Saturday, March 8, 2008

Snow sublimation?

As I was riding the chairlift the other day, I had a brief, but revealing conversation with another skier when I started to say that snow sublimation played a big role in its disappearance. Like most folks, she had no clue what snow sublimation was all about and after researching the subject, I realized that I was almost as ignorant about it. So what is there to know about snow sublimation? My understanding was that when conditions were met, namely when outside temperatures, exposition to sun (orientation), wind speed, relative humidity, latitude and altitude were taken into account, each component had an effect on the rate of snow sublimation. But first, what’s sublimation? It is a naturally occurring process in which solid ice and snow turn into vapor without passing through the usual liquid stage. My contention was that, when all conditions were favorable, more snow could disappear through sublimation than through ordinary melting. So far, however, I haven’t been able to find much substantiation to my claim and my point is mostly based on personal observation. I have read that when high altitude (10,000 feet) and low humidity are combined, up to 50% of snow ablation is attributed to sublimation, while under that altitude, traditional snowmelt generally dominates.
In the Alps, there’s a dry and warm wind called “foehn” that will speed up sublimation. I’ve seen that wind at work, and its influence on the snowpack can be devastating. So my question is this; is there someone who can give me some reliable numbers that could support my theories?