Mid-Mountain Clouds at Whistler During the Vancouver 2010 Winter Olympics and Paralympics

• Published in: Pure and applied geophysics 2014, Vol.171 (1-2), p.157-183
• Main Authors: Mo, Ruping, Joe, Paul, Isaac, George A., Gultepe, Ismail, Rasmussen, Roy, Milbrandt, Jason, McTaggart-Cowan, Ron, Mailhot, Jocelyn, Brugman, Melinda, Smith, Trevor, Scott, Bill
• Format: Article
• Language: English
• Subjects: Adiabatic flow; Atmospheric models; Clouds; Drying; Earth and Environmental Science; Earth Sciences; Evaporative; Geophysics/Geodesy; Meteorology; Mountains; Olympic games; Paralympic Games; Subsidence; Temperature inversions; Weather forecasting; Whistlers; Winter
• ISSN: 0033-4553; 1420-9136
• DOI: 10.1007/s00024-012-0540-2

A comprehensive study of mid-mountain clouds and their impacts on the Vancouver 2010 Winter Olympics and Paralympics is presented. Mid-mountain clouds were frequently present on the Whistler alpine venue, as identified in an extensive archive of webcam images over a 45-day period from February 5 to March 21, 2010. These clouds posed serious forecast challenges and had significant impacts on some Olympic and Paralympic alpine skiing competitions. Under fair weather conditions, a diurnal upslope (anabatic) flow can work in concert with a diurnal temperature inversion aloft to produce a localized phenomenon known as “Harvey’s Cloud” at Whistler. Two detailed case studies in this paper suggest that mid-mountain clouds can also develop in the area as a result of a moist valley flow interacting with a downslope flow descending from the mountaintop. A southerly inflow through the Sea-to-Sky corridor can be channeled by the local topography into a westerly upslope flow toward Whistler Mountain, resulting in orographic clouds on the alpine venue. Under favorable circumstances, these clouds are trapped to the mid-mountain zone by the leeward subsidence of an elevated southerly flow. The presence of the downslope subsidence was manifested by a distinguished dry layer observed on the top of the mid-mountain clouds in both cases. It is the subsidence-induced adiabatic warming that imposes a strong buoyant suppression to trap the mid-mountain cloud. On the other hand, the subsidence-induced dry layer has the potential to trigger evaporative instability to periodically breakup the mid-mountain cloud.