Meteorology



Meteorologists are scientists who study meteorology and are best known for forecasting the weather. Meteorologists work in government agencies, private consulting and research services, industrial enterprises, utilities, radio and television stations, and in education. In the United States, meteorologists held about 9,400 jobs in 2009. Many radio and television weather forecasters are professional meteorologists, while others are merely reporters (weather specialist, weatherman, etc.) with no formal meteorological training. The American Meteorological Society and National Weather Association issue "Seals of Approval" to weather broadcasters who meet certain requirements.




Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries. After the development of the computer in the latter half of the 20th century, breakthroughs in weather forecasting were achieved.

Meteorological phenomena are observable weather events which illuminate, and are explained by the science of meteorology. Those events are bound by the variables that exist in Earth's atmosphere; temperature, air pressure, water vapor, and the gradients and interactions of each variable, and how they change in time. Different spatial scales are studied to determine how systems on local, regional, and global levels impact weather and climatology.

Meteorology, climatology, atmospheric physics, and atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology. Interactions between Earth's atmosphere and the oceans are part of coupled ocean-atmosphere studies. Meteorology has application in many diverse fields such as the military, energy production, transport, agriculture and construction.




History of Meteorology

The beginnings of meteorology can be traced back to ancient India, as the Upanishads contain serious discussion about the processes of cloud formation and rain and the seasonal cycles caused by the movement of earth around the sun. Varahamihiras classical work Brihatsamhita, written about 500 AD, provides clear evidence that a deep knowledge of atmospheric processes existed even in those times.

350 BC - The term meteorology comes from Aristotle's Meteorology.

Although the term meteorology is used today to describe a subdiscipline of the atmospheric sciences, Aristotle's work is more general. The work touches upon much of what is known as the earth sciences. In his own words:

One of the most impressive achievements in Meteorology is his description of what is now known as the hydrologic cycle:

1607 - Galileo Galilei constructs a thermoscope. Not only did this device measure temperature, but it represented a paradigm shift. Up to this point, heat and cold were believed to be qualities of Aristotle's elements (fire, water, air, and earth).

Note: There is some controversy about who actually built this first thermoscope. There is some evidence for this device being independently built at several different times. This is the era of the first recorded meteorological observations. As there was no standard measurement, they were of little use until the work of Daniel Gabriel Fahrenheit and Anders Celsius in the 18th century.

1643 - Evangelista Torricelli, a contemporary and one-time assistant of Galileo, creates the first man-made sustained vacuum in 1643, and in the process creates the first barometer. Changes in height of mercury in this Toricelli Tube lead to his discovery that atmospheric pressure changes over time.

1648 - Blaise Pascal discovers that atmospheric pressure decreases with height, and deduces that there is a vacuum above the atmosphere.

1667 - Robert Hooke builds an anemometer to measure windspeed.

1686 - Edmund Halley maps the trade winds, deduces that atmospheric changes are driven by solar heat, and confirms the discoveries of Pascal about atmospheric pressure.

1735 - George Hadley is the first to take the rotation of the Earth into account to explain the behavior of the trade winds. Although the mechanism Hadley described was incorrect, predicting trade winds half as strong as the actual winds, the circulating cells that Hadley described later become known as Hadley cells.

1743-1784 - Benjamin Franklin observes that weather systems in North America move from west to east, demonstrates that lightning is electricity, publishes the first scientific chart of the Gulf Stream, links a volcanic eruption to weather, and speculates about the effect of deforestation on climate.

1780 - Horace de Saussure constructs a hair hygrometer to measure humidity.

1802-1803 - Luke Howard writes On the Modification of Clouds in which he assigns cloud types Latin names.

1806 - Francis Beaufort introduces his system for classifying wind speeds.

1837 - Samuel Morse invents the telegraph.

1838 - Controversial Law of Storms work by William Reid, which splits meteorological establishment into two camps in regard to low pressure systems. It would take over ten years of debate to finally come to a consensus on the behavior of low pressure systems.

1841 - Elias Loomis the first person known to attempt to devise a theory on frontal zones. This idea did not catch on until expanded upon by the Norwegians in the years following World War I.

1849 - Smithsonian begin to establish an observation network across the United States under the leadership of Joseph Henry.

1860 - Robert FitzRoy uses the new telegraph system to gather daily observations from across England and develops synoptic charts allowing predictions to be made, at the same time coining the term "weather forecast". The first ever daily weather forecasts were published by him in The Times in 1860, and in the following year a system was introduced of hoisting storm warning cones at principal ports when a gale was expected.

The Coriolis Effect - Understanding the kinematics of how exactly the rotation of the Earth affects airflow was partial at first. Late in the 19th century the full extent of the large scale interaction of pressure gradient force and deflecting force that in the end causes air masses to move along isobars was understood. Early in the 20th century this deflecting force was named the Coriolis effect after Gaspard-Gustave Coriolis, who had published in 1835 on the energy yield of machines with rotating parts, such as waterwheels.

In 1856, William Ferrel proposed the existence of a circulation cell in the mid-latitudes with air being deflected by the coriolis force to create the prevailing westerly winds.




Numerical Weather Prediction

Early in the 20th century, advances in the understanding of atmospheric physics led to the foundation of modern numerical weather prediction. In 1922, Lewis Fry Richardson published `Weather prediction by numerical process` which described how small terms in the fluid dynamics equations governing atmospheric flow could be neglected to allow numerical solutions to be found. However, the sheer number of calculations required was too large to be completed before the advent of computers.

At this time in Norway a group of meteorologists led by Vilhelm Bjerknes developed the model that explains the generation, intensification and ultimate decay (the life cycle) of midlatitude cyclones, introducing the idea of fronts, that is, sharply defined boundaries between air masses. The group included Carl-Gustaf Rossby (who was the first to explain the large scale atmospheric flow in terms of fluid dynamics), Tor Bergeron (who first determined the mechanism by which rain forms) and Jacob Bjerknes.

Starting in the 1950s, numerical experiments with computers became feasible. The first weather forecasts derived this way used barotropic (that means, single-vertical-level) models, and could successfully predict the large-scale movement of midlatitude Rossby waves, that is, the pattern of atmospheric lows and highs.In the 1960s, the chaotic nature of the atmosphere was first understood by Edward Lorenz, founding the field of chaos theory. These advances have led to the current use of ensemble forecasting in most major forecasting centers, to take into account uncertainty arising due to the chaotic nature of the atmosphere.




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