Alexander Buchan

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  • Alexander Buchan
    07.09.2007 15:23

    It doesn’t take a genius to realise that rowdy schoolchildren are more of an educational hindrance than help; but it took a genius to turn that particular liability to his advantage. Had it not been for a schoolteacher losing his voice shouting over his unruly pupils, then one of the great names in weather might just have spent a career brushing chalk dust from his tweeds.

    This year marks the centenary of the death of Alexander Buchan, eminent climatologist, innovative meteorologist, and the throaty tutor in question. Buchan was born in Kinneswood, Perth and Kinross, in 1829, and took up teaching after graduating from Edinburgh University. He was always a keen amateur meteorologist, and when his fragile layrynx forced him to leave the teaching profession he threw himself into the subject with gusto, becoming secretary of the Scottish Meteorological Society from 1860 until his death from pneumonia in 1907 at the age of 78.

    Under Buchan’s guidance the science of meteorology made huge strides, and it is not too much of an exaggeration when he is described as “the father of meteorology”, which is often. Until the 1860s, for example, the concept of isobars was little understood, certainly as a tool to predict the weather. A common practice until then was to plot an observation of pressure as the difference from its average but Buchan realised that it would be far more useful to calculate the sea-level pressure from all of his observations then “join the dots” to create isobars. These are, of course, the lines connecting points of equal pressure that we see every day on weather charts, and which reveal the positions of areas of high and low pressure.

    In the autumn and early winter of 1863, Buchan constructed a series of 18 charts through which he could follow the development and movement of weather systems across Europe. As these charts also included observations of wind speed and direction, he was further able to formulate the simple but utterly fundamental rules that winds blow anti-clockwise around an area of low pressure in the Northern Hemisphere, and that wind speed is proportional to the closeness of the isobars (the “barometric gradient”).

    These discoveries allowed Buchan to be the first to attempt to forecast future weather conditions, and were published in his “Handy Book of Meteorology” in 1868, alongside his investigations into the trajectory and speed of movement of depressions and their relative temperatures patterns. Later, he produced some of his most influential work: “The Mean Pressure of the Atmosphere and the Prevailing Winds over the Globe for the Months and for the Year”, thus portraying atmospheric circulations on charts that have changed little since.

    Buchan is also known for his detailed understanding of the climatology of the British Isles, collating and refining maps of average pressure, rainfall and temperature for the whole country. His work in climatology led him to what might be his most well-known postulation – “Buchan Spells”. These are theoretical interruptions (warm or cold) in the putatively smooth annual transition of temperatures, attributed to changing pressure patterns at certain specific times of year. For example, the first Buchan Cold Spell is supposed to be in the week before Valentine’s Day; the next is around the second week of April. The first Buchan Warm Spell is in the second week of July.

    Meteorologists now believe that weather patterns are less strictly defined and the atmosphere rather more complex. Ever the visionary, though, Buchan had himself declared that precise dates could vary from year to year, and that such changes were not observed every year.

    Weather professionals from all over the world are currently foregathered at the Royal Meteorological Society’s annual conference in Edinburgh – a very deliberate homage to one of the founders of their science and the city where he studied.

    By: Stephen Davenport