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ECMWF Activities on Coupled Forecasting Systems

ECMWF Activities on Coupled Forecasting Systems. Status Ongoing research Needs for MJO Bulk formula in ocean models Plans. New Marine Aspects Section Peter Janssen (head) Ocean/Sea Ice Waves Serving all time scales: analysis, medium range, monthly and seasonal. Atmospheric model.

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ECMWF Activities on Coupled Forecasting Systems

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  1. ECMWF Activities on Coupled Forecasting Systems • Status • Ongoing research • Needs for MJO • Bulk formula in ocean models • Plans • New Marine Aspects Section • Peter Janssen (head) • Ocean/Sea Ice • Waves • Serving all time scales: analysis, medium range, monthly and seasonal

  2. Atmospheric model Atmospheric model Wave model Wave model Ocean model Ocean model Real Time Ocean Analysis Delayed Ocean Re-Analysis ~ORAS4 (NEMOVAR) ECMWF: Forecasting Systems Medium-Range (10-day) Partial coupling Seasonal Forecasts Fully coupled Extended + Monthly Fully coupled Ocean Initial Conditions

  3. Monthly Forecasts needs • Madden Julian Oscillation (MJO) is corner stone for monthly forecasting (as ENSO is for seasonal) • It influences NAO regimes (Cassau et al 2008) and predictability over Europe (Vitart) • MJO forecasts needs interactive ocean, good representation of ocean mixing (high vertical resolution) Anomaly Correlation Persisted SST anomalies OGCM (10 m vertical res) Mixed layer (1 m vertical res) Woolnough et al, MWR 2007

  4. MJO revisited: PC1 and PC2 • Models have improved: Even Persisted SST crosses the 0.6 value after day 20. • Performance of persisted SST anomaly, current practice, is easy to beat by introducing coupling with the ocean. • Not much differences between 1D KPP and 3D NEMO (10m level thickness) • Now there is a diurnal layer scheme in the atmosphere • NEMO mixing better than HOPE? • The Observed SST (even weekly product) still better than coupling • What is the performance with OSTIA? • Can we expect to beat observed SST? Courtesy of Eric de Boisseson

  5. Bulk formula modifications (Hersbach, Janssen 2008) • Ultimately: to use the same bulk formula as in the atmosphere model (IFS) • First Sensitivity: modify the empirical function for the drag coefficient as a function of wind speed to simulate the results from the IFS. It produces stronger drags for high winds. • Impact on windstress ~ 10%. It impacts mixed layer depth. It reduces SST errors OLD-NEW: Taux OLD-NEW: Mixed Layer Depth OLD-NEW: SST

  6. Plans • Implement Sea Ice model • Coupled it to monthly and seasonal forecasts • Initialization of the sea-ice model • Improve the Air-Sea interaction physics • Bulk formula for estimation of fluxes (include wave effects, use IFS formula) • Impact of waves in ocean mixing • Improve Air-Sea interaction software infrastructure • Single executable • Develop software for a Coupled Ocean-Atmosphere Reanalyses System (timeline uncertain)

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