global climate modeling - clarkson university · climate modeling •current state of climate...
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Climatemodeling• Currentstateofclimateknowledge–Whatdoesthehistoricaldata(temperature,CO2,etc)tellus
–Whataretrendsinthecurrentobservationaldata–Whatdoweknowaboutthegreenhouseeffect
Climatemodelschematic
Source:IPCC,2007
Inputtomodels:EmissionscenariosofcarbonSO2,particles,etc
ModelscalculatetheatmosphericconcentrationofGHGs,aerosol,etc
Modelsdeterminetheimpactofthespeciesinteractingwithshortwaveandlong-waveradiation
Theatm.parameterssuchastemp,precip,etcarethendeterminedconsideringglobalcirculationpatterns,etc
IPCC,2007
Thelackofadequateknowledgeonaerosol-cloudinteractionsisacriticaluncertaintyinglobalclimatemodeling
Climatemodels• Fourcomponents:– Atmosphere,landsurface,ocean,andseaice.
• AtmosphericandOceaniccomponents–Globalcirculationmodels(GCM)– Simulatelargescalecirculationoftheatmosphereandtheoceans.
– Importantvariables• Temperature,pressure,humidity,winds,andwaterandicecondensateinclouds
Computationaldetails• TypicalAtmosphericglobalcirculationmodels(AGCMs):
– Spatialresolutionof~100kminthehorizontal– 30levelsintheverticalatmospherebelowthealtitudeof15-20
km– Timestepof10-20minutes– Withinthegrids,parameterizationsareusedtosimulate
processesthataretoocomplextocaptureintheclimatemodels.• E.g.,cloudformation,turbulence
• Oceanicglobalcirculationmodels(OGCMs)arecoupledtotheatmosphereandicemodelsthroughtheexchangeofheat,salinity,andmomentumattheboundaryamongcomponents.– Resolutionof1degreelatitudeandlongitude;30layersinthe
oceans
Climatemodels• Doublingtheresolutionwillrequire~10timesmorecomputingpower.
• Foroneyearofsimulations,needtoprocessdataover2.5milliongridcellsmorethan27,000times.
Climatemodels:Limitations• Lowresolutionlimitstheabilitytopredictfeaturessuchastornadoes,etc
• Can’tpredictEastAsianorIndianmonsoonswell
• Regionalscaleclimaticfeaturesaredifficulttopredictaccurately
Accuracyofclimatemodelpredictions
(b)Predicted
IPCC,2007
(a)Observed
(1980-1999)
Averageprecipitation Temperatureanomaly