Description: in the file

Description: Published

Description: 22-25

Description: open

Description: Operational evolution of global and regional ocean forecasting systems has been extremely significant in recent years. GODAE (Global Ocean Data Assimilation Experiment) Oceanview supports the national research groups providing them with coordination and sharing expertise among the partners. Several systems have been set up and developed pre-operationally and the majority of these are now fully operational; at the present time, they provide medium- and long-term forecasts of the most relevant ocean physical variables. These systems are based on ocean general circulation models (OGCMs) and data assimilation techniques that are able to correct the model with the information inferred from different types of observations. A few systems also incorporate a biogeochemical component coupled with the physical system while others are based on coupled ocean-wave-ice-atmosphere models. The products are routinely validated with observations in order to assess their quality. Data and products implementation and organization, as well as service for the users has been well tried and tested and most of the products are now available  to the users. The interaction with different users is an important factor in the development process. This paper provides a synthetic overview of the GODAE Oceanview prediction systems.

Description: Published

Description: s201-s220

Description: 4A. Clima e Oceani

Description: JCR Journal

Description: open

Description: conductivity, is a key control on the thermal state of near surface permafrost. At the same time, accurately estimating the seasonal snow cycle at the kilometre scale is a considerable hydrometeorological challenge. Consequently, snow represents a major source of uncertainty in permafrost models. To constrain this snow induced uncertainty we propose a new ensemblebased snow data assimilation framework (ESDA) for fine scale snow state estimation that fuses a simple subgrid snow model and fine scale satellite-based surface albedo retrievals using the ensemble Kalman filter (EnKF; reviewed in Evensen [2009]). The potential of ESDA is demonstrated for the Bayelva catchment near Ny Åelsund (Svalbard, Norway) where independent ground-based observations of snow cover and the near surface ground thermal state were available to perform validation. On the modeling side of ESDA we adopt the subgrid snow distribution model (SSNOWD; see Liston [2004]) to estimate the snow water equivalent depth distribution, snow cover fraction and surface albedo at the grid scale (1 km). These model runs are forced by melt and net precipitation rates based on the energy and water balance derived from the meteorological fields provided by a (3 km resolution) Weather Research and Forecasting (WRF) model run. For observations our system makes combined use of two relatively new high level products: frequently available coarser scale (500 m) albedo retrievals from MODIS (MCD43A version 6) and intermittently available finer scale (30 m) albedos derived from Landsat8 surface reflectance retrievals. In the last step of the framework we apply the EnKF; a robust sequential data assimilation method that yields the optimal estimate of a system state based on the combined information from model results and observations, both of which are uncertain, provided a set of assumptions hold (see Evensen [2009]). The EnKF has been successfully implemented for a range of applications in numerous fields including oceanography, meteorology, hydrology, mining and reservoir geophysics, although to our knowledge this is the first time it is being applied directly to permafrost modeling. Simply stated an ensemble (a set) of model realizations, in this case capturing uncertainties in the meteorological forcing, are propagated forward in time and sequentially updated by the observations whenever these are available. The magnitude of the updates depends on the deviation of the model realizations from the observations as well as the respective uncertainties. Thereby, the result of the EnKF is expressed in terms of an ensemble of corrected model states, where the ensemble mean is interpreted as the most likely estimate and the ensemble spread is a measure of the uncertainty. Our results are promising; the evolution of the ensemble mean estimated snow cover using ESDA at Bayelva is shown to be much closer to the ground-truth, as observed by an independent automatic camera system, than that of the open-loop (no assimilation) estimate. Finally, we incorporate ESDA into the recently developed CryoGrid3 surface energy-balance driven permafrost model described in Westermann et al. [2016]. The results, with and without ESDA, are compared to in situ measurements from an array of randomly distributed ground surface temperature measurements within the modeled grid cell. A significant improvement in the skill of the model at capturing the near-surface ground thermal state is demonstrated, particularly in the ablation season. Thus, ESDA provides improved estimates of the state of permafrost at Bayelva. Due to the cheap computational cost, the framework is also applicable to much larger model domains. Moreover, given the robustness, owing to the global span of the satellite retrievals and the option of running SSNOWD with reanalysis data (e.g. ERA-Interim), it is possible to apply this framework to most permafrost regions on the planet.

Description: 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.

Description: Published

Description: 76-91

Description: 4.6. Oceanografia operativa per la valutazione dei rischi in aree marine

Description: N/A or not JCR

Description: open

Description: 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.

Description: Submitted

Description: Nice, France

Description: 3.11. Oceanografia Operativa

Description: open

Description: GEROS-ISS stands for GNSS REflectometry, radio occultation, and scatterometry onboard the International Space Station (ISS). It is a scientific experiment, successfully proposed to the European Space Agency in 2011. The experiment as the name indicates will be conducted on the ISS. The main focus of GEROS-ISS is the dedicated use of signals from the currently available Global Navigation Satellite Systems (GNSS) in L-band for remote sensing of the Earth with a focus to study climate change. Prime mission objectives are the determination of the altimetric sea surface height of the oceans and of the ocean surface mean square slope, which is related to sea roughness and wind speed. These geophysical parameters are derived using reflected GNSS signals (GNSS reflectometry, GNSS-R). Secondary mission goals include atmosphere/ionosphere sounding using refracted GNSS signals (radio occultation, GNSS-RO) and remote sensing of land surfaces using GNSS-R. The GEROS-ISS mission objectives and its design, the current status, and ongoing activities are reviewed and selected scientific and technical results of the GEROS-ISS preparation phase are described.