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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 thescience of meteorology. Those events are bound by the variables that exist in Earth 'satmosphere. They are temperature , pressure , water vapor , and the gradients and interactions ofeach variable, and how they change in time. The majority of Earth's observed weather is located in the troposphere .

Meteorology, climatology , atmospheric physics and atmosphericchemistry are sub-disciplines of the atmosphericsciences .

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2 Meteorology and climatology: somechallenges for this century

History of meteorology

Also refer to the timeline ofmeteorology

The term meteorology goes back to the book Meteorologica (about 340BC ) by Aristotle , who combined observations with speculation as to the originof celestial phenomena. The Greek word meteoron refers tothings "high in the sky", that is between Earth and the realm of the stars, whilelogos means "study". A similar work, called "Book of Signs", was published by Theophrastus , a pupil of Aristotle. It was centered more on predicting the weather by interpreting establishedcelestial phenomena, such as a halo aroundthe moon, without asking for explanations.

Further progress in the meteorological field had to wait until accurate instruments were available. Galileo constructed a thermometer in the 1500s , followed by Torricelli 's invention of the barometer in 1643 . The dependence of atmosphericpressure on height was first shown by Blaise Pascal and René Descartes . The anemometer for measuring wind speed was constructed in 1667 by Robert Hooke , while Horace de Saussure completedthis list of the most important meteorological instruments in 1780 with the hair hygrometer , which measures humidity .

Other advances that are usually thought of as part of the progression of physics were Robert Boyle 's investigation of the dependence of gas volume on pressure which lead to thermodynamics and Benjamin Franklin 's kite experiments with lightning .

The first essentially correct explanation of globalcirculation was the 1735 study by George Hadley of the Trade Winds , which gave rise tocalling the tropical cell of zonal mean atmospheric circulation the" Hadley cell ". In 1835 , Gaspard-Gustave Coriolis recognized that the rotation of Earth causes a velocity -dependent force on bodies in the reference frame of a nonrotating Earth.

Synoptic weather observations were still hindered by the difficulty ofestablishing certain weather characteristics such as clouds or wind . These were solved when Luke Howard and Francis Beaufort introduced theirsystems for classifying clouds ( 1803 ) and wind speeds ( 1806 ), respectively. The real turning point however was the invention of the telegraph in 1843 that allowed exchange of weather information withunprecedented speed.

Early in the 20th century , theoretical studies of atmospheric phenomenausually were performed analytically, that is by taking the fluid-dynamical equations that govern atmospheric flow, simplifyingthem by neglecting lesser terms, and looking for solutions to these equations. For example, Vilhelm Bjerknes developed the model that explains the generation, intensification and ultimatedecay (the life cycle ) of midlatitude cyclones , introducing the idea of fronts ,that is, sharply defined boundaries between air masses.

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 thelarge-scale movement of midlatitude Rossby waves , that is, the pattern of atmospheric lows and highs .

In the 1960s , the chaotic nature of theatmosphere was first understood by Edward Lorenz , founding the field of chaos theory . The mathematical advances achieved here later filtered backto meteorology and made it possible to describe the limits of predictability inherent in atmospheric modelling. This is known as the butterfly effect , because the growth of disturbances over time means that even one as minute as theflapping of a butterfly's wings could much later cause a large disturbance to form somewhere else.

In 1960 , the launch of TIROS-1 , the firstsuccessful weather satellite marked the beginning of the agewhere weather information is available globally. Weather satellites along with more general-purpose Earth-observing satellitescircling the earth at various altitudes have become an indispensable tool for studying a wide range of phenomena from forestfires to El Niño .

In recent years, climate models have been developed that feature aresolution 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 .

Meteorology and climatology: some challenges for this century

With the development of powerful new supercomputers like the Earth Simulator in Japan , numerical modeling of theatmosphere can reach unprecedented accuracy. This is not only due to the enhanced spatial and temporal resolution of the gridsemployed, 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 canthus currently be termed Earth System Modeling, with a growing number of models of various processes coupled to eachother. Predictions for global effects like Global Warming and El Niño are expected to benefit substantially from these advancements.

Regional models are also becoming more interesting as the resolution of global models increases and with the observed increasein 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 naturalhazards in specific regions and countermeasures (such as dikes or areas that are intentionally flooded to decrease the flooding somewhere else) that might beeffective in preventing or at least attenuating them.

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 themodel grid. For example, in mesoscale models individual clouds can now be resolved, removing the need for formulations thataverage over a grid box. In global modeling, atmospheric waves such as gravity waves with shorttemporal and spatial scales can be represented without resorting to often overly simplified parameterizations.

Possibilities for future improvements

With model output approaching observational data (e.g. from satellite soundings) in resolution, the sheer size of the datasetsmeans that data mining and data management will become equally important considerations in meteorological computing. In light ofthe decrease in density of surface and rawinsonde observations, new algorithmshave to be developed to extract similarly accurate information from satellite data, for example about cloud type anddistribution. Data management will become more global in nature, with some central archives storing a large number of numericalexperiments from various institutions. This data needs to have a sufficient amount of metadata attached and can then be conveniently retrieved by a WWW interfacefrom anywhere. These new archives will alleviate the important task of comparing experiments conducted with different models,which is instrumental for their further improvement. Also, gridcomputing may be an interesting way to harness the power of meteorological supercomputers more effectively. Of courseinternational cooperation is nothing unusual in modeling, but grid computing might automate the process of running a model wherethe right amount of computing resources are currently available and leave scientists more time for analyzing the results.

Meteorological instrumentation that is used at the surface or in airplanes alsohas room for improvement. Radar and lidar show precipitation and clouds by their effects on emitted monospectral electromagneticwaves . If radar measurements can be used to accurately determine the amount of precipitation (which as of now is onlypossible with rain gauges ), this would be beneficial for numericalweather prediction . Lidar can be used to study clouds that are so thin that they cannot be seen by the naked eye such ascertain types of cirrus filaments. Researchers continue to find new atmospheric detailssuch as high-altitude clouds that can form from contrails , which suggest that air travel may affect regional weather.

Aside from weather and climate prediction, weather modification has been (often covertly) attempted since the 1950s ---often by the military , but also at airports . But evenwithout consideration of anecdotal evidence of trying to use weather modification as a "weapon" (such as the supposed cloud seeding by US troops during the Vietnam conflict), it is clear that unilateral weather modificationmay lead to political tensions. Especially in the Middle East , thepossibility of wars about water supply looms for this century ( Hussein 's Iraq used surface engineering to block water from enteringthe land of the Marsh Arabs [1] ). While many of the proposed systemsfor modification of the water cycle belong more to the domain of engineering than to meteorology, it is clear that meteorology has taken on additionalpolitical dimensions such as the IPCC climate change mitigation proposals, and the UNFCCC pollution control limits with climate support payments from industrialized countries todeveloping countries.

Finally, meteorologists must educate the public more about weather and climate in general. Scientifically accurate andunderstandable information about topics like the ozone layer , climate change , the effects of deforestation , or sea level rise must bedisseminated and misinformation by special-interest groups be countered. Particularly in Europe, which may see an increase inextreme weather events as it already has in the 1990s , the population must be educated topay closer attention to severe weather warnings or information about other detrimental health factors such as high tropospheric ozone concentration or highlevels of UV radiation . Similarly, a better infrastructure to deal withnatural disasters must be developed akin to similar services in the US. Political decision makers should rely on scientificassessment and properly prepare for weather events and climate effects.

Meteorological topics and phenomena


Weather forecasting

Cyclone , anticyclone



Other Events

Weather-related disasters

Meteorological instrumentation and equipment

Institutions of meteorology/atmospheric science

See also: Timeline of meteorology , extreme value theory , Alfred Wegener .

Weather-related links

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