The capricious climate

Palmen in Ascona

Central Switzerland is not only the cradle of the Swiss Confederation. It is not only the heart of extensive drainage system whose ramifications spread over large parts of Europe. It is an area where very diverse climates meet and overlap. Relatively mild and moist maritime air masses flow across form the west. But, under the influence of the continental climate of the Hinterland, a drier, colder wind blows from the east, warming up noticeably in the course of the summer. A cold polar wind, the notorious “Black Breeze”, comes from the north, a moist wind, the “Föhn”, from the south. Thus Switzerland enjoys a  transitions in the mountains. The annual rainfall on the Jungfrau is 4,000 mm, and yet a few kilometres away, in Valais, it  is only 500 mm Considering the latitude, the climate is rough. Three quarters of Switzerland has an annual rainfall of more than a metre. the very rainy area round St. Gothard is popularly known as “Switzerland’s chamber pot” – not very flattering for a region of such strategic and historical importance. The higher you go, the it rains or snows. On the Säntis it snows on about 150 days a year. The climate is varied. Near La Brévine, in the Neuchâtel Jura , a veritable Swiss Siberia, temperatures can sink to minus 30 degrees  C in winter. At the same time, palms grow in Montreux and numerous tropical plants flourish on the islands of Lake Maggiore. And yet the mountains are not always damp misty; above the clouds the air is generally quite dry. While the lowlands and valleys are wrapped in a thick, gloomy mantle Of mist in the winter, which can drive even the greatest optimist to despair, high in the mountains it is often fine, and even hot, and tourists can sunbathe as if they were on a Mediterranean or Caribbean beach. Nevertheless, with their large number of rainy days and rather frequent cloud, the mountains are basically under the influence of a maritime climate. The Atlantic is a source of moist winds which cross the Continent from west to east. When they encounter the Jura or the Alps, the tamp air masses ascend, cool down, and lose most of their moisture in the from of more or less heavy rain. The south side of the range escapes the rain; it is a favoured, relative dry area. The south wind has a similar effect. In this case, the rain falls mainly on the southern slopes of the Alps on each side of the Rhine – Rhôhne trench The central valley of Valais thus remains rather dry, with only 500 to 800 mm of rain per year. The winds play an essential part even in the regional climate. The eastern slopes of the mountains are warmed by the sun in the early morning. The air rises, passes the high peaks, and cumulus from. This upward movement of air in the mountains draws a current of air down into the valleys powerful enough to bend and distort the tall poplars. During the night the process is reversed. The colder, heavier air of the heights sinks into the valleys. In reaction to this, the mountain breeze now up the valley – in the opposite direction to the morning breeze. The föhn wind is still a bit of a mystery to the meteorologists. At one time it was believed that it came from the Sahara. But now we know that this warm, moist wind comes from the Mediterranean area, although it is sometimes accompanied by Sahara currents; these may carry reddish – coloured sand with them, traces of which can then be seen on the Alpine snowfields. The föhn wind passes through several phases on its way northwards. In the southern Alps it releases its moisture in heavy falls of rain which transform the streams into torrents. Then it crosses the mountain chain, continues northwards, and blows across the plateau. It dries out the air, disperses mist, and miraculously clears the atmosphere. If a few clods still persist around the northern peaks are surrounded by a “föhn window”, a bright, sunny zone. Föhn is both beneficial and harmful. It favours the growth of plants that need warmth, like vines, maize, and chestnuts. But when it is in a gusty mood it destroy woods and houses and even cause fires. Föhn precipitates sudden thaws of the snow. resulting in floods, sometimes of catastrophic proportions. Finally many people living in areas affected by the föhn fear the wind because it can cause sleeplessness, migraines, and exhaustion.