Monday, April 30, 2007

Still ice in Alberta!

By William Tuthill
Hey guys!
This is a report from Alberta where the spring ice sailing season is still going strong. It often stays good until Victoria Day weekend [that would be Memorial Day in the U.S.]!

What I like about this report is that it shows an in depth understanding of the factors that influence sailing conditions.

We all understand them in our own way, but THIS is well said.

By Barney Kenney

I am currently trying out a new method for making skis. If it works well and is economic, I may try selling a few. My preference is still to license the technology.

I was out at Spray again yesterday in strong gusty winds. Conditions were slushy because there was a snow/rain fall the night before. Normally the surface is fast and dry. Here's some of the physics.

The +15 C is produced by Chinook winds during the day. Westerly flow of warm moist Pacific air is forced upslope on the west side of the Rockies which causes rain and releases latent heat to the air. The downslope flow on the east side is therefore hotter and drier than at the same altitude on the west side. Often much hotter and drier.

Melt water produced by the warm dry wind either evaporates immediately or drains vertically along the candle boundaries and keeps the surface dry. (It is this vertical drainage that actually causes the ice to candle). Best time of year for ice sailing!

When it is clear, stability produced by back radiation decouples the surface from the westerly flow aloft at night. The surface wind stops and the temperature falls to below zero overnight. This helps to tighten everything up.

There is still a danger factor, however, because the ice sheet may be eroding from below by heat transported by baroclinic currents and stream inflows; the later you sail into spring, the more care is required.

It helps to know what you're doing, what to look for, and where not to go. We carry ice picks and drill test holes daily. It also helps if you have a board that can sail on water. Even then, one occasionally gets wet - but that's another story.

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