Scotland's Weather

Scotland lies under the zone of eddies in the northern hemisphere, and the variability of Scotland's weather owes much to their passage over the region. Whilst we cannot see the wind, its course is marked by the clouds it bears along. The eddies that sweep over Scottish skies bring air from all quarters in turn. A glance at the atlas shows that air from the west or southwest has passed over the vast Atlantic Ocean which reaches Scotland's west coast. Air from the north will have traversed the Arctic Ocean which washes the Shetlands, Orkneys and Scotland's northern coast. That from the east and south will have passed over continental Europe and perhaps crossed the North Sea before reaching Scotland's east coast. Each wind brings its own characteristic weather, according to the season. The Atlantic Ocean is always relatively warm, so moist westerly winds bring most of Scotland's rain, which falls principally on the western margins of the country. The north winds of summer cross a chilly Arctic Ocean and bring noticeably colder weather, often with light rain or showers. In winter, when parts of the northern seas are frozen, the air can be extremely cold and dry, giving remarkable visibility. Winds from the east and south, having traveled over land, can be warm and dry in summer, cold and dry in winter, although winds passing over the North Sea can pickup enough moisture to drop considerable amounts of rain or snow on Scotland's eastern counties. The amount of moisture which air can absorb as it crossed open water ~creases with its temperature. The western winds are the warmest and the most moisture-laden. As these winds reach the coast, the air must rise to cross the mountains. As air rises, it cools, the moisture condenses, clouds form, bringing heavy rain along the coast with snow at higher levels. The western part of Scotland receives around three times more precipitation than the eastern part where the air is generally drier.

The famous Scottish mist consists of cloud at ground level, formed of drops of moisture so small that they hang in the air and cling to any vegetation as individual droplets. en days when rain showers alternate with sunny periods, rainbows are a common sight. Scotland lies between latitudes of 55 degres and 61 degrees North, and while the summer days are long, the sun is never high in the sky. In winter the sun rises only a little way above the horizon and sinks again within a few hours. This low sun angle, which causes the rays of light to pass through a considerable thickness of the atmosphere, is responsible for many of the optical effects and colours of the sky and clouds which artists and visitors find so attractive.

Some passages in this anthology describe weather more extreme than we are now accustomed to. In historical times written records supplement archaeological evidence of warmth increasing from around 800 to 1300 AD, when the treeline and the limits of cultivation stood higher than they do now. Towards the end of this period, however, there are records of severe storms, flooding along low coasts and notable droughts, and a period of gradual cooling set in. These events were naturally reflected in the lives of the people, and also on the plants and animals of the region. A dreadful run of wet summers between 1313 and 1320 resulted in crop failure, with people and animals ravaged by starvation and disease. In the 1430's came a series of extremely severe winters. The long history of clan raids and cattle stealing from the lowlands must owe something to the stress of a deteriorating climate after the golden age of maximum settlement and cultivation enjoyed during the twelfth and thirteenth centuries. On various occasions between 1200 and I 800 southerly gales struck the. east coast during low tide, sweeping vast quantities of sand inland, and in several cases fertile fields or settlements were entirely buried. A notable example is the medieval town of Forvie, on the east coast of Aberdeenshire, overwhelmed in August 1413. During the 'Little Ice Age' of the sixteenth to eighteenth centuries the ocean surface northeast of Scotland was some 5 degrees cooler than now and the weather coming from that direction was markedly colder. Travellers reported permanent snow on the Cairngorms. Cold winters may be tolerable providing food supplies hold out, but late frosts which damage crops in the growing season, and low summer temperatures which prevent ripening inevitably bring famine and loss of livestock in their wake. Such disasters struck with increasing frequency and severity up to 1700.

Since then there has been a slow improvement, albeit with occasional regressions. In recent centuries people began to take advantage of winter's ice and snow The sports of skating and curling became popular whenever the weather allowed, followed more recently by ski resorts opening in parts of the Highlands which could anticipate a reasonable snow cover. These climatic changes account for some of the apparent anomalies in popular weather lore. In fact, these sayings fall into two groups: those which forecast weather, and those which forecast climate. Climatic forecasts, those sayings which predict summer rainfall from observing when species of tree come into leaf, or severity of the coming winter from the time of migration of certain birds, have little validity. But familiarity with the local topography can enable a reasonable forecast of weather within the next few hours to be made, if the wind direction, temperature and humidity are known. The observer without instruments takes information from the form and height of the clouds, and the visibility, and colour of the sky. Over hundreds, or thousands, of years, people have recorded these weather signs in the form of proverbs, such as the familiar 'red sky at night is a shepherd's delight.'. Scotland's Weather: An Illustrated Anthology.