Meteorology - The study of the atmosphere and its phenomena.

As with most physical sciences, it is nearly impossible to determine an exact "beginning" for the science of meteorology. A distinction must be made between meteorology as a science and meteorology as a "branch of knowledge". As farmers and hunters, early man was strongly dependent upon atmospheric conditions for his existence. Although he could not adequately explain many atmospheric phenomena (a problem we still have today), a collection of weather "signs" was accumulated and handed down from generation to generation, many taking the form of what we call "folk proverbs".

The term "meteorology" seems to have originated in 340 BC when the Greek philosopher Aristotle wrote a book on natural philosophy entitled Meteorologica. This work presented the philosophical knowledge of the atmosphere at that time and included topics such as clouds and mist, rain, snow, wind, hail, lightning and thunder, and climatic changes. In addition, topics such as astronomy, geography and chemistry were also addressed. The manuscript was entitled Meteorologica because in those times, any particle which fell from the sky, or was suspended in the atmosphere, was called a meteor. Today, we distinguish between "meteors" (extraterrestrial meteoroids) and "hydrometeors" (particles of water or ice in the atmosphere).

In Meteorologica, Aristotle attempted to explain atmospheric phenomena in a philosophical manner. Although many of his claims were erroneous, it was not until the 17th century that many of Aristotle's original ideas were scientifically disproved.

Why were Aristotle's ideas about the weather unchallenged for nearly 2000 years?

The birth of meteorology as a legitimate natural science occurred near the end of the 16th century. It had become increasingly evident that the speculations of the natural philosophers were inadequate and that greater knowledge was needed to further our understanding of the atmosphere. In order to do this, instruments were needed to measure the properties of our atmosphere (i.e. temperature, moisture, pressure); instruments which had not yet been invented.

The first of these inventions was the hygrometer. The Greek philosophers seemed to understand the basics of how water circulated through the earth-atmosphere system even without instruments. However, water in its vapor state is invisible; therefore, it was the least understood. Questions concerning the properties of this "invisible water" led to the invention of a humidity-measuring instrument by the German mathematician Cardinal Nicholas de Cusa around 1450.

The second of these inventions was the thermometer. The invention was attributed to Galileo Galilei in 1593, although the exact date of its invention is not certain.

What other scientific instruments, and/or scientific subjects were affected by the ideas and/or inventions of Galileo?

Throughout the 17th century, different thermometers were developed, but the scales and accuracy of these instruments were questioned. In 1714, Gabriel Daniel Fahrenheit constructed a mercury thermometer which was the first to contain a reliable scale for measuring temperatures as low as the freezing/melting point of water (32F) and as high as the boiling point of water (212F). In 1742, the Swedish astronomer, Anders Celsius, proposed a new scale for thermometers. This "centesimal" (meaning 100 divisions) system was much easier to use for scientific work and became the basis for the "Celsius", or "Centigrade", temperature scale. When this scale was developed, Celsius classified the freezing/melting point of water as 100 degrees and the boiling point of water as 0 degrees. The inverse (0=freezing; 100=boiling) of this scale which we use today was introduced in 1743 by Jean Pierre Christin of Lyons. In 1862, Lord Kelvin, a Scottish mathematician and physicist, proposed an absolute temperature scale. Although many improvements to thermometers were yet to be made (and are still being made today), by the end of the 18th century satisfactory scientific investigations were being conducted about the temperature characteristics of our atmosphere.

Another product of 17th century investigations was the development of an instrument designed to measure atmospheric pressure - the barometer. The invention of the barometer is attributed to Evangelista Torricelli, an Italian mathematician who studied under Galileo. In 1643, Torricelli and a student, Vincenzo Viviani, constructed a vacuum tube and used mercury to measure the weight of the air.

As these meteorological instruments were being developed during the 18th and 19th centuries, other related technological developments impacted our knowledge of the atmosphere. The invention of the telegraph in 1843 allowed for the routine transmission of weather observations to and from observers stationed across the country. Using this data crude weather maps were drawn and surface wind patterns and storm systems could be identified and studied on much larger time and space scales.

If a weather map of the US could be drawn at this time (1843), how many states would it include? What would the map look like?

During the 1940's measurements of upper level meteorological variables became possible. Instruments used to measure temperature, humidity and pressure were placed on balloons and released into the atmosphere. Winds at upper levels were measured by tracking the balloons. These instrument systems (called radiosondes) allowed meteorologists to analyze the atmosphere in three dimensions and greatly improved our understanding of atmospheric processes.

The science took an additional leap forward in the 1950's with the development of high speed computers. Computer models were developed and the equations which approximated the physical processes of the atmosphere could be solved. These physical relationships are currently used to predict the future behavior of the atmosphere. The computers were also used to analyze and graphically represent the meteorological variables being measured at thousands of weather stations all over the Earth. In addition, RADAR was first used in the 1950's as an instrument to detect, from a distance (remotely), where precipitation was occurring.

On April 1, 1960, space age meteorology roared off the launch pad at Cape Canaveral as the first meteorological satellite was launched. This satellite, TIROS I, was the first of 50 satellites which have been successfully launched by the United States to provide day and night monitoring of world weather events. The data from these satellites have been instrumental in improving our knowledge of all weather systems (including fronts, thunderstorms, hurricanes, etc.). These satellites are now providing high speed computers with better data on the three dimensional structure of our atmosphere so that more accurate weather forecast methods can be developed. (see satellite resource guide for more information)

Student Activities: General meteorology history.