Extratropical cycloneExtratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to severe gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth.
CyclogenesisCyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere (a low-pressure area). Cyclogenesis is an umbrella term for at least three different processes, all of which result in the development of some sort of cyclone, and at any size from the microscale to the synoptic scale. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, developing a warm core. Extratropical cyclones form as waves along weather fronts before occluding later in their life cycle as cold core cyclones.
Norwegian cyclone modelThe older of the models of extratropical cyclone development is known as the Norwegian cyclone model, developed during and shortly after World War I within the Bergen School of Meteorology. In this theory, cyclones develop as they move up and along a frontal boundary, eventually occluding and reaching a barotropically cold environment. It was developed completely from surface-based weather observations, including descriptions of clouds found near frontal boundaries.
Geostrophic windIn atmospheric science, geostrophic flow (ˌdʒiːəˈstrɒfɪk,ˌdʒiːoʊ-,-ˈstroʊ-) is the theoretical wind that would result from an exact balance between the Coriolis force and the pressure gradient force. This condition is called geostrophic equilibrium or geostrophic balance (also known as geostrophy). The geostrophic wind is directed parallel to isobars (lines of constant pressure at a given height). This balance seldom holds exactly in nature. The true wind almost always differs from the geostrophic wind due to other forces such as friction from the ground.
Geostrophic currentA geostrophic current is an oceanic current in which the pressure gradient force is balanced by the Coriolis effect. The direction of geostrophic flow is parallel to the isobars, with the high pressure to the right of the flow in the Northern Hemisphere, and the high pressure to the left in the Southern Hemisphere. This concept is familiar from weather maps, whose isobars show the direction of geostrophic winds. Geostrophic flow may be either barotropic or baroclinic.
Balanced flowIn atmospheric science, balanced flow is an idealisation of atmospheric motion. The idealisation consists in considering the behaviour of one isolated parcel of air having constant density, its motion on a horizontal plane subject to selected forces acting on it and, finally, steady-state conditions. Balanced flow is often an accurate approximation of the actual flow, and is useful in improving the qualitative understanding and interpretation of atmospheric motion.
Weather frontA weather front is a boundary separating air masses for which several characteristics differ, such as air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the boundary. For instance, cold fronts can bring bands of thunderstorms and cumulonimbus precipitation or be preceded by squall lines, while warm fronts are usually preceded by stratiform precipitation and fog. In summer, subtler humidity gradients known as dry lines can trigger severe weather.
GenevaGeneva (dʒəˈniːvə ; Genève ʒənɛv) is the second-most populous city in Switzerland (after Zürich) and the most populous city of Romandy, the French-speaking part of Switzerland. Situated in the south west of the country, where the Rhône exits Lake Geneva, it is the capital of the Republic and Canton of Geneva, and a center for international diplomacy. The city of Geneva (ville de Genève) had a population of 203,951 in 2020 (Jan. estimate) within its small municipal territory of , but the Canton of Geneva (the city and its closest Swiss suburbs and exurbs) had a population of 504,128 (Jan.
WindWind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet (Coriolis effect).
Atmosphere of VenusThe atmosphere of Venus is primarily of supercritical carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K (467 °C, 872 °F), and the pressure is , roughly the pressure found underwater on Earth. The Venusian atmosphere supports opaque clouds of sulfuric acid, making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging. Aside from carbon dioxide, the other main component is nitrogen.
Extraterrestrial atmosphereThe study of extraterrestrial atmospheres is an active field of research, both as an aspect of astronomy and to gain insight into Earth's atmosphere. In addition to Earth, many of the other astronomical objects in the Solar System have atmospheres. These include all the gas giants, as well as Mars, Venus and Titan. Several moons and other bodies also have atmospheres, as do comets and the Sun. There is evidence that extrasolar planets can have an atmosphere.
Geneva ConventionsThe Geneva Conventions are four treaties, and three additional protocols, that establish international legal standards for humanitarian treatment in war. The singular term Geneva Convention usually denotes the agreements of 1949, negotiated in the aftermath of the Second World War (1939–1945), which updated the terms of the two 1929 treaties and added two new conventions. The Geneva Conventions extensively define the basic rights of wartime prisoners, civilians and military personnel, established protections for the wounded and sick, and provided protections for the civilians in and around a war-zone.
Wind gradientIn common usage, wind gradient, more specifically wind speed gradient or wind velocity gradient, or alternatively shear wind, is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. It is the rate of increase of wind strength with unit increase in height above ground level. In metric units, it is often measured in units of meters per second of speed, per kilometer of height (m/s/km), which reduces to the standard unit of shear rate, inverse seconds (s−1).
Canton of GenevaThe Canton of Geneva, officially the Republic and Canton of Geneva, is one of the 26 cantons forming the Swiss Confederation. It is composed of forty-five municipalities, and the seat of the government and parliament is in the City of Geneva. Geneva is the French-speaking westernmost canton of Switzerland. It lies at the western end of Lake Geneva and on both sides of the Rhone, its main river. Within the country, the canton shares borders with Vaud to the east, the only adjacent canton.
Tropical cycloneA tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane (ˈhʌrᵻkən,_-keɪn), typhoon (taɪ'fuːn), tropical storm, cyclonic storm, tropical depression, or simply cyclone.
CycloneIn meteorology, a cyclone (ˈsaɪ.kloʊn) is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an anticyclone). Cyclones are characterized by inward-spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale (the synoptic scale).
AccelerationIn mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the orientation of the net force acting on that object. The magnitude of an object's acceleration, as described by Newton's Second Law, is the combined effect of two causes: the net balance of all external forces acting onto that object — magnitude is directly proportional to this net resulting force; that object's mass, depending on the materials out of which it is made — magnitude is inversely proportional to the object's mass.
Wind shearWind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal wind shear. Vertical wind shear is a change in wind speed or direction with a change in altitude. Horizontal wind shear is a change in wind speed with a change in lateral position for a given altitude.
Weather mapA weather map, also known as synoptic weather chart, displays various meteorological features across a particular area at a particular point in time and has various symbols which all have specific meanings. Such maps have been in use since the mid-19th century and are used for research and weather forecasting purposes. Maps using isotherms show temperature gradients, which can help locate weather fronts. Isotach maps, analyzing lines of equal wind speed, on a constant pressure surface of 300 or 250 hPa show where the jet stream is located.
Lake GenevaLake Geneva (le Léman lə lemɑ̃, lac Léman lak lemɑ̃, rarely lac de Genève lak də ʒ(ə)nɛv; Lago Lemano; Genfersee ˈɡɛnfərˌzeː; Lai da Genevra) is a deep lake on the north side of the Alps, shared between Switzerland and France. It is one of the largest lakes in Western Europe and the largest on the course of the Rhône. Sixty per cent () of the lake belongs to Switzerland (the cantons of Vaud, Geneva and Valais) and forty per cent () to France (the department of Haute-Savoie).
