bmrc coupled modelling: oscar alves, guomin wang, neville smith, aihong zhong, faina tseitkin,...
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BMRC coupled modelling:
Oscar Alves, Guomin Wang, Neville Smith, Aihong Zhong, Faina Tseitkin, Andrew Marshall
BMRC Model Development (NWP, Lilia Deschamps)
BMRC Climate Dynamics (Rob Colman)
CSIRO Marine Research (OGCM)
Andreas Schiller, Stuart Godfrey, Gary Meyers, Peter McIntosh, Russ Fieddler
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Biases in:
POAMA (operational coupled seasonal forecast model) 9 month forecasts
Climate Version: 100 yr run discard first 20 yrs, no flux correction
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GCM ComponentsAtmospheric model BAM3 configuration
Resolution: T47L17
Radiation: Lacis and Hansen (1974), Schwarzkopf and Fels (1991)
Convection: Tiedtke (1989): moisture convergence and CAPE closures
Land surface processes: Manabe and Holloway (1975).
Prognostic Cloud formulation: Rotstayn (1997)
Surface Fluxes: Louis (1983), McAvaney and Hess (1996)
•Resolution: meridional 0.5° within 8° of the equator, Zonal 2°; 12 levels in the top 185 metres.
•Chen mixing scheme
•penetrtative short wave radiation
•tidal mixing parameterisation in the Indonesian region
•careful representation of islands and straits in the Indonesian region
Ocean model ACOM2 configuration
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Operational Forecast Set Up• Ocean initial conditions Daily Optimum Interpolation
• Atmos. initial conditions From BoM operational NWP model
• Ensemble
– 9 month forecast everyday (within 1 day of real time)
• Anomalies from Model Climatology
– Hindcast 1983-2002
– One per month, AMIP atmospheric initial condition
– Assimilated oceanic initial condition
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SST Anomaly Correlation Skill with Lead Time
Green - model
Red - anomaly persistence
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Decay of 2002 El Nino
Forecasts available at BOM Dec 2002 SCO
POAMA
NASA
NCEP
ECMWF
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SST drift:
Problem with surface flux and clouds in stand-alone AGCM
Little impact on east Pacific drift from big changesto StratCu: suggests resolution problem near Andes
Convection:
Changes to convection parameterization improve intraseasonal variability and ITCZs in uncoupled run
Impacts coupled behavior (perhaps more realstic)
Improvements to ITCZ don’t carry over to coupled run
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SST
Drift
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Bias 100 yr climate run
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Surface short wave from AMIP run of AGCM
SRB“observed”Surf SW
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Drift at 6 month lead
AGCMNet Flux
Whatoceanwants
Diff
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Sub-surface drift suggests problem equatorial winds
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Enhanced subStrat Cu mixing
Erroneous mixing above Strat Cu
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Tropical intraseasonal variability
Moisture convergence closureNCEP re-analysis
30 days
60 days
CAPE Closure
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Mean Prec CAPE
Mean Precip Moist Convergence
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Annual mean prec coupled climate run
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Zonal wind anomaly along equator
Obs Moisture closure CAPE Closure
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SST anomaly along equatorForecast starting 1st June 1997
Obs Old: Moisture closure New: CAPE Closure
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Latent Heat
Flux
NCEP
AGCM