The meteorology is the atmospheric study of the phenomena S such as the Nuage S, the depression S and the Précipitation S to include/understand how they are formed and evolved/moved. It is a discipline which treats mainly Mécanique fluids applied to the Air but which makes use of different other branches from the Physique and of the Chimie.

It thus makes it possible to establish weather forecasting while resting on mathematical model with runs like in the long run. It is also applied for the forecast of the Qualité of the air, for the climate changes and the study in several fields of human activity (construction, air traffic, etc)

History

Antiquity

  • 3000 av. J. - C.

Chinese Nei Tsing Sou Wen writes the first work on the meteorology which also includes/understands forecasts.

  • 400 av. J.C

In India, the periods of monsoon lead to the first measurements of quantity of precipitations fallen like to forecasts.

  • 350 av. J. - C.

The term meteorology comes from Aristote to describe what one would call the Sciences of the Earth in a general way and not the exclusive field of the study of the atmosphere. In particular, it describes the hydrous cycle as follows:

Maintaining the sun, moving like it does it, sets in motion a process of change, to become and of decline which by its action raises finest and soft water each day, dissolves it out of vapor and transports it towards the heights where it condenses again by the cold and turns over then to the ground.

  • 300 av. J. - C.

The Théophraste philosopher publishes “ the signs of time ”, first work of weather forecasting in Europe.

  • 1031-1095

Shen Kuo a well-read man having lived during the Dynasty of Song, in China, worked enter other things in meteorology. He wrote several descriptions of Tornade S and gave reason to a theory of Sun Sikong, explaining why the rainbows which are formed by the shade of the Sun under the rain, occur when the Sun is shining on him. Shen estimated that, although the trees were increasingly rare because of deforestation for the needs for the local industry of the Fer, “the Pétrole was produced continuously within the Earth” off publishes its discussed Law Storms which describes the behavior of the depression S. Its work divides the scientific community during ten years. Elias Loomis is the first to suggest the presence of face S to explain the weather but it is only after the First World War that the Norwegian school of meteorology will develop this concept. The Smithsonian Institution , under the direction of Joseph Henry start to set up a network of weather stations of observation at the the United States of America.

The November 14th, a violent storm causes the shipwreck of 41 French ships in Black Sea, during the Crimean War. This storm had crossed all Western Europe, but nobody was able to announce, to even prevent danger. Vis-a-vis this report, Urbain the Glassmaker, director of the Observatory of Paris, decides to set up a vast network of weather stations covering the whole of Europe and making profitable the technological innovation that recent the electric Télégraphe represents. This network gathers 24 stations including 13 connected by telegraph, then will extend to 59 observatories distributed on the unit from the Europe in 1865. Robert FitzRoy uses the telegraph for colliger the daily weather data coming from all the England and to trace the first charts synoptic S. By using the variation of these charts in time, it makes the first forecasts which it will start to publish in the newspaper The Times in 1860. It also develops a code by cones hoisted in the English ports to prevent arrival of Tempête S. The international weather Organization is founded with Vienna by the countries having a weather service. The principal promoter was American Matthew Fontaine Maury. After more than 200 lâchers of balloons, often carried out of night to avoid the effect of radiation of the sun, Leon Teisserenc de Bort discovered the tropopause in 1902. He concludes from it that the terrestrial atmosphere was composed of two layers, that he baptized Troposphère and Stratosphère, a convention which is always valid to date.

Contemporary era

The Norwegian meteorologists, under the direction of Vilhelm Bjerknes, develop the idea of the masses of air meeting along zones of discontinuity which one named the faces (hot Front, cold Front and Occlusion). According to this theory, there are three frontal zones between the four masses of air:

* Arctic

* Maritime
* Polar
* Tropical

By combining the force of Coriolis, these concepts and the compressive force, they explained the generation, the intensification and the decline of the weather systems of the average latitudes. The group included/understood Carl-Gustaf Rossby which was the first to explain atmospheric circulation with large scales in term of Mécanique of the fluids, Tor Bergeron which determined the mechanism of formation of the Pluie and Jacob Bjerknes.

This school of thought was spread universally. Still today, the simple weather explanations that one sees in the media use the vocabulary of the Norwegian school.

Meteorology in fact is connected to the mechanics of the fluids (see weather section science below). In 1922, Lewis Fry Richardson publishes Weather prediction by numerical process which describes how the minor terms of the equations of motion of the air can be neglected. This simplification makes it possible to solve them more easily. However it will be only with the arrival of the Ordinateur S that its idea will be really put in practice. The development of the Computer S at the end of the Second world war and during the years 1950 will lead to the formulation of programs Informatique S to solve the weather equations. It is the beginning of the numerical Prévision of time.

The weather Radar is developed starting from the studies made during the war on the echoes of noise caused by the Précipitation S:

*Aux the United States: development of the first operational weather radars thanks to several researchers, including inter alia David Atlas.

*Au Canada: J. Stewart Marshall and R.H. Douglas forms the “Stormy Weather Group” with the Université McGill of Montreal which worked on the relation between the Réflectivité (Z), the return of intensity of precipitation, and the rate of precipitation (R).
* In Great Britain, research relates on the characteristics of the owners of precipitations and to the possibilities that offer the various wavelengths between 1 and 10 centimetres.
The World Meteorological Organization (OMM) is founded by UNO to replace the international weather Organization.

In 1960, TIROS-1 is the first success of launching of a Meteorological satellite . This one marks the beginning of the weather data acquisition since space with a resolution of much higher than the ground stations in addition to probing places or not covered little before like the oceans, the deserts and the Pôles.

The Théorie of chaos will be applied to the atmosphere by Edward Lorenz during the years 1960. This concept will be developed later (as from the years 1990) in the systems of units which uses variations of the initial data in several master keys of digital models to see the variability of the results.

Then…

  • the development of the more powerful computers in the Years 1970 and of the Superordinateur S in the Années 1980 leads to a better resolution of the digital models.

  • research on the atmosphere, the Ocean S and their interrelationships, of phenomena such El Nino and the tropical cyclones leads to the improvement of knowledge of the weather phenomena and it follows from there better a Paramétrisation of the equations.

  • the study of the tendencies of temperatures and the concentrations of CO2 lead to the prediction of a total Réchauffement.

  • the instruments of data acquisition have largely advanced since 1960:

* Automation
* Improvement of the radars and the meteorological satellites as well as theirs resolution. This bringing of the direct surveys of the atmosphere.
* Development of the communications more universally to spread the forecasts as well as the weather alert .

Weather science

The goal of meteorology is to find the laws governing the Dynamique Fluide that one names the Air and to be able to predict its future behavior. The air is a compressible, formed fluid of different Gaz and being in a thin layer on the surface from a reference frame in rotation (the Ground). Meteorology being a branch of physics, the theory of the fluids, the calculation of the forces and thermodynamics are made profitable to explain the behavior of the atmosphere.

Behavior with large scales

See also: atmospheric primitive Equations, Cyclogénèse, Technical diagnostic of weather forecasting

Initially, to explain the movement of the air to the planetary scales, known as synoptic , one is ridged with seven unknown factors:

* Pressure (P)

* Temperature (T)
* Density of the air ( \, \ rho)
* Contained out of water (Q)
* Three dimensions X, there and Z

We thus need seven equations:

* the three Navier-Stokes equations of momentum connect the forces of pressure and Coriolis according to three dimensions;

* the Loi of perfect gases connects pressure and temperature;
* the hydrostatic equation connects the pressure and altitude:
\, \ delta P = - \ rho G \ delta z where G is the constant of gravity;
* the equation of mass continuity connects the variation of the mass in a volume of air and its form in time (see Navier-Stokes equations);
* the equation of composition connects the water contents of the air and its variation in space.

The equations of energy balance of the Thermodynamique take account of the phase shifts of one of the important components of the atmosphere: water.

To solve these equations is not easy because they comprise many terms which do not act all on the same scale. For example, in the equations of momentum, the equations calculate the movement of the air by the difference between the Gradient of pressure and the force of Coriolis. As the forces in question are almost equal, the difference will be of some orders of smaller magnitude. A miscalculation thus gives great differences in the result.

Moreover, the atmosphere is a system where the variables change value into each point. It is not possible to probe it with a resolution which would enable us to define his initial state perfectly. This is why, the first meteorologists initially developed empirical conceptual models to explain the behavior of the atmosphere. The faces, Hollow barometric S and other so well-known terms in the vocabulary of the presenters weather come from these first explanations of the time. They were made possible by the development of the means of survey of the atmosphere by the Aérologie.

Thereafter, the theories of the atmospheric dynamics and the data obtained the Radiosondage S made it possible to develop mathematical models by using only the most important terms in the equations and by simplifying the structure of the atmosphere. With the advent of data processing, the neglected terms could be gradually built-in although one did not manage yet to incorporate them all (see numerical Prévision of time).

However, meteorology is still handicapped by very the weak density of available data. The stations of survey are distant from several hundred kilometers from/to each other and even if remote sensors the such satellite and the radars increase the definition of the analysis, all this information comprises rather large inaccuracies. This is why, the forecast of time is still a mixture between calculations coming from the equations and the experiment of the meteorologist.

Behavior with small scales

See also: Storm, Tornado, Swirl of dust, Cyclone

The equations seen previously comprise certain assumptions which take for asset that the movements of the air and condensation occur rather slowly so that the pressure, the temperature and the contents out of water adapt gradually. However, when one goes down on smaller scales, about a few meters with a few kilometers, and when the movements are fast, certain of these equations are only approximations.

For example, the hydrostatic equilibrium equation is not respected in the storms where the water contained in the volumes of air in ascent, condenses more slowly than one could think it. Indeed, the variations of pressure and temperature occur not linearly in this case. The role of several researchers in meteorology is thus to inquire into the phenomena with small scales like the storms, the tornadoes and even into systems on broader scale, like the tropical cyclones, which comprise items on fine scale.

Specialities

Weather phenomena

Types of clouds

Direct and calculated data

Measuring devices and of observation

Indices

Weather technologies of control

There exists in the scientific literature no mechanism of modification deliberated on the time or the Climat which shows, theoretically or in practice, a capacity to assign time to large scales in a controlled way. Only some methods could, up to now, give located results, in favorable circumstances.

Here some examples of technologies aiming at obtaining some control on certain atmospheric conditions:

  • HAARP, technology of study and localized modification of the radioelectric properties of the Ionosphere;
  • Anti-hail gun: to try to disturb the formation of Hail by means of shock waves (anecdotic);
  • Sowing of the clouds: by releasing a money iodide smoke in the clouds to increase the number of cores of condensation available and thus the rain. This would in the case of have the storms for effect to increase the number of hail at the expense of their individual size;
  • Lamps fog to dissipate the fog by a warming localized.

Phenomena connected to the weather conditions

  • Anémomorphose : deformation of the form of the plants and the vegetable landscapes under the effect of the dominant winds and the spray.

  • Pile-up S caused by bad weather conditions
  • Turning into a desert had with the climate changes
  • Forest fires which had with the lightning or poked by the winds
  • the exposure to conditions of cold or heat extremes gives:
    • Hypothermie
    • Hyperthermie
  • Inondation S by abundant precipitations
  • the variations of atmospheric pressures is suspected of starting the Migraine S
  • the conditions of sunning and of heat are factors in the formation of the Ozone on the level of the ground and the Smog
  • Pluie of animals whose probable cause is the transport of animals by marine waterspouts
  • total Réchauffement which changes the climate.

Anecdote

An English law of 1677 condemned to roughing-hew the meteorologists, taxed with Sorcellerie. The law was repealed only in 1959. Fortunately, it was not always applied to the letter: Group Captain James Stagg, meteorologist as a chief, and the members of its three teams of forecast, predicted a lull for the unloading of Normandy the morning of the June 6th 1944, and did not have to undergo this fate.

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