Alexander Buchan, Scottish meteorologist, was educated at the Free Church Normal School in Edinburgh. After qualifying he worked as a teacher at Free Church schools in various towns from 1848 to 1860, but in 1858 took part in an expedition to the Alps by Professor Balfour of the University of Edinburgh. He subsequently studied at that university, obtaining the degree Master of Arts (MA) in 1864. He had an early interest in field botany and was president of the Edinburth Botanic Society during 1870-1871. However, in 1860 he became secretary of the Scottish Meteorological Society and from that time devoted most of his life to the Society and meteorology in general. His work involved, among others, inspecting the instruments and procedures used at meteorological stations. In 1864 he furthermore became the first editor of the Journal of the Scottish Meteorological Society, as well as its main contributor. From 1878 to 1906 he was also curator of the library of the Royal Society of Edinburgh. He was awarded an honorary Doctor of Laws degree in Glasgow in 1887, and was elected a Fellow of the Royal Society of Edinburgh in 1869 and a Fellow of the Royal Society of London in 1898.
Buchan's textbook A handy book of meteorology (Edinburgh, 1867, 204p) was used all over the world. He wrote another Introductory text-book of meteorology (Edinburgh, 1871, 218p) and more than 80 papers on all aspects of meteorology and climatology. Most of his papers were published in the Journal of the Scottish Meteorological Society and the Transactions of the Royal Society of Edinburgh. However, his greatest achievement was the publication of the first map of mean atmospheric pressure and winds over the globe for individual months and the year as a whole, in the Transactions of the Royal Society of Edinburgh in 1869. In 1889 he produced a Report on atmospheric circulation based on the observations made on board HMS Challenger during the years 1873-1876. In 1895 this was followed by a report on oceanic circulation, also based on the observations of the Challenger Expedition.
Early in his career as a meteorologist Buchan pointed out that the practice of determining height above sea level from atmospheric pressure in the interior of southern Africa was subject to error, because the pressure varies systematically over a day and over the seasons. This argument formed part of his more general discussion of the problem of finding height from atmospheric pressure, in the Proceedings of the Royal Geographical Society for 1868-1869. In 1872 he and J.F. von Hann* published tables of mean temperature and rainfall in South Africa in the Zeitschrift der Österlische Gesellschaft für Meteorologie. However, his main contribution to South African meteorology came when the Meteorological Commission of the Cape of Good Hope asked him in 1896 to review South African rainfall data for the years 1885 to 1894. His report, A discussion of the rainfall of South Africa during the ten years, 1885-94, with 16 maps and rainfall tables, was published in Cape Town in 1897. He also published a brief paper on this work in Nature in 1899. The data pertained mainly to coastal stations, with scanty information from the summer rainfall regions in the interior. Nonetheless Buchan presented one of the early theories to explain the seasonal distribution of the rainfall over southern Africa, based on the geographical distribution of atmospheric pressure and temperature: Low pressure over the interior in summer causes moist air to flow in from the coast and produce rain. But the permanent anticyclone over the Atlantic Ocean close to the west coast does not allow the out-blowing winds to traverse much of the ocean before reaching land, hence these winds are dry, while those from the Indian Ocean are moist. Thus the eastern regions of the country receive most rain. In winter a high pressure system develops over the interior, preventing the rain winds from reaching there. However, the anticyclone to the west of Cape Town causes moist air to flow over the south-west Cape at that time, thus producing a winter rainfall season there. The importance of Buchan's theory lies in the fact that it initiated the idea of permanent seasonal pressure systems over the sub-continent - an idea that has been widely accepted.
Buchan's report elicited rather severe criticism from D.E. Hutchins*, who discussed it in the Agricultural Journal of the Cape Colony (Vol. 11, pp. 701-710) in 1897.