Weather Forecasting Methods
Modern weather forecasting owes its existence to the invention of many recording weather instruments, such as the barometer, hygrometer, weather balloon, and radar. Yet, three major technological developments in particular have led weather forecasting from its days of inception to its current status: the development of instant communications beginning in the late 1800s, remote sensing devices starting in the early 1900s, and computers in the late 1900s.
Weather recording instruments date from the fifteenth century when Leonardo da Vinci invented the hygrometer, an instrument to measure atmospheric humidity. About 1643, Evangelista Torricelli created the barometer to measure air pressure differences. These instruments were improved upon in the eighteenth century by Frenchman Jean Andre Deluc (1727–1817), and have been refined numerous times since then. Weather information has long been displayed in map form. In 1686, English astronomer Edmond Halley (1656–1742) drafted a map to explain regular winds, tradewinds, and monsoons. Over 200 years later, in 1863, French astronomer Edme Hippolyte Marie-Davy (1820–1893) published the first isobar maps, which depicted barometric pressure differences. Weather data allowed scientists to try to forecast weather. The United States Weather Service, established in 1870 under the supervision of Cleveland Abbe, unified communications and forecasting. Telegraph networks made it possible to collect and disseminate weather reports and predictions. By the turn of the twentieth century, the telephone and radio further increased meteorologists' ability to collect and exchange information. Remote sensing, the ability to collect information from unmanned sources, originated with the invention of the weather balloon by Frenchman Leon Teisserenc de Bort (1855–1913). Designed to make simple preflight tests of wind patterns, balloons were eventually used as complete floating weather stations with the addition of a radio transmitter to the balloon's instruments. Many scientists added to the pool of meteorological knowledge, including Englishman Ralph Abercromby who, in his 1887 book, Weather, depicted a model of a depression that was used for many years.
During World War I, the father-son team of Vilhelm Bjerknes (1862–1951) and Jacob Bjerknes (1897–1975) organized a nationwide weather-observing system in their native Norway. With the available data they formulated the theory of polar fronts: The atmosphere is made up of cold air masses near the poles and warm tropical air masses, and fronts exist where these air masses meet. In the 1940s, Englishman R. C. Sutcliffe and Swede S. Peterssen developed three-dimensional analysis and forecasting methods. American military pilots flying above the Pacific during World War II discovered a strong stream of air rapidly flowing from west to east, which became known as the jet stream. The development of radar, rockets, and satellites greatly improved data collection. Weather radar first came into use in the United States in 1949 with the efforts of Horace Byers (1906–1998) and R. R. Braham. Conventional weather radar shows precipitation location and intensity.
In the 1990s, the more advanced Doppler radar, which can continuously measure wind speed in addition to precipitation location and intensity, came into wide use. Using mathematical models to automatically analyze data, calculators and computers gave meteorologists the ability to process large amounts of data and to make complex calculations quickly. Today the integration of communications, remote sensing, and computer systems makes it possible to predict the weather almost simultaneously. Weather satellites, the first launched in 1960, can now produce sequence photography showing cloud and frontal movements, water-vapor concentrations, and temperature changes. With the new radar and computer enhancement, such as coloration, professionals and untrained viewers can better visualize weather information and use it in their daily lives.
Air Masses and Fronts; El Niño and La Nina Phenomena; Isobars; Meteorology
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