The importance of altimeter and scatterometer data for ocean prediction

The prediction of ocean circulation using satellite altimeter data is discussed. Three classes of oceanic response to atmospheric forcing are outlined and examined. Storms, surface waves, eddies, and ocean currents were evaluated in terms of forecasting time requirements. Scatterometer and radiometer applications to ocean prediction are briefly reviewed

Sampling strategies and four-dimensional assimilation of altimetric data for ocean monitoring and prediction

Numerical experiments using simulated altimeter data were conducted in order to examine the assimilation of altimeter-derived sea surface heights into numerical ocean circulation models. A reduced-gravity, primitive equation circulation model of the Gulf of Mexico was utilized; the Gulf of Mexico was chosen because of its amenability to modeling and the ability of low vertical-mode models to reproduce the observed dynamical features of the Gulf circulation. The simulated data were obtained by flying an imaginary altimeter over the model ocean and sampling the model sea surface just as real altimeter would observe the true ocean. The data were used to initialize the numerical model and the subsequent forecast was compared to the true numerical solution. Results indicate that for a stationary, circular eddy, approximately three to four tracks (either ascending or descending) across the eddy are sufficient to ensure adequate spatial resolution

Turbulent Compressible Convection with Rotation

The effects of Coriolis forces on compressible convection are studied using three-dimensional numerical simulations carried out within a local modified f-plane model. The physics is simplified by considering a perfect gas occupying a rectilinear domain placed tangentially to a rotating sphere at various latitudes, through which a destabilizing heat flux is driven. The resulting convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers, evaluating conditions where the influence of rotation is both weak and strong. Given the computational demands of these high-resolution simulations, the parameter space is explored sparsely to ascertain the differences between laminar and turbulent rotating convection. The first paper in this series examines the effects of rotation on the flow structure within the convection, its evolution, and some consequences for mixing. Subsequent papers consider the large-scale mean shear flows that are generated by the convection, and the effects of rotation on the convective energetics and transport properties. It is found here that the structure of rotating turbulent convection is similar to earlier nonrotating studies, with a laminar, cellular surface network disguising a fully turbulent interior punctuated by vertically coherent structures. However, the temporal signature of the surface flows is modified by inertial motions to yield new cellular evolution patterns and an overall increase in the mobility of the network. The turbulent convection contains vortex tubes of many scales, including large-scale coherent structures spanning the full vertical extent of the domain involving multiple density scale heights. Remarkably, such structures align with the rotation vector via the influence of Coriolis forces on turbulent motions, in contrast with the zonal tilting of streamlines found in laminar flows. Such novel turbulent mechanisms alter the correlations which drive mean shearing flows and affect the convective transport properties. In contrast to this large-scale anisotropy, small-scale vortex tubes at greater depths are randomly orientated by the rotational mixing of momentum, leading to an increased degree of isotropy on the medium to small scales of motion there. Rotation also influences the thermodynamic mixing properties of the convection. In particular, interaction of the larger coherent vortices causes a loss of correlation between the vertical velocity and the temperature leaving a mean stratification which is not isentropic

On the Currents and Transports Connected With the Atlantic Meridional Overturning Circulation in the Subpolar North Atlantic

Results from an interannually forced, 0.08 degrees eddy-resolving simulation based on the Hybrid Coordinate Ocean Model, in conjunction with a small but well-determined transport database, are used to investigate the currents and transports associated with the Atlantic meridional overturning circulation (AMOC) in the subpolar North Atlantic (SPNA). The model results yield a consistent warming in the western SPNA since the early 1990s, along with mean transports similar to those observed for the trans-basin AMOC across the World Ocean Circulation Experiment hydrographic section AR19 (16.4 Sv) and boundary currents at the exit of the Labrador Sea near 53 degrees N (39.0 Sv) and east of the Grand Banks near 43 degrees N (15.9 Sv). Over a 34 year integration, the model-determined AMOC across the AR19 section and the western boundary current near 53 degrees N both exhibit no systematic trend but some long-term (interannual and longer) variabilities, including a decadal transport variation of 3-4 Sv from relatively high in the 1990s to low in the 2000s. The decadal variability of the model boundary current transport near 53 degrees N lags the observed winter time North Atlantic Oscillation index by about 2 years and leads the model AMOC across the AR19 section by about 1 year. The model results also show that the long-term variabilities are low compared to those on shorter time scales. Thus, rapid sampling of the current over long time intervals is required to filter out high-frequency variabilities in order to determine the lower frequency variabilities of interest. Citation: Xu, X., H. E. Hurlburt, W. J. Schmitz Jr., R. Zantopp, J. Fischer, and P. J. Hogan (2013), On the currents and transports connected with the atlantic meridional overturning circulation in the subpolar North Atlantic, J. Geophys. Res. Oceans, 118, 502-516, doi:10.1002/jgrc.20065

GODAE systems in operation

During the last 15 years, operational oceanography systems have been developed in several countries around the world. These developments have been fostered primarily by the Global Ocean Data Assimilation Experiment (GODAE), which coordinated these activities, encouraged partnerships, and facilitated constructive competition. This multinational coordination has been very beneficial for the development of operational oceanography. Today, several systems provide routine, real-time ocean analysis, forecast, and reanalysis products. These systems are based on (1) state-of-the-art Ocean General Circulation Model (OGCM) configurations, either global or regional (basin-scale), with resolutions that range from coarse to eddy-resolving, and (2) data assimilation techniques ranging from analysis correction to advanced three- or four-dimensional variational schemes. These systems assimilate altimeter sea level anomalies, sea surface temperature data, and in situ profiles of temperature and salinity, including Argo data. Some systems have implemented downscaling capacities, which consist of embedding higher-resolution local systems in global and basin-scale models (through open boundary exchange of data), especially in coastal regions, where small scale-phenomena are important, and also increasing the spatial resolution for these regional/coastal systems to be able to resolve smaller scales (so-called downscaling). Others have implemented coupling with the atmosphere and/or sea ice. This paper provides a short review of these operational GODAE systems.Published76-914.6. Oceanografia operativa per la valutazione dei rischi in aree marineN/A or not JCRope

GODAE systems in operation

During the last 15 years, operational oceanography systems have emerged in several countries around the world. This emergence has been largely fostered by the GODAE experiment, during which each nation engaged in this activity have organised partnership and constructive competition. This trans-national coordination was very beneficial for the development of operational oceanography, leading to economies of scales and more targeted actions. Today, several systems provide routine real-time ocean analysis and forecast and/or reanalysis products. They are all based on (i) state-of-the-art primitive equation baroclinic Ocean General Circulation Model (OGCM) configurations, either global or regional (basin-scale), with resolutions that range from coarse to eddy resolving and (ii) data assimilation techniques whose complexity ranges from simple analysis correction to advanced 4D variational schemes. They assimilate altimeter sea level anomalies, remotely sensed SST such as GHRSST products and in situ profiles of T and S, including ARGO. Some systems have implemented downscaling capacities in specific regions of interest including shelf/coastal seas. Some also have implemented coupling with the atmosphere and/or the prognostic sea ice in polar regions. They are the GODAE system in operation. They are reviewed in this paper. The GODAE system discussed here include: (1) BLUElink OceanMAPS, (2) C-NOOFS, , (3) ECCO, (4) FOAM, (5) HYCOM/NCODA, (6) MERCATOR, (7) MFS, (8) MOVE/MRI.COM, (9) NLOM/NCOM, (10) NMEFC, (11) RTOFS and (12) TOPAZ.SubmittedNice, France3.11. Oceanografia Operativaope

GODAE systems in operation

During the last 15 years, operational oceanography systems have been developed in several countries around the world. These developments have been fostered primarily by the Global Ocean Data Assimilation Experiment (GODAE), which coordinated these activities, encouraged partnerships, and facilitated constructive competition. This multinational coordination has been very beneficial for the development of operational oceanography. Today, several systems provide routine, real-time ocean analysis, forecast, and reanalysis products. These systems are based on (1) state-of-the-art Ocean General Circulation Model (OGCM) configurations, either global or regional (basin-scale), with resolutions that range from coarse to eddy-resolving, and (2) data assimilation techniques ranging from analysis correction to advanced three- or four-dimensional variational schemes. These systems assimilate altimeter sea level anomalies, sea surface temperature data, and in situ profiles of temperature and salinity, including Argo data. Some systems have implemented downscaling capacities, which consist of embedding higher-resolution local systems in global and basin-scale models (through open boundary exchange of data), especially in coastal regions, where small scale-phenomena are important, and also increasing the spatial resolution for these regional/coastal systems to be able to resolve smaller scales (so-called downscaling). Others have implemented coupling with the atmosphere and/or sea ice. This paper provides a short review of these operational GODAE systems

GODAE systems in operation

During the last 15 years, operational oceanography systems have emerged in several countries around the world. This emergence has been largely fostered by the GODAE experiment, during which each nation engaged in this activity have organised partnership and constructive competition. This trans-national coordination was very beneficial for the development of operational oceanography, leading to economies of scales and more targeted actions. Today, several systems provide routine real-time ocean analysis and forecast and/or reanalysis products. They are all based on (i) state-of-the-art primitive equation baroclinic Ocean General Circulation Model (OGCM) configurations, either global or regional (basin-scale), with resolutions that range from coarse to eddy resolving and (ii) data assimilation techniques whose complexity ranges from simple analysis correction to advanced 4D variational schemes. They assimilate altimeter sea level anomalies, remotely sensed SST such as GHRSST products and in situ profiles of T and S, including ARGO. Some systems have implemented downscaling capacities in specific regions of interest including shelf/coastal seas. Some also have implemented coupling with the atmosphere and/or the prognostic sea ice in polar regions. They are the GODAE system in operation. They are reviewed in this paper. The GODAE system discussed here include: (1) BLUElink OceanMAPS, (2) C-NOOFS, , (3) ECCO, (4) FOAM, (5) HYCOM/NCODA, (6) MERCATOR, (7) MFS, (8) MOVE/MRI.COM, (9) NLOM/NCOM, (10) NMEFC, (11) RTOFS and (12) TOPAZ