004 to 2006 are presented and compared to observed temperature (moorings and BSOP profiling floats), ADCP velocity time series and HF-Radar surface currents. Two different mixing schemes (Mellor Yamada level 2.5 and K-Profile Parameterization, KPP) are tested and the importance of the vertical resolution for mixing is addressed. The model results of those different configurations are compared to temperature observations on the shelf. Results obtained with the Mellor Yamada scheme are closer to observations during winter (negative buoyancy flux and strong winds) while in summer (positive buoyancy flux and in general weaker wind) the KPP scheme produces more realistic results. Given the present HYCOM configuration we assessed the benefit of nesting ROMS in HYCOM compared to nesting ROMS in climatology. The model solutions on the shelf were compared to various in situ data. The model performed best when using the HYCOM boundary values. Simulated trajectories for drifters deployed off Tampa Bay and Sarasota were used to address the evolution of Karenia brevis concentrations during the 2005 red tide. Near surface drifters were advected offshore, whereas drifters deployed in the bottom Ekman layer matched the subsequently observed Karenia brevis distributions, showing the importance of the 3D structure of coastal ocean currents for red tide on the WFS. As a first attempt at assimilating CODAR surface currents we used an ensemble simulation carried out under different wind forcings to estimate the error covariance of the model state vector and the covariance between the ocean currents and the wind. Improvements were obtained for the modeled currents, not only at the surface, but also at depth. [less ▲]

Detailed reference viewed: 49 (4 ULiège)
See detailA Nested Model of the Cariaco Basin: Study of the Hydrography and Interactions with the Open Ocean
Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege; Virmani, J. I. et al

Conference (2007)

The circulation of the Cariaco Basin (Venezuela) is modeled using the Regional Ocean Model System (ROMS) nested in the global 1/12 degree Hybrid Coordinate Ocean Model (HYCOM). The objective of this work ... [more ▼]

The circulation of the Cariaco Basin (Venezuela) is modeled using the Regional Ocean Model System (ROMS) nested in the global 1/12 degree Hybrid Coordinate Ocean Model (HYCOM). The objective of this work is to obtain a better understanding of the Cariaco Basin circulation by studying the processes that link the basin with the Caribbean Sea. To our knowledge, this is the first attempt to model the circulation in the Cariaco Basin with a nested high resolution hydrodynamical model. In particular, we examined the interaction of the Cariaco Basin with the large-scale, open-ocean processes, as the westward Caribbean Current and the eastward subsurface counter-current flowing along the South America Caribbean coast. These two current systems connect the Cariaco Basin with the Caribbean Sea waters, and therefore are directly related to the ventilation of the basin. By studying the kinematics and dynamics of the Cariaco Basin we anticipate gaining a better understanding on how the past conditions affected the basin characteristics and hence the geological records obtained from the basin sediments. We will report on several years of observations from the continuous monitoring of currents within the basin, plus analyses of year-long model runs that provide a basin-wide, three-dimensional context for the circulation. [less ▲]

Detailed reference viewed: 15 (1 ULiège)
See detailIAS Mesoscale Surface Circulation Observed Through Satellite Altimetry and its Influence in a Small Scale, Coastal Domain, Studied with a ROMS Model of the Cariaco Basin
Alvera Azcarate, Aïda ULiege; Barth, Alexander ULiege; Virmani, J. I. et al

Conference (2007)

The Intra-Americas Sea (IAS) surface circulation is characterized by large scale currents. The Caribbean current, which originates in the Lesser Antilles, travels westwards through the Caribbean Sea and ... [more ▼]

The Intra-Americas Sea (IAS) surface circulation is characterized by large scale currents. The Caribbean current, which originates in the Lesser Antilles, travels westwards through the Caribbean Sea and eastern Mexico and passes through the Gulf of Mexico to finally form the Gulf Stream. This complex system of currents is also characterized by a high mesoscale variability, such as eddies and meanders. The objectives of this work are twofold: first, the multi-scale surface circulation of the IAS is described using satellite altimetry. The topographic influence of the different basins forming the IAS, the characteristic time and spatial scales, and the time variability of the surface circulation will be addressed. The second objective is to analyze the influence of this large scale circulation on a small scale coastal domain with a ROMS-based model of the Cariaco basin (Venezuela). Cariaco is a deep (1400 m), semi-enclosed basin connected to the open ocean by two shallow channels (Tortuga and Centinela Channels). Its connection with the open sea, and therefore the ventilation of the basin, occurs in the surface layers. The Cariaco ROMS model will be used to study the exchanges of mass, heat and salt through the channels. A 1/60 degree ROMS model nested in the global 1/12 degree HYCOM model from the Naval Research Laboratory will be used for this study. In addition, a series of observations (satellite altimetry and in situ temperature, salinity and velocity data), will be used to assess the influence of the Caribbean circulation on the basin. [less ▲]

Detailed reference viewed: 30 (2 ULiège)
See detailError analysis of a high-resolution physical model of the Mediterranean Sea
Vandenbulcke, Luc ULiege; Barth, Alexander ULiege; Alvera Azcarate, Aïda ULiege et al

Conference (2007)

We analyze the errors that are inevitably associated to hydrodynamic models, in a realistic case. The error of the GHER model in the Mediterranean Sea has already been studied in e.g. Beckers et al. (2000 ... [more ▼]

We analyze the errors that are inevitably associated to hydrodynamic models, in a realistic case. The error of the GHER model in the Mediterranean Sea has already been studied in e.g. Beckers et al. (2000) by comparing it with other primitive equation models, or in Alvera (2004) by comparing the model with observations and with the climatology, using usual statistical methods and also wavelet decompositions. In this study, we rather study the sensitivity of the model to various variables using an ensemble of models. We chose a relatively high resolution, 1/16°, corresponding to the resolution now used in operational OGCMs covering the Mediterranean, such as the MFS system (http://www.bo.ingv.it/mfs). We explain how we generated an ensemble of model simulations, where various more-or-less well known inputs are allowed to vary according to the uncertainty affecting them. Statistics calculated on this ensemble are, in fact, the response of the non-linear hydrodynamic system to errors on the forcing terms. When those statistics are calculated at a certain timestep, they allow us to provide a spatial analysis of the model error; statistics calculated over the time dimension will show whether errors are intensified by the system, or rather disappear. The model error is interesting as such. However, it can also be used for different purposes. For example, it allows using data assimilation techniques without needing the usual assumptions of reduced-rank Kalman Filters. It also allows studying the sensitivity of coupled model (biological, oil spill, search-and-rescue, …) to physical forcings. [less ▲]

Detailed reference viewed: 25 (2 ULiège)
See detailData assimilation as a tool for upscaling
Vandenbulcke, Luc ULiege; Barth, Alexander ULiege; Ben Bouallegue, Z. et al

Conference (2006, April)

In ocean and atmospheric sciences, grid nesting is a common procedure in order to achieve (very) high resolution model outputs in regions of particular interest, at an acceptable computational cost ... [more ▼]

In ocean and atmospheric sciences, grid nesting is a common procedure in order to achieve (very) high resolution model outputs in regions of particular interest, at an acceptable computational cost. Nesting of grids can be passive (one-way nesting) or active (two-way nesting, with feedback from the high resolution to the low resolution grid). The benefits of active nesting have been shown multiple times in the litterature (see e.g. [1]). The positive effect of the feedback is visible inside the nested grid, but also outside of it, as corrections are advected with the flow. It must be noted however that in many operationnal implementations, only passive nesting is used, usually because active nesting requires too much data exchange between models, which should then wait for each other during their run. Data assimilation techniques are also widespread in oceanic and atmospheric models. They are usually applied in order to merge observations in models, but also e.g. to merge different outputs from ensemble runs of a model, to merge outputs from different models, or to replace downscaling between nested grids (see [3]). In our work, we present an alternative to active nesting (for implementations currently using passive nesting). First, the low-resolution model is run, followed by the local model. Afterwards, the low-resolution model is run once more, assimilating outputs from the local model as pseudo-data. The benefits of this approach over simple passive nesting are shown using a twin experiment. The GHER model (see [2]) is configured with a 0.25 resolution of the Mediterranean Sea, and with a 0.05 resoluion of the North-Western part; a twin experiment is then set. The reference run uses full two-way nesting, another run uses one-way nesting, and in a third run the assimilation procedure described above is implemented.Conclusions from this experiment are that our "upscaling" has positive impacts on the forecasts, provided a fair amount of EOFs is used during (reduced-rank) assimilation cycles. Finally, the set-up of ongoing work to implement our upscaling procedure in a realistic, operationnal system (the MFS system) is presented. [less ▲]

Detailed reference viewed: 46 (2 ULiège)
See detailA baroclinic, regional West Florida Shelf model nested in a 1/12 degree North Atlantic HYCOM model, inclusive of tides
Barth, Alexander ULiege; Alvera Azcarate, Aïda ULiege; Weisberg, R. H.

Conference (2006)

A West Florida Shelf (WFS) model based on the Regional Ocean Model System (ROMS) is nested in the 1/12° North Atlantic Hybrid Coordinate Ocean Model (NAT HYCOM). The nesting procedure is based on a flow ... [more ▼]

A West Florida Shelf (WFS) model based on the Regional Ocean Model System (ROMS) is nested in the 1/12° North Atlantic Hybrid Coordinate Ocean Model (NAT HYCOM). The nesting procedure is based on a flow relaxation scheme, and the model implementation is tested against in situ data over a one-year hindcast simulation. While the focus of NAT HYCOM is the large-scale circulation, the aim of this study is to show that the NAT HYCOM results can be improved by nesting a regional model with increased resolution. Results are compared qualitatively to sea surface height and quantitatively to in situ temperature and velocity measurements on the shelf. The nesting of a regional model improves the performance on the shelf. The inclusion of tides is a new addition, and preliminary results are shown. [less ▲]

Detailed reference viewed: 23 (3 ULiège)