GOVST III, Paris Nov 2011 ECMWF

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

GOVST III, Paris Nov 2011 ECMWF

Delayed Ocean Re-Analysis ~ORAS4 (NEMOVAR)

Real Time Ocean Analysis

ECMWF:

Forecasting Systems

ECMWF:

Forecasting Systems

Medium-Range (10-day)Partial coupling

Medium-Range (10-day)Partial coupling

Seasonal ForecastsFully coupled

Seasonal ForecastsFully coupled

Extended + Monthly Fully coupled

Extended + Monthly Fully coupled

Ocean model

Atmospheric model

Wave model

Atmospheric model

Ocean model

Wave model

Oce

an Init

ial

Condit

ions

GOVST III, Paris Nov 2011 ECMWF

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)

Woolnough et al, MWR 2007

Anomaly Correlation

Persisted SST anomalies

OGCM (10 m vertical res)

Mixed layer (1 m vertical res)

GOVST III, Paris Nov 2011 ECMWF

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

GOVST III, Paris Nov 2011 ECMWF

Bulk formula modifications (Hersbach, Janssen 2008)

OLD-NEW: Taux OLD-NEW: Mixed Layer Depth OLD-NEW: SST

• 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

GOVST III, Paris Nov 2011 ECMWF

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)