SSST = Scenario SST anomalies
The anomalous SST fields include more than one
scenario for the SST anomalies predicted in at least one ocean basin. This
design began in June 2004, when three possible SST scenarios were defined
for the tropical Pacific SST, each representing the prediction from one of
three SST prediction tools: (1) the NCEP coupled model, (2) the Lamont-
Doherty Earth Observatory (LDEO) simple coupled model, and (3) the NCEP/
Climate Prediction Center's constructed analogue statistical model.
For each atmospheric model, an ensemble of runs is forced with each SST
scenario.
The benefit of the multiple scenario design is that uncertainty in the SST
prediction is included explicitly. Uncertainty in the future seasonal climate
now includes both uncertainty in the initial climate state and uncertainty
in the evolution of the bourndary forcing (i.e. SSTs).
The method of defining and using multiple SST scenarios may evolve over time.
Beginning June 2004, the following numbers of ensemble members are produced
by each of the several AGCMs used in the multi-model ensemble:
SSST PSST
Scen1 Scen2 Scen3
Echam4.5 8 8 8 24
NCEP 10 10 10
Scripps 4 4 4 10
NSIPP 4 4 4
COLA 10 10 10
Internal Note
In the naming of files representing the AGCM ensemble runs, for models
other than Echam4.5, 6 digits are now used instead of 5 digits. For
Echam4.5, 9 digits are still used, as has been the case. When the
first digit is 2, the PSST scenario is used. When it is 3, the former
"ASST" scenario is used. For the new multiple scenario SST forecasts
(SSST), the first digit is 4. In the case of SSST, files representing
members coming from any one of the multiple SST scenarios are
distinguishable: The first one-third of the ensemble members are forced
by the NCEP coupled model SST prediction, the second one-third of the members by the LDEO simple coupled model SST prediction, and the third
one-third by the CPC constructed analogue SST prediction.