Open ocean forecasting: FOAM – Forecasting Ocean Assimilation Model adrian.hines@metoffice.uk

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

2. Present systems & recent developments Open ocean forecasting: FOAM – Forecasting Ocean Assimilation Model adrian.hines@metoffice.gov.uk

3. Overview of the FOAM system Operational system Hindcast system NWP 6 hourly fluxes T+24 forecast used in QC Obs QC & processing Analysis Forecast to T+120 Automatic verification Real-time data Product dissemination FOAM = Forecasting Ocean Assimilation Model • 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

4. 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

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

6. Data assimilation Argo float distribution at end of March • 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 Improved satellite SST data Current SatSST data: c. 3000 obs daily New data: Atlantic > 2.5 million obs daily

7. Partial Cell Bathymetries • Improved topographic steering of currents Model bathymetry Model streamfunction Full cells Partial cells dave.storkey@metoffice.gov.uk

8. Dependence of forecast bias on advection scheme Annual mean of analysis temperature increments along 65ºW 3D QUICK 4th order + biharmonic GM dave.storkey@metoffice.gov.uk

9. Assessments of Mixed Layer Global mean mixed layer depth error • Careful assessment of mixed layer schemes using Argo and OWS Papa data • More reliable diagnostic of mixed layer developed Old MLD New MLD david.acreman@metoffice.gov.uk

10. Ecosystem, air-sea CO2 fluxesand water clarity Chlorophyll for mid-March 2000 • 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 pCO2 and water clarity • Ocean colour data assimilation scheme (developed by NOCS) implemented and testing commenced 1º FOAM-HadOCC SeaWIFS data rosa.barciela@metoffice.gov.uk

11. 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 john.stark@metoffice.gov.uk

12. Assimilation of Altimeter Data Identical twin experiments used to explore poor performance Bottom pressure errors are up to 30% of surface errors Old MLD New MLD Surface pressure difference Bottom pressure difference matthew.martin@metoffice.gov.uk