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High and Dry: Declining Precipitation in the Mountains of the Pacific Northwest

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. Luce and Holden, 2009. Declining PNW Streamflows.

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High and Dry: Declining Precipitation in the Mountains of the Pacific Northwest

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  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

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

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

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

  5. 25th – Dry Years 75th – Wet Years Mean 50th Luce and Holden, 2009

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

  7. Why? P E

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

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

  10. Insufficient Additional Energy Available to Evaporate Water 1.8 W/m2 4.2 W/m2

  11. Precipitation Gage Watershed Max Mean Min

  12. Orographic Precipitation Kirshbaum and Smith, 2008

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

  14. Precipitation Correlation with Regional Westerly Wind Speed

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

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

  17. Why did the wind slow?

  18. Influence of Climate Modes on Wind U700=f(MEI,PNA,PDO), R2=0.37, P<0.001

  19. PDO

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

  21. Trends and Future Predictions

  22. Why would warming slow the westerlies?

  23. Future Changes in Pressure

  24. Historical Trends in Nov-Mar 500hPa Height

  25. Interannual Variations in Nov-Mar Westerlies

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

  27. 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

  28. Differential Heating Cascading Changes Changed Pressure Distribution Changed Wind Changed Mountain Precipitation Changed Streamflow

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

  30. Adaptation Choices

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

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

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

  34. Stewart et al., 2004, 2005

  35. Salmon R nr Salmon Luce and Holden, 2009

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

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

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

  39. Kormos, in prep

  40. Kormos, in prep

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

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

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

  44. 1972-2003 large forest fires For years with early snowmelt Westerling et al, 2006

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