ENSO and tropical Pacific metrics for coupled GCMs Eric Guilyardi on behalf of the ad hoc WG of the CLIVAR Pacific Panel Goals: Document the performance of ENSO and tropical simulation in CMIP coupled models. Help better understanding of processes in models and identify new mechanisms Establish guidance for multi-model ensembles means (rejection of inadequate models, weighting, etc.) Audience: Model developers Non ENSO specialists, producers/users of climate change projections

ENSO metrics guidelines Definition. A metric is defined as a single scalar which measures the model performance, i.e. some “distance” of the model result to the reference observation/reanalysis. Any other analysis is referred to as a diagnostic. Priority: identify the “magic” 5 to 7 ENSO metrics that are essential among the many identified. Also key to document the background systematic errors in the tropical Pacific.

ENSO metrics categories Base ENSO metrics Ocean subsurface (e.g. warm water volume, thermocline sharpnes, etc...) Surface (e.g. Niño 3,4,... SSTA stddev indices, seasonal phase lock, ENSO period, Trans-Niño index,...) Atmosphere (e.g. SOI, ISO variability, ...) Background systematic errors (e.g. cold tongue, trade winds strength, eastern edge of the warm pool,...) ENSO Feedbacks (Bjerknes, heat flux, ...) ENSO teleconnections (with Asian monsoon, PNA, ...)

Collaboration with GSOP ? Help identify ocean references: Re-analysis (ORA-S3, SODA, ECCO,NCEP, Ishii,...) Ocean heat content or other subsurface proxy Velocity (TAO, OSCAR, ARGO,...) Temperature and salinity (TAO, XBTs, ARGO,...) Help test some ideas of ocean-related metrics

Collaboration with GSOP ? For example: Time series of Upper 300m of Equatorial heat content: to identify the trends Thermocline depth and slope: time series in East and West Pacific. Suggestions: East:130W- 90W, 5N - 5S West:150E-170W, 5N - 5S Slope=West-East Goal: to have an idea of existing uncertainty, and whether the ocean reanalysis from GSOP can be used to validate coupled models.

Collaboration with GSOP ? QUESTION: which is the more practical approach? GSOP to compute/compile and summarize indices recommended by the Pacific Panel or Pacific Panel to access GSOP reanalyses via OPenDap servers? Individual reanalyses to compute indices and Pacific Panel members to compile/summarize.

Views and suggestions to: Eric.Guilyardi@locean-ipsl.upmc.fr Magdalena.Balmaseda@ecmwf.int axel@hawaii.edu