1. TOPAZ monitoring and forecasting system Laurent BERTINO, Knut Arild LISÆTER, Nina WINTHER, François COUNILLON, Hanne SAGEN, Cecilie HANSEN, Intissar KEGHOUCHE and Geir EVENSEN Mohn-Sverdrup Center for Global Ocean Studies and Operational Oceanography, c/o Nansen Environmental and Remote Sensing Center Contact: Laurent.Bertino@nersc.no, NERSC, Thormølensgt. 47, N-5006 Bergen, NorwayLaurent.Bertino@nersc.no Seasonal circulation Coastal dynamics Atmospheric Data Atmospheric Data Satellite Data SLA, SST, ice c. In Situ Data Improve the understanding of the ocean circulation and variability in the Ocean and its predictability EnKF Data assimilation System Local assimilation (EnOI) Ocean forecasting capabilities Ocean forecasting capabilities Inter-decadal variability Inter-decadal variability Atlantic and Arctic Basin model Coastal model Regional model References Assimilation of ice concentration in a coupled ice-ocean model, using the Ensemble Kalman Filter Knut Arild Lisæter, Julia Rosanova, Geir Evensen, Ocean Dynamics, 53, 368-388, 2003. The Ensemble Kalman Filter: Theoretical Formulation and Practical Implementation Geir Evensen, Ocean Dynamics, 53, 343-367, 2003. A demonstration of ensemble based assimilation methods with a layered OGCM from the perspective of operational ocean forecasting systems, K. Brusdal, J.M. Brankart, G. Halberstadt, G. Evensen, P. Brasseur, P. J. van Leeuwen, E. Dombrowsky and J. Verron, JMS, 40-41, 253-289, 2003 Geopolitics TOPAZ is the Norwegian contribution to GODAE. TOPAZ is the Arctic component in MERSEA NERSC met.no and the IMR collaborate in the MONCOZE project. HYCOM is selected as the future operational forecasting capability of the U.S. Navy (NRL) NERSC collaborates with NRL through NOPP. TOPAZ is duplicated at the Nansen-Zhu Center in Beijing, for forecasting the Pacific Ocean and South China Sea. Description The TOPAZ system uses the Hybrid Coordinate Ocean Model (HYCOM) developed by RSMAS, University of Miami. In TOPAZ HYCOM has been coupled to: A sea-ice model, based on the rheology by Hunke and Dukowicz (1998) and a multi-category sea-ice model. Three ecosystem models, including the Fasham model and the Carbon-Nitrogen Regulated Ecosystem Model (REcoM) from AWI. Observations are used for assimilation and verification of forecast: Sea Level Anomalies from altimetry (SSALTO-DUACS, CLS) Sea Surface Temperature from AVHRR (1/4 th degree maps, CLS) Sea-ice concentrations from SSM/I (NSIDC) In-situ data from ARGO floats, XBT, etc. (CORIOLIS, Ifremer) Ocean Colour from MODIS (CLS) The EnKF assimilates these different data types in the coupled model using an ensemble of model states to represent the uncertainty. The TOPAZ system was mainly developed by two successive EC projects, DIADEM (1999-2000, MAST-3) and TOPAZ (2001-2003, FP5), its real-time operation is continuous since January 2003 thanks to the MERSEA IP and a private endowment by Trond Mohn c/o Frank Mohn AS, Bergen. Objective: TOPAZ is a real-time data assimilative 3D ocean forecasting system aimed at providing quality boundary conditions to high-resolution (eddy resolving) local forecasting systems for ocean currents, sea-ice and ecosystems. Verification of model nowcast sea surface heights (lines) with posterior satellite observations (SST, CLS). Eddy Vortex, 28 th February 2005. Gulf of Mexico: A nested data assimilative HYCOM model forecasts the eddies and the evolution of the Loop Current. An added- value forecast service is provided by Ocean Numerics Ltd.* to the offshore oil industry. The local data assimilation method is an ensemble OI (EnOI) for sea level anomalies. * Ocean Numerics is a joint venture of the Nansen Centre, Fugro GEOS and CLS. See forecast bulletins and validation results on http://topaz.nersc.no http://topaz.nersc.no Barents Sea: A nested HYCOM model (4km resolution) simulates the currents and sea-ice. The model is intended to support iceberg forecasting. North Sea: A nested HYCOM model (4km resolution) simulates the currents. The model is used in the MONCOZE NFR project http://moncoze.met.no intended to support ecosystem forecasting.http://moncoze.met.no Nordic Seas Perspective: The Mohn-Sverdrup center will develop an eddy resolving model of the Nordic Seas nested into TOPAZ, encompassing the above nested models. The Ensemble Kalman Filter (EnKF): Based on Monte-Carlo model simulations, the EnKF handles multivariate statistics for all non- linear systems. Explicit model errors relate the assimilation update to the uncertain model parameters. Conservation of physical properties is ensured during the ensemble update: A a = A f + K (d-HA f ) A a = A f.X 5 X 5 being typically a 100x100 matrix, the linear relationships (i.e. geostrophy) are conserved, see Evensen (2003). Evolution of ice extent over a season: Gray zone: ensemble members Bold line: ensemble mean Dashed: free-run Assimilation of ice concentrations: With the EnKF, the multivariate assimilation of ice parameters can correct the 3D ocean parameters. Impact of a single ice concentration update, summer situation, on surface temperature (top) and salinity (bottom). The salinity update changes sign depending on seasons and on active ice processes. Efficiency of ice concentration assimilation