In night temperature, but in night temperature only, the passing from summer to winter, upwards of 9,000 feet may indeed be said to have fully taken place long before the end of the year. This passage is marked by the regular freezing at night of all moisture, and by the regular freezing over of all surfaces on which moisture is deposited by day. Still, the first fall of a general layer of snow, which will last throughout the winter on the high levels, may be much delayed. Till that first layer has covered the high ground, the ski-runner’s winter has not begun.
THE WILDSTRUBEL HUT.
To face p. 21.
The first general snowfall, if it mark the beginning of the ski-runner’s winter, does not yet mark the setting in of the ski-running season. For a time, which may extend from November to near the end of December, moisture proceeding from the atmosphere, that is rain and vapours (warm, damp winds), is not without effect at the altitudes which we are considering. Such a damp condition of the air and any risk of rain are quite inconsistent with ski-running. But everybody should know that if such risks must be taken throughout the winter by a ski-runner residing, for instance, at the altitude of Grindelwald, they may practically be neglected by a sportsman whose field of exercise is that to which the Swiss Alpine Club huts afford access.
There, from Christmas to early Easter, the only atmospheric obstacle consists of snowstorms, in which the wind alone is an enemy, while the snow entails an improvement in the conditions of sport each time it falls. The November and December snowfalls prepare the ground for running, and running at those heights is neither safe nor perfect as long as the process goes on. In January and February any snowfall simply improves the floor or keeps up its good condition. It may be taken that during these months the atmosphere is absolutely dry from Tyrol to Mont Blanc above 8,000 feet, and that a so-called wet wind will convey only dry snow. Any moisture or water one may detect will be caused by the heat of the sun melting the ice or the snow. It is a drying, not a wetting, process; it leaves the rocks facing south, south-east, and south-west beautifully dry, and completely clears them, by rapid evaporation, of the early winter snows or of any casual midwinter fall accompanying a storm of wind.
Such are the atmospheric reasons which help to determine the proper ski-running months in the High Alps.
There are others which are still of a meteorological description, but which are connected mainly with the temperature. We shall begin by giving our thought a paradoxical expression as follows: it is a mistake to talk of winter at all in connection with the High Alps. According to the time of year, the weather in the Alps is subjected to general rain conditions or to general snow conditions. Under snow conditions the thermometer falls under zero Centigrade, and the temperature of the air may range from zero to a very low reading; but the sun is extremely powerful, its force is intensified by the reflection from the snow surface. The temperature of the air in the shade is therefore no clue to the temperature of material surfaces exposed to the rays of the sun. The human frame, under suitable conditions of clothing and exercise, feels, and actually is, quite warm in the sun, a violent wind being required to approximate the subjective sensations of the body to those usually associated with a cold, damp, and biting winter’s day.
This is a general characteristic of the Alpine winter, to which must be added an occasional, though perfectly regular, feature, namely, that the Alps may offer, and do offer every winter, instances of inverted temperature. This name is given to periods which may extend over several days at a stretch, and which are repeated several times during the winter months. These are periods during which the constant temperature of the air—that is, the average temperature by night and by day in the shade—is higher upon the heights than in the plains and valleys.