1. High and Dry: Declining Precipitation in the Mountains of the Pacific Northwest Charles Luce US Forest Service Research. Boise, ID John Abatzoglou University of Idaho Zachary Holden US Forest Service R1, Missoula, MT

4. Fu et al., 2010 Luce and Holden, 2009 Clark, 2010 Declining PNW Streamflows Luce and Holden, 2009

5. Two Kinds of ‘Trends’ Change in Mean Change in Variability Or Extremes

6. Middle Fork Boise – Trend in Water Yield Quantiles 75 th %ile 50 th %ile 25 th %ile Luce and Holden, 2009

7. 25 th – Dry Years 75 th – Wet Years 50th Mean Luce and Holden, 2009

8. Change in 25 th %ile annual flow Luce and Holden, 2009

9. Why? EP

10. Trends in HCN2 Precipitation (% change in 25 th %ile)

11. Energy Balance of a Surface Net Incoming Radiation Heat Lost through Evaporation Temperature Change =+

12. 1.8 W/m 2 4.2 W/m 2 Insufficient Additional Energy Available to Evaporate Water

14. Precipitation Gage Watershed Max Mean Min

15. Kirshbaum and Smith, 2008 Orographic Precipitation

16. Precipitation Correlation with Regional Westerly Wind Speed HCN Station Snotel Station

17. Precipitation Correlation with Regional Westerly Wind Speed

18. Nov-Mar Westerly Winds 42.5-47.5 N, 115-130 W

19. Changed Wind Changed Wind Changed Precipitation Changed Precipitation Changed Streamflow The Story So Far …

20. Why did the wind slow?

21. U700=f(MEI,PNA,PDO), R 2 =0.37, P<0.001 Influence of Climate Modes on Wind

22. PDO

23. Lutz et al., 2012 Gedalof et al., 2004 Tree Ring Flow Reconstructions

24. Trends and Future Predictions

25. Why would warming slow the westerlies?

26. Future Changes in Pressure

27. Historical Trends in Nov-Mar 500hPa Height

28. Interannual Variations in Nov-Mar Westerlies

30. Future Wind Changes – from GCMs 20 of 24 models show a decline for the region studied!

31. Drivers of PPTN Change Dynamic – Spreading Hadley Cell – Northward shift in jetstream – Changing winds over mountains Thermodynamic – Clausius-Clapeyron Relationship – Higher Lifting Condensation Level – Cloud microphysics See Seager et al., 2010; Smith and Kirnbaum, 2008

32. Changed Wind Changed Wind Changed Mountain Precipitation Changed Mountain Precipitation Changed Streamflow Differential Heating Cascading Changes

33. Is missing the effect of mountains on precipitation important?

34. Adaptation Choices

35. Regonda et al, 2005 see also Mote et al, 2005  April 1 SWE (cm) (1950-1999) - + Historical April 1 Snowpack (SWE)

36. Sensitivity of April 1 SWE Mote et al., 2005 See also Mote, 2006

37. Luce et al. (in review) Loss in April 1 SWE with 3°C increase - SNOTEL

38. Stewart et al., 2004, 2005

39. Salmon R nr Salmon Luce and Holden, 2009

40. Annual Runoff Change (1980s->2090s, A1B) IPCC AR4 SYR 3.5 Color where > 66% agreement in sign Stipled where > 90% agreement in sign

41. MF Boise River Modeled Differences 1990-2080 VIC Modeled Flow Changes

42. MF Boise River Predicted Change 1990-2080 VIC Modeled Flow Changes

44. Kormos, in prep

47. Temperature Runoff Timing Fire Extent Burned Area Sensitivity Westerling et al., 2006, 2011

48. Temperature Precipitation Runoff Timing Fire Extent Annual Runoff Annual Runoff Burned Area Sensitivity Holden et al., 2012

49. Temperature Precipitation Runoff Timing Fire Extent Annual Runoff Annual Runoff Burned Area Sensitivity  = 0.53 q = 0.17 q = 0.49 Holden et al., 2012

50. 1972-2003 large forest fires For years with early snowmelt Westerling et al, 2006

51. Fires on National Forests 2001-2007

52. Temperature Sensitivity Apr 1 SWEPrecipitation Sensitivity Apr 1 SWE Luce et al. (in review)

53. Summary Mountain precipitation has declined in Idaho. ‘Low’ elevation precipitation has shown no trend over the same period. Knowledge of the trend is essential for understanding historical snow and ecology changes and sensitivity. Insights from the trend may be informative for assessing future changes in precipitation.