ENSO and tropical Pacific metrics for coupled GCMs

1
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

2
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.

3
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,
  ...)

4
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

5
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
• East130W- 90W, 5N - 5S
• West150E-170W, 5N - 5S
• SlopeWest-East
• Goal to have an idea of existing uncertainty,
  and whether the ocean reanalysis from GSOP can be
  used to validate coupled models.

6
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?
• or
• Individual reanalyses to compute indices and
  Pacific Panel members to compile/summarize.

7

• Views and suggestions to
• Eric.Guilyardi_at_locean-ipsl.upmc.fr
• Magdalena.Balmaseda_at_ecmwf.int
• axel_at_hawaii.edu