1. Progress in Downscaling Climate Change Scenarios in Idaho Brandon C. Moore

2. Outline Datasets Methodologies Downscaling at the University of Idaho Results Summary

3. Datasets GCM Observed 8 km ~220 km 8 km Problems: (1) GCM too coarse for local assessment (2) GCM biases in climatology (spatially and temporally) (3) Regional climate variability (topography, water) 4 km

4. Datasets Which datasets should we use? –Climatology –Historic trends –Extremes –Multi-model Ensemble Weighted-average

5. Methodology Delta Method –Apply simple scaling factor; easy to use –Assumes fixed step change; higher stat. moments unchanged Bias Correction Spatial Downscaling –Wood et al, 2004; Maurer, 2007 Constructed Analog –Hidalgo et al, 2008

6. Bias Correction Spatial Downscaling (BCSD) Aggregate gridded OBS to GCM resolution** (= 1K) Remove trend Generate CDF of observed and GCM data** –Q-Q mapping approach –Z-score approach (mean and variability) Add trend back in Resample/interpolate** to finer resolution Apply spatial factor to account for subgrid topography

7. Relative to Climate Scenarios 1°K 1K uncertainty in downscaling is comparable to the spread of the models around 2050. Not as significant at 2100

8. Construct Analog Aggregate observed to GCM resolution Apply a bias correction on the GCM Determine 30 “best” synoptic patterns based on pattern RMSE –Must be chosen within 45 day window of target date Determine regression coefficients at coarse resolution Apply regression coefficients to fine-scale patterns

9. Downscaling at UI Construct Analog –Downscaled daily –Tmax, Tmin, Prcp, 10m winds, RHmax, RHmin –Late 20 th century (1971-2000) –Late 21 st century (2081-2100); A1B –Spatial resolution: 8km –13 Global Circulation Models –Additional scenarios/time slices to come

10. Downscaling at UI Modified BCSD –Downscaled monthly; moving toward daily –20 th and 21 st century –Tmax, Tmin, Prcp –Spatial resolution: 4km –3 models, 2 scenarios –Additional models and scenarios to be completed

11. Change in Cool Season (Oct-May) Precipitation Percent Change Late 21st Century SRES-A1B vs. Late 20th Century 20C3M MME

12. Change in Snowfall (SWE%) Percent Change Late 21st Century SRES-A1B vs. Late 20th Century 20C3M MME

13. Projections of annual temperature trends for the state of Idaho

14. Summary Multiple downscaled climate scenarios for ensemble runs –2 methods –Multiple models –Multiple resolutions Future work –Validation –Methods publication –Prepare for AR5 Meeting in Portland next week

15. References Hidalgo, H., Dettinger, M., and Cayan, D., 2008. Downscaling with constructed analogues—Daily precipitation and temperature fields over the United States: California Energy Commision PIER Final Project Report CEC-500-2007-123, 48 p. Maurer, E. P., 2007. Uncertainty in hydrologic impacts of climate change in the Sierra Nevada, California under two emissions scenarios, Climatic Change, Vol. 82, No. 3-4, 309-325. Wood, A. W., L. R. Leung, V. Sridhar, and D. P. Lettenmaier, 2004. Hydrologic implications of dynamical and statistical approaches to downscaling climate model outputs. Climatic Change, 62, 189-216.