Meteorology

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This article is about the study of weather. For the science of measurement, see Metrology.
For the study of meteors, see Meteoritics. For other uses of the root word "meteor",
see Meteor (disambiguation).

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Meteorology is a branch of the atmospheric sciences which includes atmospheric

chemistry and atmospheric physics, with a major focus on weather forecasting. The study
of meteorology dates back millennia, though significant progress in meteorology did not
occur until the 18th century. The 19th century saw modest progress in the field
after weather observation networks were formed across broad regions. Prior attempts
at prediction of weather depended on historical data. It was not until after the elucidation of
the laws of physics and more particularly, the development of the computer, allowing for the
automated solution of a great many equations that model the weather, in the latter half of
the 20th century that significant breakthroughs in weather forecasting were achieved. An
important domain of weather forecasting is marine weather forecasting as it relates to
maritime and coastal safety, in which weather effects also include atmospheric interactions
with large bodies of water.
Meteorological phenomena are observable weather events that are explained by the
science of meteorology. Meteorological phenomena are described and quantified by the
variables of Earth's atmosphere: temperature, air pressure, water vapour, mass flow, and
the variations and interactions of those variables, and how they change over time.
Different spatial scales are used to describe and predict weather on local, regional, and
global levels.
Meteorology, climatology, atmospheric physics, and atmospheric chemistry are sub-
disciplines of the atmospheric sciences. Meteorology and hydrology compose the
interdisciplinary field of hydrometeorology. The interactions between Earth's atmosphere
and its oceans are part of a coupled ocean-atmosphere system. Meteorology has
application in many diverse fields such as the military, energy production,
transport, agriculture, and construction.
The word meteorology is from the Ancient Greek μετέωρος metéōros (meteor) and -λογία -
logia (-(o)logy), meaning "the study of things high in the air".

Contents

 1History

o 1.1Research of visual atmospheric phenomena

 o 1.2Instruments and classification scales

o 1.3Atmospheric composition research

o 1.4Research into cyclones and air flow

o 1.5Observation networks and weather forecasting

o 1.6Numerical weather prediction

 2Meteorologists

 3Equipment

 4Spatial scales

o 4.1Microscale

o 4.2Mesoscale

o 4.3Synoptic scale

o 4.4Global scale

 5Some meteorological principles

o 5.1Boundary layer meteorology

o 5.2Dynamic meteorology

 6Applications

o 6.1Weather forecasting

o 6.2Aviation meteorology

o 6.3Agricultural meteorology

o 6.4Hydrometeorology

o 6.5Nuclear meteorology

o 6.6Maritime meteorology

o 6.7Military meteorology

o 6.8Environmental meteorology

o 6.9Renewable energy

 7See also

 8References
 9Further reading

o 9.1Dictionaries and encyclopedias

 10External links

History[edit]
Main article: Timeline of meteorology

Parhelion (sundog) in Savoie

The ability to predict rains and floods based on annual cycles was evidently used by
humans at least from the time of agricultural settlement if not earlier. Early approaches to
predicting weather were based on astrology and were practiced by
priests. Cuneiform inscriptions on Babylonian tablets included associations between
thunder and rain. The Chaldeans differentiated the 22° and 46° halos.[1]
Ancient Indian Upanishads contain mentions of clouds and seasons.[2] The Samaveda
mentions sacrifices to be performed when certain phenomena were noticed.
[1]
Varāhamihira's classical work Brihatsamhita, written about 500 AD,[2] provides evidence of
weather observation.
In 350 BC, Aristotle wrote Meteorology.[3] Aristotle is considered the founder of meteorology.
[4]
One of the most impressive achievements described in the Meteorology is the description
of what is now known as the hydrologic cycle.[5]
The book De Mundo (composed before 250 BC or between 350 and 200 BC) noted[6]
If the flashing body is set on fire and rushes violently to the Earth it is called a
thunderbolt; if it is only half of fire, but violent also and massive, it is called
a meteor; if it is entirely free from fire, it is called a smoking bolt. They are all called
'swooping bolts' because they swoop down upon the Earth. Lightning is sometimes
smoky, and is then called 'smoldering lightning"; sometimes it darts quickly along,
and is then said to be vivid. At other times, it travels in crooked lines, and is
called forked lightning. When it swoops down upon some object it is called
'swooping lightning'.
The Greek scientist Theophrastus compiled a book on weather forecasting, called
the Book of Signs. The work of Theophrastus remained a dominant influence in the
study of weather and in weather forecasting for nearly 2,000 years. [7] In 25
AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic
zone system.[8] According to Toufic Fahd, around the 9th century, Al-Dinawari wrote
the Kitab al-Nabat (Book of Plants), in which he deals with the application of
meteorology to agriculture during the Muslim Agricultural Revolution. He describes the
meteorological character of the sky, the planets and constellations, the sun and moon,
the lunar phases indicating seasons and rain, the anwa (heavenly bodies of rain), and
atmospheric phenomena such as winds, thunder, lightning, snow, floods, valleys,
rivers, lakes.[9][10][verification needed]
Early attempts at predicting weather were often related to prophecy and divining, and
were sometimes based on astrological ideas. Admiral FitzRoy tried to separate
scientific approaches from prophetic ones.[11]
Research of visual atmospheric phenomena[edit]

Twilight at Baker Beach

See also: Rainbow and Twilight

Ptolemy wrote on the atmospheric refraction of light in the context of astronomical
observations.[12] In 1021, Alhazen showed that atmospheric refraction is also
responsible for twilight; he estimated that twilight begins when the sun is 19 degrees
below the horizon, and also used a geometric determination based on this to estimate
the maximum possible height of the Earth's atmosphere as 52,000 passim (about 49
miles, or 79 km).[13]
St. Albert the Great was the first to propose that each drop of falling rain had the form
of a small sphere, and that this form meant that the rainbow was produced by light
interacting with each raindrop.[14] Roger Bacon was the first to calculate the angular size
of the rainbow. He stated that a rainbow summit can not appear higher than 42 degrees
above the horizon.[15] In the late 13th century and early 14th century, Kamāl al-Dīn al-
Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the
primary rainbow phenomenon. Theoderic went further and also explained the
secondary rainbow.[16] In 1716, Edmund Halley suggested that aurorae are caused by
"magnetic effluvia" moving along the Earth's magnetic field lines.
Instruments and classification scales[edit]
See also: Beaufort scale, Celsius, and Fahrenheit

A hemispherical cup anemometer

In 1441, King Sejong's son, Prince Munjong of Korea, invented the first
standardized rain gauge.[17] These were sent throughout the Joseon
dynasty of Korea as an official tool to assess land taxes based upon a farmer's
potential harvest. In 1450, Leone Battista Alberti developed a swinging-
plate anemometer, and was known as the first anemometer.[18] In 1607, Galileo
Galilei constructed a thermoscope. In 1611, Johannes Kepler wrote the first scientific
treatise on snow crystals: "Strena Seu de Nive Sexangula (A New Year's Gift of
Hexagonal Snow)".[19] In 1643, Evangelista Torricelli invented the mercury barometer.
[18]
In 1662, Sir Christopher Wren invented the mechanical, self-emptying, tipping bucket
rain gauge. In 1714, Gabriel Fahrenheit created a reliable scale for measuring
temperature with a mercury-type thermometer.[20] In 1742, Anders Celsius, a Swedish
astronomer, proposed the "centigrade" temperature scale, the predecessor of the
current Celsius scale.[21] In 1783, the first hair hygrometer was demonstrated
by Horace-Bénédict de Saussure. In 1802–1803, Luke Howard wrote On the
Modification of Clouds, in which he assigns cloud types Latin names.[22] In 1806, Francis
Beaufort introduced his system for classifying wind speeds.[23] Near the end of the 19th
century the first cloud atlases were published, including the International Cloud Atlas,
which has remained in print ever since. The April 1960 launch of the first
successful weather satellite, TIROS-1, marked the beginning of the age where weather
information became available globally.
Atmospheric composition research[edit]
In 1648, Blaise Pascal rediscovered that atmospheric pressure decreases with height,
and deduced that there is a vacuum above the atmosphere.[24] In 1738, Daniel
Bernoulli published Hydrodynamics, initiating the Kinetic theory of gases and
established the basic laws for the theory of gases.[25] In 1761, Joseph Black discovered
that ice absorbs heat without changing its temperature when melting. In 1772, Black's
student Daniel Rutherford discovered nitrogen, which he called phlogisticated air, and
together they developed the phlogiston theory.[26] In 1777, Antoine
Lavoisier discovered oxygen and developed an explanation for combustion.[27] In 1783,
in Lavoisier's essay "Reflexions sur le phlogistique",[28] he deprecates the phlogiston
theory and proposes a caloric theory.[29][30] In 1804, Sir John Leslie observed that a
matte black surface radiates heat more effectively than a polished surface, suggesting
the importance of black-body radiation. In 1808, John Dalton defended caloric theory
in A New System of Chemistry and described how it combines with matter, especially
gases; he proposed that the heat capacity of gases varies inversely with atomic weight.
In 1824, Sadi Carnot analyzed the efficiency of steam engines using caloric theory; he
developed the notion of a reversible process and, in postulating that no such thing
exists in nature, laid the foundation for the second law of thermodynamics.
Research into cyclones and air flow[edit]
 General circulation of the Earth's atmosphere: The westerlies and trade winds are part of the
Earth's atmospheric circulation.

Main articles: Coriolis effect and Prevailing winds

In 1494, Christopher Columbus experienced a tropical cyclone, which led to the first
written European account of a hurricane.[31] In 1686, Edmund Halley presented a
systematic study of the trade winds and monsoons and identified solar heating as the
cause of atmospheric motions.[32] In 1735, an ideal explanation of global
circulation through study of the trade winds was written by George Hadley.[33] In 1743,
when Benjamin Franklin was prevented from seeing a lunar eclipse by a hurricane, he
decided that cyclones move in a contrary manner to the winds at their periphery.
[34]
Understanding the kinematics of how exactly the rotation of the Earth affects airflow
was partial at first. Gaspard-Gustave Coriolis published a paper in 1835 on the energy
yield of machines with rotating parts, such as waterwheels. [35] In 1856, William
Ferrel proposed the existence of a circulation cell in the mid-latitudes, and the air within
deflected by the Coriolis force resulting in the prevailing westerly winds. [36] Late in the
19th century, the motion of air masses along isobars was understood to be the result of
the large-scale interaction of the pressure gradient force and the deflecting force. By
1912, this deflecting force was named the Coriolis effect. [37] Just after World War I, a
group of meteorologists in Norway led by Vilhelm Bjerknes developed the Norwegian
cyclone model that explains the generation, intensification and ultimate decay (the life
cycle) of mid-latitude cyclones, and introduced the idea of fronts, that is, sharply
defined boundaries between air masses.[38] 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 how rain forms) and Jacob Bjerknes.
Observation networks and weather forecasting[edit]

Cloud classification by altitude of occurrence

This "Hyetographic or Rain Map of the World " was first published 1848 by Alexander Keith
Johnston.
 This "Hyetographic or Rain Map of Europe" was also published in 1848 as part of "The
Physical Atlas".

See also: History of surface weather analysis

In the late 16th century and first half of the 17th century a range of meteorological
instruments was invented – the thermometer, barometer, hydrometer, as well as wind
and rain gauges. In the 1650s natural philosophers started using these instruments to
systematically record weather observations. Scientific academies established weather
diaries and organised observational networks.[39] In 1654, Ferdinando II de
Medici established the first weather observing network, that consisted of meteorological
stations
in Florence, Cutigliano, Vallombrosa, Bologna, Parma, Milan, Innsbruck, Osnabrück,
Paris and Warsaw. The collected data were sent to Florence at regular time intervals.
[40]
In the 1660s Robert Hooke of the Royal Society of London sponsored networks of
weather observers. Hippocrates' treatise Airs, Waters, and Places had linked weather
to disease. Thus early meteorologists attempted to correlate weather patterns with
epidemic outbreaks, and the climate with public health.[39]
During the Age of Enlightenment meteorology tried to rationalise traditional weather
lore, including astrological meteorology. But there were also attempts to establish a
theoretical understanding of weather phenomena. Edmond Halley and George
Hadley tried to explain trade winds. They reasoned that the rising mass of heated
equator air is replaced by an inflow of cooler air from high latitudes. A flow of warm air
at high altitude from equator to poles in turn established an early picture of circulation.
Frustration with the lack of discipline among weather observers, and the poor quality of
the instruments, led the early modern nation states to organise large observation
networks. Thus by the end of the 18th century meteorologists had access to large
quantities of reliable weather data.[39] In 1832, an electromagnetic telegraph was
created by Baron Schilling.[41] The arrival of the electrical telegraph in 1837 afforded, for
the first time, a practical method for quickly gathering surface weather
observations from a wide area.[42]
This data could be used to produce maps of the state of the atmosphere for a region
near the Earth's surface and to study how these states evolved through time. To make
frequent weather forecasts based on these data required a reliable network of
observations, but it was not until 1849 that the Smithsonian Institution began to
establish an observation network across the United States under the leadership
of Joseph Henry.[43] Similar observation networks were established in Europe at this
time. The Reverend William Clement Ley was key in understanding of cirrus clouds
and early understandings of Jet Streams.[44] Charles Kenneth Mackinnon Douglas,
known as 'CKM' Douglas read Ley's papers after his death and carried on the early
study of weather systems.[45] Nineteenth century researchers in meteorology were
drawn from military or medical backgrounds, rather than trained as dedicated
scientists.[46] In 1854, the United Kingdom government appointed Robert FitzRoy to the
new office of Meteorological Statist to the Board of Trade with the task of gathering
weather observations at sea. FitzRoy's office became the United Kingdom
Meteorological Office in 1854, the second oldest national meteorological service in the
world (the Central Institution for Meteorology and Geodynamics (ZAMG) in Austria was
founded in 1851 and is the oldest weather service in the world). The first daily weather
forecasts made by FitzRoy's Office were published in The Times newspaper in 1860.
The following year a system was introduced of hoisting storm warning cones at
principal ports when a gale was expected.
Over the next 50 years many countries established national meteorological services.
The India Meteorological Department (1875) was established to follow tropical cyclone
and monsoon.[47] The Finnish Meteorological Central Office (1881) was formed from
part of Magnetic Observatory of Helsinki University.[48] Japan's Tokyo Meteorological
Observatory, the forerunner of the Japan Meteorological Agency, began constructing
surface weather maps in 1883.[49] The United States Weather Bureau (1890) was
established under the United States Department of Agriculture. The Australian Bureau
of Meteorology (1906) was established by a Meteorology Act to unify existing state
meteorological services.[50][51]
Numerical weather prediction[edit]
Main article: Numerical weather prediction

A meteorologist at the console of the IBM 7090 in the Joint Numerical Weather Prediction
Unit. c. 1965

In 1904, Norwegian scientist Vilhelm Bjerknes first argued in his paper Weather
Forecasting as a Problem in Mechanics and Physics that it should be possible to
forecast weather from calculations based upon natural laws.[52][53]
It was not until later in the 20th century that 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",
[54]
after finding notes and derivations he worked on as an ambulance driver in World
War I. He described how small terms in the prognostic fluid dynamics equations that
govern atmospheric flow could be neglected, and a numerical calculation scheme that
could be devised to allow predictions. Richardson envisioned a large auditorium of
thousands of people performing the calculations. However, the sheer number of
calculations required was too large to complete without electronic computers, and the
size of the grid and time steps used in the calculations led to unrealistic results. Though
numerical analysis later found that this was due to numerical instability.
Starting in the 1950s, numerical forecasts with computers became feasible.[55] The
first weather forecasts derived this way used barotropic (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.[56] In 1959, the UK Meteorological
Office received its first computer, a Ferranti Mercury.[57]
In the 1960s, the chaotic nature of the atmosphere was first observed and
mathematically described by Edward Lorenz, founding the field of chaos theory.
[58]
These advances have led to the current use of ensemble forecasting in most major
forecasting centers, to take into account uncertainty arising from the chaotic nature of
the atmosphere.[59] Mathematical models used to predict the long term weather of the
Earth (climate models), have been developed that have a resolution today that are as
coarse as the 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.

Meteorologists[edit]
Further information: Weather forecasting
Meteorologists are scientists who study meteorology.[60] The American Meteorological
Society published and continually updates an authoritative electronic Meteorology
Glossary.[61] 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. [62]
Meteorologists are best known by the public for weather forecasting. Some radio and
television weather forecasters are professional meteorologists, while others
are 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.

Equipment[edit]
 Satellite image of Hurricane Hugo with a polar low visible at the top of the image

Main article: Meteorological instrumentation

Each science has its own unique sets of laboratory equipment. In the atmosphere,
there are many things or qualities of the atmosphere that can be measured. Rain,
which can be observed, or seen anywhere and anytime was one of the first
atmospheric qualities measured historically. Also, two other accurately measured
qualities are wind and humidity. Neither of these can be seen but can be felt. The
devices to measure these three sprang up in the mid-15th century and were
respectively the rain gauge, the anemometer, and the hygrometer. Many attempts had
been made prior to the 15th century to construct adequate equipment to measure the
many atmospheric variables. Many were faulty in some way or were simply not reliable.
Even Aristotle noted this in some of his work as the difficulty to measure the air.
Sets of surface measurements are important data to meteorologists. They give a
snapshot of a variety of weather conditions at one single location and are usually at
a weather station, a ship or a weather buoy. The measurements taken at a weather
station can include any number of atmospheric observables. Usually,
temperature, pressure, wind measurements, and humidity are the variables that are
measured by a thermometer, barometer, anemometer, and hygrometer, respectively.
[63]
Professional stations may also include air quality sensors (carbon monoxide, carbon
dioxide, methane, ozone, dust, and smoke), ceilometer (cloud ceiling), falling
precipitation sensor, flood sensor, lightning sensor, microphone (explosions, sonic
booms, thunder), pyranometer/pyrheliometer/spectroradiometer (IR/Vis/UV photodiode
s), rain gauge/snow gauge, scintillation counter (background
radiation, fallout, radon), seismometer (earthquakes and
tremors), transmissometer (visibility), and a GPS clock for data logging. Upper air data
are of crucial importance for weather forecasting. The most widely used technique is
launches of radiosondes. Supplementing the radiosondes a network of aircraft
collection is organized by the World Meteorological Organization.
Remote sensing, as used in meteorology, is the concept of collecting data from remote
weather events and subsequently producing weather information. The common types
of remote sensing are Radar, Lidar, and satellites (or photogrammetry). Each collects
data about the atmosphere from a remote location and, usually, stores the data where
the instrument is located. Radar and Lidar are not passive because both use EM
radiation to illuminate a specific portion of the atmosphere.[64] 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.

Spatial scales[edit]
The study of the atmosphere can be divided into distinct areas that depend on both
time and spatial scales. At one extreme of this scale is climatology. In the timescales of
hours to days, meteorology separates into micro-, meso-, and synoptic scale
meteorology. Respectively, the geospatial size of each of these three scales relates
directly with the appropriate timescale.
Other subclassifications are used to describe the unique, local, or broad effects within
those subclasses.

Typical Scales of Atmospheric Motion Systems[65]

Type of motion Horizontal scale

 (meter)

Molecular mean free path 10−7

Minute turbulent eddies 10−2 – 10−1

Small eddies 10−1 – 1

Dust devils 1–10

Gusts 10 – 102

Tornadoes 102

Thunderclouds 103

Fronts, squall lines 104 – 105

Hurricanes 105

Synoptic Cyclones 106

Planetary waves 107

Atmospheric tides 107

Mean zonal wind 107