WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Based in part on …
Some Scale Considerations for Some Scale Considerations for Predicting/Projecting Extreme Predicting/Projecting Extreme
PrecipitationPrecipitation
William J. Gutowski, Jr.William J. Gutowski, Jr.Iowa State University Iowa State University
U.S.A.U.S.A.
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Methodologies for Estimating ExtremesMethodologies for Estimating Extremes
Simulated time & space scalesSimulated time & space scales
Process behavior under climate changeProcess behavior under climate change
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Cold Half of Year
95%
Precipitation:Precipitation:Frequency vs. IntensityFrequency vs. Intensity
~~ Averaging Time Averaging Time
(Gutowski et al. 2003)(Gutowski et al. 2003)
6-hourly
daily
10-day
Simulation:Simulation:
Continental U.S.Continental U.S.
1979-19881979-1988
50-km grid50-km grid
NCEP Reanalysis 1NCEP Reanalysis 1
Analysis:Analysis:
Central U.S.Central U.S.
8 years of 8 years of
October - October - March March
April - May April - May
95%
Warm Half of Year
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Precipitation:Precipitation:Frequency vs. IntensityFrequency vs. Intensity
~~ Spatial Scale Spatial Scale
Simulation:Simulation:
Continental U.S.Continental U.S.
1979-19881979-1988
50-km grid50-km grid
Analysis:Analysis:
Central U.S.Central U.S.
8 years of October - 8 years of October - March March
(Gutowski et al. 2003)(Gutowski et al. 2003)
[km]
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
NARCCAP SimulationsNARCCAP Simulations
• DomainDomain
- Most of North America- Most of North America
• ResolutionResolution
~ 50 km~ 50 km
• Simulation PeriodSimulation Period
- 1978-2004- 1978-2004
• Boundary ConditionsBoundary Conditions
- NCEP/DOE reanalysis- NCEP/DOE reanalysis
MM5MM5Iowa Iowa
State/State/PNNLPNNL
RegCM3RegCM3UC Santa CruzUC Santa Cruz
ICTPICTP
CRCMCRCMQuebec,Quebec,OuranosOuranos
HADRM3HADRM3Hadley CentreHadley Centre
RSMRSMScrippsScripps
WRFWRFNCAR/NCAR/PNNLPNNL
PLUS:GFDL Atmosphere GCM- 0.5˚ resolution- specified SST/ice for same period
NCAR CCSM Atmosphere-Ocean GCM- 1.4˚ (T85) resolution- analysis for same period
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Comparison with Comparison with observationsobservations
• Observation-based FieldsObservation-based Fields Precip: University of Washington VIC retrospective analysisPrecip: University of Washington VIC retrospective analysis
Other fields: North American Regional ReanalysisOther fields: North American Regional Reanalysis
• Comparison period: 1982 -1999Comparison period: 1982 -1999 1979-1981 omitted - spinup1979-1981 omitted - spinup UW data end in mid-2000UW data end in mid-2000
• AnalysisAnalysis ““Precipitation event” = Daily precip ≥ 2.5 mm at a grid pointPrecipitation event” = Daily precip ≥ 2.5 mm at a grid point Focus on precip intensity ≥ 99.5% Focus on precip intensity ≥ 99.5%
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Regions AnalyzedRegions Analyzed
Boreal forest
Pacific coast
California coast
Great LakesMaritimes
Upper Mississippi
River
Deep South
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Precipitation Frequency vs. IntensityPrecipitation Frequency vs. Intensity
99.5%
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Days with Simultaneous Extremes on Days with Simultaneous Extremes on “N” Grid Points“N” Grid Points
“widespread extremes”
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Composite Structure of Extreme Events - DJFComposite Structure of Extreme Events - DJF
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Composite Structure of Extreme Events - DJFComposite Structure of Extreme Events - DJF
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Composite Structure of Extreme Events - DJFComposite Structure of Extreme Events - DJF
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Present & Future Climate – Earlier ResultsPresent & Future Climate – Earlier Results
Control-driven
NCEP-driven Scenario-driven
500 hPa Heights
(Gutowski et al. 2008)(Gutowski et al. 2008)
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Precipitation Changes?Precipitation Changes?
Future – CurrentFuture – Current
0.05% Threshold0.05% Threshold + 17% + 17%
Extreme Precip. Extreme Precip. + 26%+ 26%
Extreme precipitation as max humidity
Max atmospheric humidity ~ 7% per degree
Projected temperature increase: ~ 2.5˚C
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Africa: Water Balance ChangesAfrica: Water Balance Changes(IPCC AR4 WG1)(IPCC AR4 WG1)
2080-2099 Minus 1980-19992080-2099 Minus 1980-1999 # models with # models with > 0 > 0
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Africa: Africa: Precipitation via Statistical Downscaling Precipitation via Statistical Downscaling
2070-20992070-2099
VsVs
30-yr pres30-yr pres
2080-20992080-2099
vs.vs.
30-yr pres30-yr pres
Range: Range:
[-80,+80] [-80,+80] mm/monthmm/month
(Hewitson & (Hewitson & Crane, 2006)Crane, 2006)
WCRP Metrics/Methodologies for ExtremesWCRP Metrics/Methodologies for Extremes September 2010September 2010
Higher resolution is necessary, but not sufficient, for Higher resolution is necessary, but not sufficient, for simulating short-term (e.g., daily) precipitation simulating short-term (e.g., daily) precipitation extremes.extremes.
Coarser models (and nudged regional models) tend to Coarser models (and nudged regional models) tend to have daily extremes covering a wider area than have daily extremes covering a wider area than observed extremes. observed extremes.
Focusing on environments conducive to extremes Focusing on environments conducive to extremes yields relevant climatic behavior, even in relatively yields relevant climatic behavior, even in relatively coarse models.coarse models. This conclusion rests on the assumption that important This conclusion rests on the assumption that important
small-scale features are not missing (e.g., low-level small-scale features are not missing (e.g., low-level jets).jets).