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Precipitation in the Olympic Peninsula of Washington State

Precipitation in the Olympic Peninsula of Washington State. Robert Houze and Socorro Medina Department of Atmospheric Sciences University of Washington. Cold-Season Algorithm GV meeting, Fort Collins, 9 Nov 2009. The Olympic Peninsula is a natural “precipitation laboratory”.

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Precipitation in the Olympic Peninsula of Washington State

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  1. Precipitation in the Olympic Peninsula of Washington State Robert Houze and Socorro Medina Department of Atmospheric Sciences University of Washington Cold-Season Algorithm GV meeting, Fort Collins, 9 Nov 2009

  2. The Olympic Peninsula is a natural “precipitation laboratory” • Persistent southwesterly flow during the winter provides a reliable source of moisture • Extremely large precipitation accumulation produced as the moist SWly flow impinges on coastal terrain • Low 0ºC level rain at low elevations, snow at higher levels

  3. The Olympic Peninsula is a natural “precipitation laboratory” • Persistent southwesterly flow during the winter provides a reliable source of moisture NCEP long-term mean sea level pressure (mb) for winter (December to January) and topography

  4. Maximum The Olympic Peninsula is a natural “precipitation laboratory” • Extremely large precipitation accumulation produced as the moist SWly flow impinges on coastal terrain Annual average precipitation (PRISM)

  5. Frequency of occurrence 0°C level The Olympic Peninsula is a natural “precipitation laboratory” • Low 0ºC level  rain at low elevations, snow at higher ones Distribution of Nov-Jan 0°C level for flow that is onshore and moist at low levels (KUIL sounding)Mean 0°C level during storms = 1.5 kmSee this full range in individual storms! Plot provided by Justin Minder

  6. Resources and experience in the region • 1965-2000: Cascade Project, CYCLES, COAST • 2001: IMPROVE field experiment • 2004-2008: Detailed observing network across a southwestern Olympics ridge • 2009: NOAA Mobile Atmospheric River Monitoring System in Westport • 2012: NWS Coastal radar expected to be in place • Ongoing: Regional Environmental Prediction

  7. Resources and experience in the region • 2001: IMPROVE field experiment (Stoelinga et al. 2003) Coastline 

  8. Detailed gauge network SNOTEL RAWS sites COOP site Anemometers Disdrometers Resources and experience in the region • 2004-2008: Detailed observing network across a southwestern Olympics ridge (Minder et al. 2008)

  9. Resources and experience in the region • 2009: NOAA Mobile Atmospheric River Monitoring System in Westport Data from vertically-pointing S-band radar Signal-to- noise ratio Height Radial velocity Height Time

  10. Resources and experience in the region • 2012: NWS Coastal radar expected to be in place Example of Olympic Mountain slopes views from coastal radar Dark gray areas indicate regions where the 0.5° elevation scans are blocked Current radar coverage Radar coverage with coastal radar

  11. Resources and experience in the region • Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Real-time mesoscale numerical simulations dx = 36 km dx = 4 km

  12. Resources and experience in the region • Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Real-time simulations with 1.33 km spatial resolutionwill be available shortly!

  13. Resources and experience in the region • Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Long period of continuous mesoscale simulations provides model climatology e.g., 5-yr MM5 Nov-Jan precipitation climatology (mm) Verified by gauges: Minder et al. 2008

  14. Resources and experience in the region • Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Ensemble forecasting  probabilistic information e.g., probability that the precipitation accumulated in a 3 h period > 0.1in

  15. Resources and experience in the region • Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Hydrological prediction: Mesoscale numerical output drives a distributed hydrological model  basin streamflow forecast

  16. Coastal Radar Possible field experiment configuration NPOL would have an unimpeded view of the Quinault valley and the Olympic mountains

  17. Conclusions • The Olympic Peninsula is an ideal natural precipitation laboratory given: • Persistence of moist flow, complex terrain, huge precipitation amounts, and low 0°C level • The existing and planned resources and the past experience in this region provide a strong framework for a field campaign

  18. Acknowledgment This research was supported by NASA grant NNX07AD59G and NSF grant ATM-08205586

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