The Impact of Orographic Precipitation on the Form of Mountain Ranges Alison Anders Earth and Space Sciences Dale Durran Atmospheric Sciences Gerard Roe Earth and Space Sciences University of Washington, Seattle, WA, USA

Do mountains and mountain weather co-evolve? Gyala Peri (7150 m) from the Po-TsangPo River, Tibet Thanks to Noah Finnegan

Erosion by Rivers Shapes Mountain Landscapes Queets basin, Olympic Mountains Washington, USA Channel network sets landscape relief Elwha River, Olympic Mountains, Washington, USA Hills are at the critical slope and fail as rivers erode

Stream Power Model of River Incision Erosion balances uplift

Stream Power Model of River Incision Typical River Channel Profile Distance (km) Elevation (m) Steep Upper Section Low Discharge Gentle Lower Section High Discharge

Stream Power Model of River Incision Distance (km) Elevation (m)   Q*S Erosion Rate is Proportional to Discharge times Slope

Precipitation Patterns Can Influence Topography Patterns persist for the response time of the system; at the scale of ~10 km, this is ~100,000 years  Q/Q   S/S

Range-Scale Impacts: Olympic Mountains, Washington, USA Elevation ~ 0 – 2400mPrecipitation ~850 – 5000 mm Low S, High Q

Range-Scale Impacts: Olympic Mountains, Washington, USA Elevation ~ 0 – 2400mPrecipitation ~850 – 5000 mm High S, Low Q

Sub-Range Scale Variability How do precipitation patterns and topography compare at small scales (~10 km)? MM5 run by UW researchers for forecasting precipitation at a 4km resolution 2 years of archived precipitation forecasts Simple Ice Scheme (Dudhia, 1989)

MM5 Annual Precipitation

MM5 Intense Storm Precipitation

Conclusions Storm Events Seasonal Totals Annual Totals In the Olympics, MM5 precipitation is consistently modulated by topography

Conclusions Simulated Precipitation is Greater on Ridges than in Valleys Simple Model Predicts Ridges are Lower and More Gently Sloping than with Uniform Precipitation

Further Work Field validation of precipitation pattern

Further Work Landscape evolution modeling CASCADE landscape evolution model, courtesy of Jean Braun Tectonic Uplift

Atmospheric Issues High spatial resolution precipitation patterns Interactions between topography and precipitation Stability of precipitation patterns through glacial-interglacial climate cycles

Mountain Weather and Mountains Co-evolve

Further Work Other Mountain Ranges European Alps Precipitation Gauge Climatology Frei and Schär, 1998

Further Work Other Mountain Ranges Himalaya TRMM Satellite PR Climatology