METEOROLOGY, the science of the atmosphere (Gr. merhopa and ?kayos, the science of things in the air). In its widest sense the term includes the study of weather, climate, optical phenomena in the atmosphere and atmospheric electricity.
The beginnings of the study of weather are lost in antiquity. Some of the earliest writings extant contain fragmentary refer ences to weather phenomena, but the earliest known effort at systematic discussion was the Meteorologica of Aristotle B.C.). Theophrastus, a pupil of Aristotle, wrote treatises on winds and on weather signs. Then for two thousand years meteorology stood still.
The Beginning of Meteorology as an Exact Science.—Ad vances were made with the invention of the thermometer (see HEAT) by Galileo in 1607, the invention of the barometer (q.v.) by Torricelli in 1643, the discovery of Boyle's law (q.v.) in 1659, and the invention of the wheel barometer by Hooke about 167o. Halley (1656-1742) attempted to explain the trade winds as a direct consequence of the distribution of solar radiation over the earth, but the true explanation was given by George Hadley in 1735, in a paper in which for the first time allowance was made for the effect of the rotation of the earth. In 1742 Celsius invented a Centigrade thermometer. Later de Saussure (1740-1799) Per fected the thermometer and hygrometer, and showed that damp air is lighter than dry air at the same temperature and pressure. The true nature of atmospheric air was established by Lavoisier in 1783, and the laws of pressure of water-vapour in air were given by Dalton in 1800. Dalton also wrote an epoch-making paper on the effects of rarefaction and condensation, which laid the foundation of modern physical meteorology.
The First Weather Charts and Systematic Observations. —The Chevalier de Lamarck (1774-1829) working with Laplace, Lavoisier, and others established a reseau of observing stations, and published a series of Annuaires Meteorologiques from 1800 to 1825. In 182o Brandes produced a series of daily weather charts, one for each day of the year 1783, and later published charts of the great storms of 182o, 1821 and 2823. He explained these
storms as due to barometric depressions advancing from west to east over the earth's surface. In America, Espy (1785-186o) carried out similar researches, and published a book Philosophy of Storms (Boston 1841). Espy established a service of daily synchronous observations and studied in detail the behaviour of depressions. The work of Lamarck, Brandes, Espy, Loomis, and others led to the establishment of networks of stations in several countries within the years 1850-56, the Meteorological Office in London being established in 1854. International co-operation was first established by an international conference held in Brussels in 1853, and was put on a sound basis by an international congress in Vienna in 1873. The exchange of information was at first by telegraph, later by wireless telegraphy.
Small free rubber balloons carrying self recording instruments (Sounding balloons) were first used by Hermite and Besancon in 1893, and in 1899-1902 Teisserenc de Bort and Assmann estab lished the fact that above a height varying from 18 km. at the Equator to about II km. in latitude 5o°, and to 6 km. or less at the poles, the temperature remained sensibly constant with height. (See section on Vertical Distribution of Meteorological Ele ments.) Upper air temperatures and humidities are now obtained daily from wet and dry bulb thermometers placed on the wing struts of aeroplanes.