precipitation in the olympic peninsula of washington state robert houze and socorro medina...
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Precipitation in the Olympic Peninsula of Washington State
Robert Houze and Socorro MedinaDepartment of Atmospheric Sciences
University of Washington
Cold-Season Algorithm GV meeting, Fort Collins, 9 Nov 2009
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
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
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)
Maximum
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 km
See this full range in individual storms!
Fre
quen
cy o
f oc
curr
ence
0°C level Plot provided by Justin Minder
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
Resources and experience in the region
• 2001: IMPROVE field experiment (Stoelinga et al. 2003)
Coastline
• 2004-2008: Detailed observing network across a southwestern Olympics ridge (Minder et al. 2008)
Resources and experience in the region
Detailed gauge network
SNOTELRAWS sitesCOOP siteAnemometersDisdrometers
Resources and experience in the region
• 2009: NOAA Mobile Atmospheric River Monitoring System in Westport
Time
Hei
ght
Hei
ght
Signal-to-noise ratio
Radialvelocity
Data from vertically-pointing S-band radar
Resources and experience in the region
• 2012: NWS Coastal radar expected to be in place
Dark gray areas indicate regions where the 0.5° elevation scans are blocked
Example of Olympic Mountain slopes views from coastal radar
Current radar coverage
Radar coverage with coastal radar
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 = 4 kmdx = 36 km
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 resolution will be available shortly!
Resources and experience in the region
• Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003)
Verified by gauges: Minder et al. 2008
Long period of continuous mesoscale simulations provides model climatologye.g., 5-yr MM5 Nov-Jan precipitation climatology (mm)
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 theprecipitation accumulated in a 3 h period > 0.1in
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
Possible field experiment configuration
NPOL would have an unimpeded view of the Quinault valley and the Olympic mountains
Coastal Radar
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
Acknowledgment
This research was supported by NASA grant NNX07AD59G and NSF grant ATM-08205586