Forecasting sun vs. shade in complex terrain for the 2010 Winter Olympic and Paralympic Games

El Niño conditions during the 2010 Vancouver Winter Olympic and Paralympic Games in Canada provided 10 mostly-sunny days at the outdoor Olympic venues. The warmth and sunshine significantly reduced snow cover at one venue and weakened the snowpack at the other two venues, much to the chagrin of the event organizers. Solar radiation affects ski racing via its effect on snow-surface friction, abrasion, and mechanical strength. Ski technicians and athletes compensate via the choice of ski and wax. For these reasons, sun vs. shade forecasts were produced for Canadian ski and snowboard teams.

A theodolite was used to survey horizon-elevation angles around full azimuth circles at 133 locations spaced roughly 150 m apart along race pistes (marked ski runs) at three Olympic venues. This survey was important for including the shadowing effects of the tall evergreen trees that border the pistes, which otherwise would not be properly accounted for if only digital elevation data was used. These data, along with the astronomical equations for solar elevation and azimuth, were used to calculate whether each survey point would be in the sun or the shade in cloudless conditions for any time and date during the Olympics. Half-hourly output was provided to ski and snowboard technicians and coaches via a graphical user interface delivered on the internet.