Uncertainties: Model versus forcing • 2 models: HOPE and NEMO • Similar horizontal resolution (~1 deg + eq refinement) • Different grids, different vertical discretization, different numerics, different physics • 2 sets of forcing fluxes: ERA-40/OPS and ERA-Interim • Integrations: • 1989-2006 • Daily fluxes • Strong relaxation to SST

Heat flux corrections: • In The Eastern Pacific the solution depends mainly on the ocean model • In the Equatorial Indian the solution depends mainly on the forcing fluxes

Total sea level Differences due to models Differences due to forcing fluxes

Surface Salinity Differences due to models Differences due to forcing fluxes

Solar Heat flux: Era Interim – Era 40

Flux correction term (~ SST error) ERA-40 ERA-INTERIM

Wind Stress

Meridional wind stress time series ERA-40/OPSERA-INTERIM

T300

Correlation with Altimeter date ERA-40 ERA-INTERIM

IFS/HOPE (3 members) IFS/HOPE: impact of ocean observations Global mean near-surface air temperature anomaly (2-year running mean applied) from the ECMWF re-forecasts. ERA40/OPS is used as a reference. The mean systematic error has been removed over the period 1960-2005. IFS/HOPE NoObs

Estimation of the Atlantic MOC Assimilation No-DataBryden etal 2005Cunningham etal 2007 From Balmaseda etal 2007

IFS/HOPE: impact of ocean observations Zonally integrated across the Atlantic meridional water velocity (103 m2/s) from the ECMWF ocean re-analysis (left)and the mean of the ten ECMWF re-forecasts Assim (centre) and NoObs (right). 27°N Profiles below 150m 36°N

Perceived Paradigm for initialization of coupled forecasts Real world Model attractor Medium range Being close to the real world is perceived as advantageous. Model retains information for these time scales. Model attractor and real world are close? Decadal or longer Need to initialize the model attractor on the relevant time and spatial scales. Model attractor different from real world. Seasonal? Somewhere in the middle? At first sight, this paradigm would not allow a seamless prediction system. • Experiments: • Uncoupled SST + Wind Stress + Ocean Observations (ALL) • Uncoupled SST + Wind Stress (NO-OCOBS) • Coupled SST (SST-ONLY) (Keenlyside et al 2008, Luo et al 2005)

Impact of “real world” information on skill: NINO3.4 RMS ERROR ALLNO-OCOBS SST-ONLY Adding information about the real world improves ENSO forecasts From Balmaseda and Anderson 2009

Reduction (%) in SST forecast errorRange 1-3 months In Central/Western Pacific, up to 50% of forecast skill is due to atmos+ocean observations. Sinergy: > Additive contribution Ocean~20% Atmos ~25% OC+ATM~55% NINO-W EQATL STIO WTIO EQ3 Impact of “real world” information on skill:

Western Pacific • Relation between drift and Amplitude of Interannual variability. • Upwelling area penetrating too far west leads to stronger IV than desired. Impact of Initialization Eastern Pacific ALL NO-OCOBS SST-ONLY DRIFT • Drift and Variability depend on Initialization !! • More information corrects for model error, and the information is retained during the fc. • Need “more balanced” initialization methods to prevent initialization shock hitting non linearities VARIABILITY • Relation between drift and Amplitude of Interannual variability. • Possible non linearity: is the warm drift interacting with the amplitude of ENSO?

Pacific Panel Input: • General proposal • 0. Scientific Questions • 1. Process oriented metrics (with/without observations) • 2. Generic (blanket) metrics (with/without observations) • METRICS and/or DIAGNOSTICS? • Ongoing work on ENSO metrics to evaluate climate models (Pacific Panel, Eric Guilyardi).

CORE-II draft proposal from Pacific Panel (summary I) • Relevant scientific questions • Which processes control the SST off the South American coast, and why models are not able to represent it correctly? Link to VOCALS • Which are the determining factors for ocean models to represent the depth and slope in equatorial thermocline? • What controls the intensity and extension of the cold tongue? • What is the heat budget of the warm pool? • What determines the Equatorial heat content? What are the ocean heat and fresh water transports at the equator? • Which is the origin of the water masses in the Indonesian Troughflow (ITF), which will determine the ITF heat and fresh water transports.? • Which is the heat transport done by Tropical Instability Waves? • SPICE science questions? • Equatorial currents. Tsuchiya jets. • Barrier Layer.

CORE-II draft proposal from Pacific Panel (summary II) • 1 Relevant metrics for process studies • 1.1Observed • Depth of the 20D isotherm along the Equator: Mean, SVD, RMS/RMSE, and ACC (TAO/TRITON observations). • Structure of the Tropical Instability Waves (TWI): Power spectra as a function of latitude (Altimeter data and SST) • Indonesian Throughflow (IT): Volume transport, Water mass properties of the waters in that region. (Verifying observations?) • Barrier Layer (Maes et al,…) • South American Upwelling: VOCALS area SST, upwelling, meridional velocity…Verifying observations: Stratus BUOY, Stratus cruise. • SPICE Region: U,V,T,S. There will be verifying observations

CORE-II draft proposal from Pacific Panel (summary II) • 1 Relevant metrics for process studies • 1.2NonObserved • Heat and volume transports by TWIs • Heat budget in the warm pool region • Indonesian Throughflow: heat and fresh water mass transport. • Origin of waters in the IT? • Trends in the Equatorial Circulation? • …..

CORE-II draft proposal from Pacific Panel (summary III) • 2. Generic metrics • 2.1 Observed • Temperature and Salinity profiles in prescribed areas (to include attachment with Pacific_areas), compared with observations. Mean, SDV, mean difference/error and RMS/RMSE. • T/S Observations are from WOA05 or from the Hadley Centre EN3. • T/S and Currents profiles at TAO/TRITON mooring location. Mean, SDV, mean difference/error, RMS/RMSE and ACCTAO/TRITON observations. • 2.2 Non observed: (comparable with reanalysis and obs-only analysis) • Zonal sections along the Equator of T,S,U,V,W: Mean, SDV, mean difference, RMS. • Meridional sections or T,S,U,V,W: Mean, SDV, mean difference, RMS. Longitudes: 137E, 165E, 180,140W, 110W, 95W • Others...