Developments within FOAM Adrian Hines, Dave Storkey, Rosa Barciela, John Stark, Matt Martin IGST, 16 Nov 2005

Open ocean forecasting: FOAM – Forecasting Ocean Assimilation Model Present systems & recent developments

Overview of the FOAM system Operational real-time deep-ocean forecasting system Daily analyses and forecasts out to 5 days Hindcast capability (back to 1997) Relocatable high resolution nested model capability FOAM = Forecasting Ocean Assimilation Model Real-time data Obs QC & processing Analysis Forecast to T+120 NWP 6 hourly fluxes Automatic verification T+24 forecast used in QC Product dissemination Operational system Hindcast system

Model & Operational system Ocean model –Z-level, primitive equation model –Same code as used in Hadley Centre climate models –Rigid lid –Kraus-Turner + K-profile vertical mixing –Simple advective sea-ice model –Flow Relaxation Scheme at open boundaries for nested models Operational system –Three suites of nested models: QO00: Global, North Atlantic and Mediterranean, starts at 05:00Z QN00: Indian Ocean, starts at 00:30Z QV00: Antarctic, starts at 01:45Z –Run daily on 7 NEC SX6 processors –Responsibility of operational teams; 7-day operator support –Boundary data provided to operational Shelf Seas model –Automated verification system running at T+7 days

Operational configurations 12km (1/9º) Mediterranean 36km (1/3º) North Atlantic and Arctic 12km (1/9º) North Atlantic 1º Global 36km (1/3º) Indian Ocean 12km (1/9º) Arabian Sea 27km (1/4º) Antarctic All configurations run daily in the operational suite Output available on HORACE

Data assimilation Data assimilation is key to initialising the models for effective forecasting All FOAM configurations assimilate a range of data: –Temperature and salinity profiles including Argo floats –Satellite altimeter Sea Surface Height –In situ and satellite Sea Surface Temperature New generation of satellite SST products being tested –Sea-ice concentration Argo float distribution at end of March Improved satellite SST data Current SatSST data: c obs dailyNew data: Atlantic > 2.5 million obs daily

Partial Cell Bathymetries Improved topographic steering of currents Model bathymetryModel streamfunction Full cells Partial cells

Dependence of forecast bias on advection scheme Annual mean of analysis temperature increments along 65ºW 3D QUICK4 th order + biharmonic GM

Assessments of Mixed Layer Careful assessment of mixed layer schemes using Argo and OWS Papa data More reliable diagnostic of mixed layer developed Global mean mixed layer depth error Old MLDNew MLD

Ecosystem, air-sea CO 2 fluxes and water clarity Hadley Centre Ocean Carbon Cycle model (HadOCC) has been coupled with the FOAM system FOAM-HadOCC running at 1º, 1/3º and 1/9º resolution Assessment of initial year-long integrations underway Diagnostics of pCO 2 and water clarity Ocean colour data assimilation scheme (developed by NOCS) implemented and testing commenced Chlorophyll for mid-March º FOAM- HadOCC SeaWIFS data

Sea-ice data assimilation A system for assimilating sea- ice concentration data into FOAM has been developed with funding from ESA –Assimilation improves representation of the ice, especially the ice edge A scheme for the assimilation of ice velocity has also been developed which adapts the stresses on the ice to match observations

Assimilation of Altimeter Data Surface pressure difference Identical twin experiments used to explore poor performance Bottom pressure errors are up to 30% of surface errors Old MLDNew MLD Bottom pressure difference