1. WCRP Metrics/Methodologies for Extremes September 2010 Based in part on … Some Scale Considerations for Predicting/Projecting Extreme Precipitation William J. Gutowski, Jr. Iowa State University U.S.A.

2. WCRP Metrics/Methodologies for Extremes September 2010 Methodologies for Estimating Extremes  Simulated time & space scales  Process behavior under climate change

3. WCRP Metrics/Methodologies for Extremes September 2010 Cold Half of Year 95% Precipitation: Frequency vs. Intensity ~ Averaging Time (Gutowski et al. 2003) 6-hourly daily 10-day Simulation: Continental U.S. 1979-1988 50-km grid NCEP Reanalysis 1 Analysis: Central U.S. 8 years of October - March April - May 95% Warm Half of Year

4. WCRP Metrics/Methodologies for Extremes September 2010 Precipitation: Frequency vs. Intensity ~ Spatial Scale Simulation: Continental U.S. 1979-1988 50-km grid Analysis: Central U.S. 8 years of October - March (Gutowski et al. 2003) [km]

5. WCRP Metrics/Methodologies for Extremes September 2010 NARCCAP Simulations Domain Domain - Most of North America Resolution Resolution ~ 50 km Simulation Period Simulation Period - 1978-2004 Boundary Conditions Boundary Conditions - NCEP/DOE reanalysis MM5 Iowa State/ PNNL RegCM3 UC Santa Cruz ICTP CRCMQuebec,Ouranos HADRM3 Hadley Centre RSMScrippsWRFNCAR/PNNL 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

6. WCRP Metrics/Methodologies for Extremes September 2010 Comparison with observations Observation-based Fields Observation-based Fields  Precip: University of Washington VIC retrospective analysis  Other fields: North American Regional Reanalysis Comparison period: 1982 -1999 Comparison period: 1982 -1999  1979-1981 omitted - spinup  UW data end in mid-2000 Analysis Analysis  “Precipitation event” = Daily precip ≥ 2.5 mm at a grid point  Focus on precip intensity ≥ 99.5%

7. WCRP Metrics/Methodologies for Extremes September 2010 Regions Analyzed Boreal forest Pacific coast California coast Great Lakes Maritimes Upper Mississippi River Deep South

8. WCRP Metrics/Methodologies for Extremes September 2010 Precipitation Frequency vs. Intensity 99.5%

9. WCRP Metrics/Methodologies for Extremes September 2010 Days with Simultaneous Extremes on “N” Grid Points “widespread extremes”

10. WCRP Metrics/Methodologies for Extremes September 2010 Composite Structure of Extreme Events - DJF

11. WCRP Metrics/Methodologies for Extremes September 2010 Composite Structure of Extreme Events - DJF

12. WCRP Metrics/Methodologies for Extremes September 2010 Composite Structure of Extreme Events - DJF

13. WCRP Metrics/Methodologies for Extremes September 2010 Present & Future Climate – Earlier Results Control-driven NCEP-driven Scenario-driven 500 hPa Heights (Gutowski et al. 2008)

14. WCRP Metrics/Methodologies for Extremes September 2010 Precipitation Changes? Future – Current 0.05% Threshold+ 17% Extreme Precip. + 26% Extreme precipitation  as max humidity  Max atmospheric humidity  ~ 7% per degree Projected temperature increase: ~ 2.5˚C

15. WCRP Metrics/Methodologies for Extremes September 2010 Africa: Water Balance Changes (IPCC AR4 WG1) 2080-2099 Minus 1980-1999 # models with  > 0

16. WCRP Metrics/Methodologies for Extremes September 2010 Africa:  Precipitation via Statistical Downscaling 2070-2099Vs 30-yr pres 2080-2099vs. Range: [-80,+80] mm/month (Hewitson & Crane, 2006)

17. WCRP Metrics/Methodologies for Extremes September 2010  Higher resolution is necessary, but not sufficient, for simulating short-term (e.g., daily) precipitation extremes.  Coarser models (and nudged regional models) tend to have daily extremes covering a wider area than observed extremes.  Focusing on environments conducive to extremes yields relevant climatic behavior, even in relatively coarse models.  This conclusion rests on the assumption that important small-scale features are not missing (e.g., low-level jets).

18. WCRP Metrics/Methodologies for Extremes September 2010 Thank You!