precipitation in the olympic peninsula of washington state robert houze and socorro medina...

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