shoneswa

Environment Canada has studied this alleged effect. They have not been able to find an appreciable link between cooling rates (for humans exposed to the air) of relatively humid cold air and relatively dry cold air. There have been many supposed factors put forward in this forum that Environment Canada has ruled out as contributing to the phenomenon. First: evaporation is not a factor. Water vapour is already a gas; it doesn't need more energy to evaporate. Second: condensation is not a factor. The human skin surface is warmer than winter air, therefor water vapour will not condense on the skin. As for heat capacity, thermal conductivity etc., these are atmospheric variables that do change in different conditions. However, these variable have not been proven to account for the significant "wet cold" phenomenon many people claim to exist. So what causes it? So far, nothing has been proven, but there are a few good guesses that have been put forward. 1) In many areas during the winter, high humidity conditions often co-exist with some kind of precipitation. Any kind of liquid water (mist, fog whatever) coming in contact with the skin, in conjunction with cold temps is obviously going to feel cold. This is a no-brainer, but it is important to stress the different effects of water vapour and liquid water. 2) Probably most important: in the winter, high humidity almost always occurs during overcast conditions. Under heavy cloud cover, the earth's surface receives only diffuse sunlight. In these conditions, a person is not likely feel the radiant heat of the sun. Even in the winter and at high latitudes, direct sunlight can warm surfaces on which it shines. Even on the Canadian prairie, during a January cold snap, where temps can drop below -30 Celcius, finding a sunny spot out of the wind makes a big difference if you're trying to stay warm. Also, keep in mind that there is no scientific measurement for the "wet cold" phenomenon. There is a measurement for low temps and high wind: the wind-chill effect. This is a predictable, observable phenomenon that both people and instruments can detect. There is also a measurement for high temps and high humidity: the humidex. Again, this is predictable and observable. Canadians are weather fanatics, and to match their fervor, they have a government service (Environment Canada) that provides them with almost every possible weather fact observable. Canadians have been clamoring for a "wet cold" measurement, but Environment Canada can't find anything to give.