IN MANY parts of the world there are winds with marked individual characteristics that blow from a particular direction with such persistent regularity that they have been given names by the local population. The cold mistral of the Rhone Valley is a case in point so too is the dry foehn of the Swiss Alpine valleys, and the warm chinook that blows down the eastern slopes of the Rocky Mountains in north America.
The Russians have their local winds as well. The buran is a strong and bitterly cold, northeasterly that blows across Siberia in winter, raising irregularities or wave like formations on the surface of the snow that the Russians call sastruga. This latter term has become one of the many words imported into English, and used by skiers to describe the characteristics of the snow at any given time. Others, equally graphic and often almost onomatopoeic, are windslab breakable crust and crude sugar, corn and glop and fluff cement and boilerplate.
Fallen show changes in consistency with time. New flakes have tiny pockets of air trapped between them, and act as an insulating blanket to protect underlying plants from the worst ravages of frost. Older snow settles and becomes dense as the loose pointed crystals are transformed into small round grains as time goes by the spaces between the grains become smaller and smaller with compaction, and if enough time elapses the covering may change to solid glacial ice.
The process of skiing on freshly fallen snow is facilitated by the friction of the ski sliding across the surface. The friction melts the ice crystals in immediate contact with the ski - almost instantly, and the water thus produced acts as a lubricant to facilitate further sliding motion. In extremely cold conditions, however, as Arctic explorers have sometimes found to their surprise, skiing becomes difficult or even impossible at a temperature of say 40" below zero, it is too cold for instant melting to take place, and the skis, rather than melting the points of the crystals to make them slippery, simply roll them over and over. The result is a harsh, dry surface more like sand than snow.
Oddly enough, very little snow falls in these very cold Arctic regions. The precipitation in these parts falls in the form of individual ice crystals, and at a rate equivalent to less than 2 inches per year - only slightly more than falls on the Sahara Desert. The vast ice cap continues to grow, of course, but only very, very slowly over millions and millions of years.