Definitions

dynamic meteorology

Meteorology

[mee-tee-uh-rol-uh-jee]

'Meteorology(from Greek μετέωρος, metéōros, "high in the sky"; and -λογία, -logia) is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting (in contrast with climatology). 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.

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.

Sub-classifications

In the study of the atmosphere, meteorology can be divided into distinct areas of emphasis depending on the temporal scope and spatial scope of interest. 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 available based on the need by or by the unique, local or broad effects that are studied within that sub-class.Boundary layer meteorology Boundary layer meteorology is the study of processes in the air layer directly above Earth's surface, known as the atmospheric boundary layer (ABL) or peplosphere. The effects of the surface – heating, cooling, and friction – cause turbulent mixing within the air layer. Significant fluxes of heat, matter, or momentum on time scales of less than a day are advected by turbulent motions. Boundary layer meteorology includes the study of all types of surface-atmosphere boundary, including ocean, lake, urban land and non-urban land.Mesoscale meteorology Mesoscale meteorology is the study of atmospheric phenomena that has horizontal scales ranging from microscale limits to synoptic scale limits and a vertical scale that starts at the Earth's surface and includes the atmospheric boundary layer, troposphere, tropopause, and the lower section of the stratosphere. Mesoscale timescales last from less than a day to the lifetime of the event, which in some cases can be weeks. The events typically of interest are thunderstorms, squall lines, fronts, precipitation bands in tropical and extratropical cyclones, and topographically generated weather systems such as mountain waves and sea and land breezes.

Synoptic scale Synoptic scale meteorology is generally large area dynamics referred to in horizontal coordinates and with respect to time. The phenomena typically described by synoptic meteorology include events like extratropical cyclones, baroclinic troughs and ridges, frontal zones, and to some extent jets. All of these are typically given on weather maps for a specific time. The minimum horizontal scale of synoptic phenomena are limited to the spacing between surface observation stations.

Global scale Global scale meteorology is study of weather patterns related to the transport of heat from the tropics to the poles. Also, very large scale oscillations are of importance. Those oscillations have time periods typically longer than a full annual seasonal cycle, such as ENSO, PDO, MJO, etc. Global scale pushes the thresholds of the perception of meteorology into climatology. The traditional definition of climate is pushed in to larger timescales with the further understanding of how the global oscillations cause both climate and weather disturbances in the synoptic and mesoscale timescales.

Numerical Weather Prediction is a main focus in understanding air-sea interaction, tropical meteorology, atmospheric predictability, and tropospheric/stratospheric processes.. Currently (2007) Naval Research Laboratory in Monterey produces the atmospheric model called NOGAPS, a global scale atmospheric model, this model is run operationally at Fleet Numerical Meteorology and Oceanography Center. There are several other global atmospheric models.Dynamic meteorology Dynamic meteorology generally focuses on the physics of the atmosphere. The idea of air parcel is used to define the smallest element of the atmosphere, while ignoring the discrete molecular and chemical nature of the atmosphere. An air parcel is defined as a point in the fluid continuum of the atmosphere. The fundamental laws of fluid dynamics, thermodynamics, and motion are used to study the atmosphere. The physical quantities that characterize the state of the atmosphere are temperature, density, pressure, etc. These variables have unique values in the continuum.Aviation meteorology Aviation meteorology deals with the impact of weather on air traffic management. It is important for air crews to understand the implications of weather on their flight plan as well as their aircraft, as noted by the Aeronautical Information Manual:

The effects of ice on aircraft are cumulative-thrust is reduced, drag increases, lift lessens, and weight increases. The results are a decrease in stall speed and a deterioration of aircraft performance. In extreme cases, 2 to 3 inches of ice can form on the leading edge of the airfoil in less than 5 minutes. It takes but 1/2 inch of ice to reduce the lifting power of some aircraft by 50 percent and increases the frictional drag by an equal percentage.
Agricultural meteorology Meteorologists, soil scientists, agricultural hydrologists, and agronomists are persons concerned with studying the effects of weather and climate on plant distribution, crop yield, water-use efficiency, phenology of plant and animal development, and the energy balance of managed and natural ecosystems. Conversely, they are interested in the role of vegetation on climate and weather.Hydrometeorology Hydrometeorology is the branch of meteorology that deals with the hydrologic cycle, the water budget, and the rainfall statistics of storms. A hydrometeorologist prepares and issues forecasts of accumulating (quantitative) precipitation, heavy rain, heavy snow, and highlights areas with the potential for flash flooding. Typically the range of knowledge that is required overlaps with climatology, mesoscale and synoptic meteorology, and other geosciences.Nuclear meteorology Nuclear meteorology investigates the distribution of radioactive aerosols and gases in the atmosphere.

History

Ancient meteorology

In 350 BC, Aristotle wrote 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 described in the Meteorology is the description of what is now known as the hydrologic cycle:

The administration of the Mauryan Empire (322–185 BCE) categorized soils and made meteorological observations for use in Indian agriculture. In 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system.

In 80 AD, the Han Dynasty Chinese philosopher Wang Chong (27-97 AD), in Lun Heng (論衡; Critical Essays), dispels the myth of rain coming from the heavens, and states that rain is evaporated from water on the earth into the air and forms clouds, stating that clouds condense into rain and also form dew, and says when the clothes of people in high mountains are moistened, this is because of the air-suspended rain water. However, Wang Chong supports his theory by quoting a similar one of Gongyang Gao's, the latter's commentary on the Spring and Autumn Annals compiled in the 2nd century BC, showing that the Chinese conception of rain evaporating and rising to form clouds goes back much farther than Wang Chong. Wang Chong wrote:

Medieval meteorology

In the 9th century, Al-Kindi (Alkindus), an Arab naturalist, wrote a treatise on meteorology entitled Risala fi l-Illa al-Failali l-Madd wa l-Fazr (Treatise on the Efficient Cause of the Flow and Ebb), in which he presents an argument on tides which "depends on the changes which take place in bodies owing to the rise and fall of temperature." He is the first to employ an experimental method in the field, and he describes a clear and precise laboratory experiment in order to prove his argument. Also in the 9th century, Al-Dinawari, a Kurdish naturalist, writes 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, wells and other sources of water.

In the 10th century, Ibn Wahshiyya's Nabatean Agriculture discusses the weather forecasting of atmospheric changes and signs from the planetary astral alterations; signs of rain based on observation of the lunar phases, nature of thunder and lightning, direction of sunrise, behaviour of certain plants and animals, and weather forecasts based on the movement of winds; pollenized air and winds; and formation of winds and vapours. As weather forecasting predictions and the measurement of time and the onset of seasons became more precise and reliable, Muslim agriculturalists became informed of these advances and often employed them in agriculture, making it possible for them to plan the growth of each of their crops at specific times of the year.

In the early 11th century, Avicenna, a Persian scientist and polymath, invents the air thermometer. In 1021, Ibn al-Haytham (Alhazen), an Iraqi scientist, introduces the scientific method in his Book of Optics. He writes on the atmospheric refraction of light, for example, the cause of morning and evening twilight. He endeavored by use of hyperbola and geometric optics to chart and formulate basic laws on atmospheric refraction. He provides the first correct definition of the twilight, discusses atmospheric refraction, shows that the twilight is due to atmospheric refraction and only begins when the Sun is 19 degrees below the horizon, and uses a complex geometric demonstration to measure the height of the Earth's atmosphere as 52,000 passuum (49 miles), which is very close to the modern measurement of 50 miles. He also realized that the atmosphere also reflects light, from his observations of the sky brightening even before the Sun rises. Ibn al-Haytham later publishes his Risala fi l-Daw’ (Treatise on Light) as a supplement to his Book of Optics. He discusses the meteorology of the rainbow, the density of the atmosphere, and various celestial phenomena, including the eclipse, twilight and moonlight. In 1027, Avicenna publishes The Book of Healing, which contains his essay on mineralogy and meteorology in six chapters: formation of mountains; the advantages of mountains in the formation of clouds; sources of water; origin of earthquakes; formation of minerals; and the diversity of earth’s terrain. He also describes the structure of a meteor, and his theory on the formation of metals combined Geber's sulfur-mercury theory from Islamic alchemy (although he was critic of alchemy) with the mineralogical theories of Aristotle and Theophrastus. His scientific methodology of field observation was also original in Earth science.

In the late 11th century, Abu 'Abd Allah Muhammad ibn Ma'udh, who lived in Al-Andalus, wrote a work on optics later translated into Latin as Liber de crepisculis, which was mistakenly attributed to Alhazen. This was a short work containing an estimation of the angle of depression of the sun at the beginning of the morning twilight and at the end of the evening twilight, and an attempt to calculate on the basis of this and other data the height of the atmospheric moisture responsible for the refraction of the sun's rays. Through his experiments, he obtained the accurate value of 18°, which comes close to the modern value. In 1088, the Chinese scientist Shen Kuo, in his Dream Pool Essays (梦溪笔谈), wrote vivid descriptions of tornadoes, that rainbows were formed by the shadow of the sun in rain, occurring when the sun would shine upon it, and the curious common phenomena of the effect of lightning that, when striking a house, would merely scorch the walls a bit but completely melt to liquid all metal objects inside.

In 1121, Al-Khazini, a Muslim scientist of Byzantine Greek descent, publishes the The Book of the Balance of Wisdom, the first study on the hydrostatic balance. In the late 13th century and early 14th century, Qutb al-Din al-Shirazi and his student Kamāl al-Dīn al-Fārisī continued the work of Ibn al-Haytham, and they were the first to give the correct explanations for the rainbow phenomenon. In 1441, King Sejongs son, Prince Munjong, invented the first standardized rain gauge. 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 is known as the first anemometer. In 1494, Christopher Columbus experiences a tropical cyclone, leads to the first written European account of a hurricane.

Early modern meteorology

In 1607, Galileo Galilei constructs a thermoscope. In 1611, Johannes Kepler writes the first scientific treatise on snow crystals: "Strena Seu de Nive Sexangula (A New Year's Gift of Hexagonal Snow)". In 1620, Francis Bacon (philosopher) analyzes the scientific method in his philosophical work; Novum Organum. In 1643, Evangelista Torricelli invents the mercury barometer. In 1648, Blaise Pascal rediscovers that atmospheric pressure decreases with height, and deduces that there is a vacuum above the atmosphere.

In 1654, Ferdinando II de Medici establishes the first weather observing network, that consisted of meteorological stations in Florence, Cutigliano, Vallombrosa, Bologna, Parma, Milan, Innsbruck, Osnabruck, Paris and Warsaw. Collected data was centrally sent to Florence at regular time intervals. In 1662, Sir Christopher Wren invented the mechanical, self-emptying, tipping bucket rain gauge. In 1667, Robert Hooke builds another type of anemometer, called a pressure-plate anemometer. In 1686, Edmund Halley presents a systematic study of the trade winds and monsoons and identifies solar heating as the cause of atmospheric motions.

In 1714, Gabriel Fahrenheit creates reliable scale for measuring temperature with a mercury-type thermometer. In 1716, Edmund Halley suggests that aurorae are caused by "magnetic effluvia" moving along the Earth's magnetic field lines. In 1735, The first ideal explanation of global circulation was the study of the Trade winds by George Hadley. In 1738, Daniel Bernoulli publishes Hydrodynamics, initiating the kinetic theory of gases. He gave a poorly detailed equation of state, but also the basic laws for the theory of gases. In 1742, Anders Celsius, a Swedish astronomer, proposed the Celsius temperature scale which led to the current Celsius scale. In 1743, Benjamin Franklin is prevented from seeing a lunar eclipse by a hurricane, he decides that cyclones move in a contrary manner to the winds at their periphery.

In 1761, Joseph Black discovers that ice absorbs heat without changing its temperature when melting. In 1772, Black's student Daniel Rutherford discovers nitrogen, which he calls phlogisticated air, and together they explain the results in terms of the phlogiston theory. In 1777, Antoine Lavoisier discovers oxygen and develops an explanation for combustion. In 1783, in Lavoisier's book Reflexions sur le phlogistique, he deprecates the phlogiston theory and proposes a caloric theory. In 1783, the first hair hygrometer is demonstrated by Horace-Bénédict de Saussure.

In 1802-1803, Luke Howard writes On the Modification of Clouds in which he assigns cloud types Latin names. In 1804, Sir John Leslie observes that a matte black surface radiates heat more effectively than a polished surface, suggesting the importance of black body radiation. In 1806, Francis Beaufort introduces his system for classifying wind speeds. In 1808, John Dalton defends caloric theory in A New System of Chemistry and describes how it combines with matter, especially gases; he proposes that the heat capacity of gases varies inversely with atomic weight. In 1810, Sir John Leslie freezes water to ice artificially. In 1819, Pierre Louis Dulong and Alexis Thérèse Petit give the Dulong-Petit law for the specific heat capacity of a crystal.

In 1820, John Herapath develops some ideas in the kinetic theory of gases but mistakenly associates temperature with molecular momentum rather than kinetic energy; his work receives little attention other than from Joule. In 1822, Joseph Fourier formally introduces the use of dimensions for physical quantities in his Theorie Analytique de la Chaleur. In 1824, Sadi Carnot analyzes the efficiency of steam engines using caloric theory; he develops the notion of a reversible process and, in postulating that no such thing exists in nature, lays the foundation for the second law of thermodynamics. In 1827, Robert Brown discovers the Brownian motion of pollen and dye particles in water. In 1832, an electromagnetic telegraph was created by Baron Schilling. In 1834, Émile Clapeyron popularises Carnot's work through a graphical and analytic formulation. In 1835, Gaspard-Gustave Coriolis publishes theoretical discussions of machines with revolving parts and their efficiency, for example the efficiency of waterweels. At the end of the 19th century, meteorologists recognized that the way the Earth's rotation is taken into account in meteorology is analogous to what Coriolis discussed: an example of Coriolis Effect.

Observation networks and weather forecasting

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. 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 . Similar observation networks were established in Europe at this time. In 1854, the United Kingdom government appointed Robert FitzRoy to the new office of Meteorological Statist to the Board of Trade with the role of gathering weather observations at sea. FitzRoy's office became the United Kingdom Meteorological Office in 1854, the first national meteorological 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: Finnish Meteorological Central Office (1881) was formed from part of Magnetic Observatory of Helsinki University; India Meteorological Department (1889) established following tropical cyclone and monsoon related famines in the previous decades; United States Weather Bureau (1890) was established under the United States Department of Agriculture; Australian Bureau of Meteorology (1905) established by a Meteorology Act to unify existing state meteorological services.

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

In 1904, Norwegian scientist Vilhelm Bjerknes first postulated that prognostication of the weather is possible from calculations 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 without the use 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 mid-latitude 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 observed and 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 from the chaotic nature of the atmosphere.

Equipment

Generally speaking, each science has its own unique sets of laboratory equipment. However, meteorology is a science which does not use much lab equipment but relies more on field-mode observation equipment. In some aspects this can make simple observations slide on the erroneous side.

In science, an observation, or observable, is an abstract idea that can be measured and data can be taken. 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 ones to be 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.

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.

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.

The 1960 launch of the first successful weather satellite, TIROS-1, marked the beginning of the age where weather information became 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.

Weather forecasting

Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. Human beings have attempted to predict the weather informally for millennia, and formally since at least the nineteenth century. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve.

Once an all human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition, forecast models are now used to determine future conditions. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, teleconnections, knowledge of model performance, and knowledge of model biases. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference in current time and the time for which the forecast is being made (the range of the forecast) increases. The use of ensembles and model consensus help narrow the error and pick the most likely outcome.

There are a variety of end users to weather forecasts. Weather warnings are important forecasts because they are used to protect life and property. Forecasts based on temperature and precipitation are important to agriculture, and therefore to commodity traders within stock markets. Temperature forecasts are used by utility companies to estimate demand over coming days. On an everyday basis, people use weather forecasts to determine what to wear on a given day. Since outdoor activities are severely curtailed by heavy rain, snow and the wind chill, forecasts can be used to plan activities around these events, and to plan ahead and survive them.

See also

  • List of weather instruments
  • List of meteorology institutions
  • List of meteorology topics
  • Madden-Julian oscillation
  • Space weather
  • Walker circulation
  • References

    Further reading

    External links

    Please see weather forecasting for weather forecast sites.

    Satellite imagery:

    Base Reflectivity (Radar):

    Meteorology during Solar Eclipse

    Links to other keywords in meteorology Atmospheric conditions: Absolute stable air | Temperature inversion | Dine's compensation | precipitation | Cyclone | anticyclone | Thermal | Tropical cyclone (hurricane or typhoon) | Vertical draft | Extratropical cyclone

    Weather forecasting: atmospheric pressure | Low pressure area | High pressure area | dew point | weather front | jet stream | windchill | heat index | Theta-e | primitive equations | Pilot Reports

    Storm: thunderstorm | lightning | thunder | hail | tornado | convection | blizzard | supercell

    Climate: El Niño | monsoon | flood | drought | Global warming | Effect of sun angle on climate.

    Air Pollution: Air pollution dispersion modeling | Compilation of atmospheric dispersion models | Smog

    Other phenomena: deposition | dust devil | fog | tide | wind | cloud | air mass | evaporation | sublimation | ice | crepuscular rays | anticrepuscular rays

    Weather-related disasters: weather disasters | extreme weather

    Climatic or Atmospheric Patterns: Alberta clipper | El Niño | Derecho | Gulf Stream | La Niña | Jet stream | North Atlantic Oscillation | Madden-Julian oscillation | Pacific decadal oscillation | Pineapple Express | Sirocco | Siberian Express | Walker circulation

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