Meteorology
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Aristotle |
Meteorology is the scientific study of the
atmosphere that focuses on
weather processes and forecasting.
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. They are
temperature,
pressure,
water vapor, and the gradients and interactions of each variable, and how they change in time. The majority of Earth's observed weather is located in the
troposphere.
The applications of meteorology include
military meteorology which grew in importance during the 20th century.
Meteorology,
climatology,
atmospheric physics, and
atmospheric chemistry are sub-disciplines of the
atmospheric sciences. Meteorology and
hydrology comprise the interdiscplinary field of
hydrometeorology.
Early achievements in meteorology
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350 BCThe 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:
...all the affections we may call common to air and water, and the kinds and parts of the earth and the affections of its parts.
One of the most impressive achievements in
Meteorology is his description of what is now known as the
hydrologic cycle:
Now the sun, moving as it does, sets up processes of change and becoming and decay, and by its agency the finest and sweetest water is every day carried up and is dissolved into vapour and rises to the upper region, where it is condensed again by the cold and so returns to the earth.
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1607Galileo 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.
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1643Evangelista 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.
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1648Blaise Pascal discovers that
atmospheric pressure decreases with height, and deduces that there is a vacuum above the atmosphere.
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1667Robert Hooke builds an
anemometer to measure windspeed.
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1686Edmund Halley maps the trade winds, deduces that atmospheric changes are driven by solar heat, and confirms the discoveries of Pascal about atmospheric pressure.
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1735George 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.
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1743-1784Benjamin 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.
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1780Horace de Saussure constructs a hair
hygrometer to measure humidity.
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1802-1803Luke Howard writes
On the Modification of Clouds in which he assigns
cloud types Latin names.
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1806Francis Beaufort introduces his
system for classifying wind speeds.
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1837Samuel Morse invents the
telegraph.
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1838Controversial
Law of Storms work by William Reid
[http://www.magma.ca/~jdreid/reid.htm], 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.
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1841Elias Loomis the first person known to attempt to devise a theory on frontal zones.
[http://www.magma.ca/~jdreid/] This idea did not catch on until expanded upon by the Norwegians in the years following
World War I.
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1849Smithsonian begin to establish an observation network across the United States under the leadership of Joseph Henry.
[http://www.si.edu/archives/ihd/jhp/joseph03.htm]*
1860Robert 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
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A meteorologist at the console of the IBM 7090 in the Joint Numerical Weather Prediction Unit. c. 1965 |
In
1904 the Norwegian scientist
Vilhelm Bjerknes first postulated that prognostication of the weather is possible from calculation based upon
natural laws.
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.
Satellite observation
In
1960, the launch of
TIROS-1, the first successful
weather satellite marked the beginning of the age where weather information is available globally. Weather satellites along with more general-purpose Earth-observing satellites circling the earth at various altitudes have become an indispensable tool for studying a wide range of phenomena from forest fires to
El Niño.
In recent years,
climate models have been developed that feature a resolution comparable to older weather prediction models. These climate models are used to investigate long-term
climate shifts, such as what effects might be caused by human emission of
greenhouse gases.
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A meteorogist at work at the SPC in Norman, OK. |
Although meteorologists now rely heavily on computer models (numerical weather prediction), it is still relatively common to use techniques and conceptual models that were developed before computers were powerful enough to make predictions accurately or efficiently (generally speaking, prior to around 1980). Many of these methods are used to determine how much skill a forecaster has added to the forecast (for example, how much better than persistence or climatology did the forecast do?). Similarly, they could also be used to determine how much skill the industry as a whole has gained with emerging technologies and techniques.
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Persistence methodThe
persistence method assumes that conditions will not change. Often summarised as
"Tomorrow equals today". This method works best over short periods of time in stagnant weather regimes.
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Extrapolation methodThis assumes that the systems in the atmosphere propogate at similar speeds than seen in the past at some distance into the future. This method works best over short periods of time, and works best if you take diurnal changes in the pressure and precipitation patterns into account.
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Numerical forecasting methodThe
numerical weather prediction or
NWP method uses computers to take into account a large number of variables and creates a computer model of the atmosphere. This is most successful when used with the methods below, and when model biases and relative skill are taken into account. In general, the ECMWF model outperforms the NCEP ensemble mean, which outperforms the UKMET/GFS model after 72 hours, which outperform in the NAM model at most time frames. This performance changes when tropical cyclones are taken into account, as the ECMWF/model ensemble methods/model consensus/GFS/UKMET/NOGAPS/ all perform exceedingly well, with the NAM and Canadian GEM usually lagging behind.
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Consensus/ensemble methods of forecastingStatistically, it is difficult to beat the mean solution, and the consensus and ensemble methods of forecasting take advantage of the situation by only favoring models that have the greatest support with their ensemble means or other pieces of global model guidance. A local
Hydrometeorological Prediction Center study showed that using this method alone verifies 50-55% of the time.
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Trends methodThe
trends method involves determining the change in
fronts and high and low pressure centers in the model runs over various lengths of time. If the trend is seen over a long enough time frame (24 hours or so), it is more meaningful. The forecast models have been known to overtrend however, so use of this method verifies 55-60% the time, moreso in the surface pattern than aloft.
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Climatology/Analog methodThe
'climatology or analog method involves using historical weather data collected over long periods of time (years) to predict conditions on a given date. A variation on this theme is the use of teleconnections, which rely upon the date and the expected position of other positive or negative 500 hPa height anomalies to give someone an impression of what the overall pattern would look like with this anomaly in place, and is of more significant help than a model trend since it verifies roughly 75 percent of the time, when used properly and with a stable anomaly center. Another variation is the use of standard deviations from climatology in various meteorological fields. Once the pattern deviates more than 4-5 sigmas from climatology, it becomes an improbable solution.
With the development of powerful new
supercomputers like the
Earth Simulator in
Japan,
mathematical modeling of the atmosphere can reach unprecedented accuracy. This is not only due to the enhanced spatial and temporal resolution of the grids employed, but also because these more powerful machines can model the Earth as an integrated climate system, where atmosphere, ocean, vegetation, and man-made influences depend on each other realistically. The goal in global meteorological modeling can be termed
Earth System Modeling, with a growing number of models of various processes coupled to each other. Predictions for global effects like
Global Warming and
El Niño are expected to benefit substantially from these advancements.
Regional models are attracting more interest as the resolution of global models increases. With regional weather disasters such as the
Elbe flooding in
2002 and the
European heat wave in
2003, decision makers expect from these models accurate assessments about the possible increase of these natural hazards in a specific region. Countermeasures such as
dikes or intentional flooding might be effective in preventing or at least attenuating natural hazards.
For models at all scales, increased model resolution means less reliance on
parameterizations, which are empirically derived expressions for processes that cannot be resolved on the model grid. For example, in mesoscale models individual clouds can now be resolved, removing the need for formulations that average over a grid box. In global modeling,
atmospheric waves such as
gravity waves with short temporal and spatial scales can be represented without resorting to often overly simplified parameterizations.
Government
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Australian Bureau of Meteorology*
Chatham-Kent Meteorology Commission*
Meteorological Service of Canada*
Danish Meteorological Institute*
Direcção dos Serviços Meteorológicos e Geofísicos (Macau)
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Environment Canada Weather Office*
Hong Kong Observatory*
Indian Institute of Tropical Meteorology*
India Meteorological Department*
Japan Meteorological Agency*
Met Éireann (Ireland)
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Meteo Switzerland*
United Kingdom Meteorogical Office*United States:
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National Center for Atmospheric Research**
National Oceanic and Atmospheric Administration **
National Severe Storms Laboratory **
National Climatic Data Center**
National Weather Service ***
National Centers for Environmental Prediction ***
National Hurricane Center***
Storm Prediction Center*
Naval Maritime Forecast Center/
Joint Typhoon Warning Center*
Meteorological Service of New Zealand Limited*
Royal Meteorology Institute BelgiumMultinational
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European Centre for Medium-Range Weather Forecasts*
World Meteorological Organization**
Global Atmosphere WatchNGOs
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American Geophysical Union *
American Meteorological Society*
European Geosciences UnionEuropean Meteorological SocietyInternational Association of Broadcast MeteorologyNational Weather Association*
Royal Meteorological SocietyEducation
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Department of Marine, Earth, and Atmospheric Sciences at North Carolina State University*
Meteorological Institute Hamburg*
Atmospheric Science Program at UC Davis*
UCLA Atmospheric Science*
Department of Meteorology, University of Reading, UK*
University of Utah Department of Meteorology*
UIUC Department of Atmospheric Sciences*
Penn State University Department of Meteorology*
Wageningen University Meteorology Department, The Netherlands*
School of Meteorology, University of Oklahoma*
Meteorology at Millersville University*
University of Nebraska-Lincoln Meteorology Program*
Department of Atmospheric Science at Texas A&M University*
Wisconsin Atmospheric and Oceanic Sciences*
Washington Atmospheric Sciences*
San Francisco State Univ. Department of Geosciences*
San Jose State Univ. Department of Meteorology*
Univ. of Alaska Atmospheric SciencePlease see weather forecasting for actual weather forecast sites.*
Air Quality Meteorology - Online course that introduces the basic concepts of meteorology and air quality necessary to understand meteorological computer models. Written at a bachelor's degree level.
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The GLOBE Program - (Global Learning and Observations to Benefit the Environment) An international environmental science and education program that links students, teachers, and the scientific research community in an effort to learn more about the environment through student data collection and observation.
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Glossary of Meteorology - From the American Meteorological Society, an excellent reference of nomenclature, equations, and concepts for the more advanced reader.
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JetStream - An Online School for Weather - National Weather Service
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Learn About Meteorology - Australian Bureau of Meteorology
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Meteorology Education and Training (MetEd) - The COMET Program
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NOAA Central Library - National Oceanic & Atmospheric Administration
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Woother Weather Search - New Weather site with archives forecasts and forums.
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The World Weather 2010 Project The University of Illinois at Urbana-Champaign
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Uk weather dataSatellite imagery:
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Geostationary Satellite Imagery - NOAA National Environmental Satellite, Data, and Information Service
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Satellite Imagery - UK Met Office
