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Mid-Mountain (a.k.a Harvey’s) Clouds at Whistler, BC, Canada

Mid-Mountain (a.k.a Harvey’s) Clouds at Whistler, BC, Canada. Ruping Mo Environment Canada. Whistler Mountain. Mid-Mountain (Harvey’s) Clouds. 1040 PST 2010-02-14. Harvey Fellowes. Mid-Mt. Clouds (Mosaic). Impact of Alpine clouds. 11 February 2010, Whistler.

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Mid-Mountain (a.k.a Harvey’s) Clouds at Whistler, BC, Canada

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  1. Mid-Mountain (a.k.a Harvey’s) Clouds at Whistler, BC, Canada Ruping Mo Environment Canada

  2. Whistler Mountain

  3. Mid-Mountain (Harvey’s) Clouds 1040 PST 2010-02-14 Harvey Fellowes

  4. Mid-Mt. Clouds(Mosaic)

  5. Impact of Alpine clouds 11 February 2010, Whistler

  6. Diurnal visibility Occurrence frequency 5 Feb – 21 Mar 2010

  7. Mid-mountain cloud 2010-02-16 1100 – 1340 PST

  8. Mid-mountain cloud Thermal impact: Thermally forcing up-slope flow interacting with inversion in the morning (Mo et al. 2012) Late-morning tendency

  9. Mid-mountain cloud 2010-02-16 1100 – 1340 PST A Case Study

  10. Mid-mountain cloud A Case Study: Morning (1000 PST, 16 Feb 2010)

  11. Mid-mountain cloud A Case Study: Afternoon (1600 PST, 16 Feb 2010)

  12. Mid-mountain cloud Whistler (WAE) Sounding

  13. Mid-mountain cloud

  14. Mid-mountain cloud Dry layer (cloud top)

  15. Model Prediction (1 km resolution) Meteograms at mid-mountain (VOL, 2010-02-16) Low visibility Cloudy No high cloud

  16. Model Prediction (1 km resolution) Meteograms at mid-mountain (VOL, 2010-02-16) Cloudy Gusty SW winds No high cloud

  17. Observation vs Prediction

  18. Observed Predicted

  19. Model Prediction 1 km resolution model Visibility forecast

  20. Model Prediction 1 km resolution model Valid at 2010-02-16 1100 PST (1900 UTC)

  21. Model Prediction 1 km resolution model Valid at 2010-02-16 1100 PST (1900 UTC) (Vertical velocity)

  22. Conceptual Model • Valley inflow drives up-slope flow and gives rise to clouds • Leeward subsidence of elevated flow traps the clouds • Late-morning tendency is thermally driven

  23. Another Case

  24. Oscillation on mountain slope 2010-02-27, 1100 – 1500 PST

  25. Oscillation on mountain slope 2010-02-27, 1100 – 1500 PST • Possible mechanisms: • Cloud-top evaporative • instability

  26. Oscillation on mountain slope 2010-02-27, 1100 – 1500 PST • Possible mechanisms: • Cloud-top evaporative • instability • Slope-flow induced • gravity waves

  27. Summary • Mid-mountain clouds at Whistler are common in Winter • Mid-Mt clouds form most frequently late in the morning • Mid-Mt clouds form under stably stratification, usually post-frontal, when moderate valley inflow prevails • Mid-Mt clouds form on the leeward slope, when weak to moderate leeward subsidence is expected • Mid-Mt clouds could experience oscillations with 1-3 hr periods • Mid-Mt clouds have significant impact on downhill skiing competitions • Demonstrate value of web cams, 1 km model

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