In meteorology, an anticyclone (that is, opposite to a cyclone) is a weather phenomenon in which there is a descending movement of the air and a high pressure area over the part of the planet's surface affected by it. Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary In Meteorology, a cyclone refers to an area of closed circular fluid motion rotating in the same direction as the Earth. The weather is a set of all the phenomena occurring in a given Atmosphere at a given Time. A meteorological phenomenon is a Weather event which can be explained by the principles of Meteorology. A high pressure area (also called a high or high-pressure is a region where the Atmospheric pressure is greater than surrounding areas A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is Anticyclonic flow spirals in a clockwise direction in the Northern Hemisphere and counter-clockwise in the Southern.
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Terminology
Confusion may be created by the fact that the term subtropical anticyclone is used by meteorologists in Australia in place of extratropical anticyclone, which is the term used in the United States. For a topic outline on this subject see List of basic Australia topics. The United States of America —commonly referred to as the Except for the wording, there is no difference; there are no separate or different types of warm dry air anticyclones being generated by the Intertropical Convergence Zone. The Intertropical Convergence Zone (ITCZ, also known as the Intertropical Front, Monsoon trough, Doldrums or the Equatorial Both extratropical cyclones and subtropical anticyclones are seen in the Northern Hemisphere, year-round. Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low For an example of the Australian term, see: Equatorial trough
Origin
The notable scientist Sir Francis Galton proposed the existence of the anticyclone as a part of his work in weather and writing Meteorographica, or Methods of Mapping the Weather (1863). Sir Francis Galton FRS ( 16 February 1822 &ndash 17 January 1911) half-cousin of Charles Darwin, was an The weather is a set of all the phenomena occurring in a given Atmosphere at a given Time. Galton's anticyclone hypothesis was eventually confirmed with the discovery of the anticyclone which enabled meteorologists to draw the modern weather map. Early versions of surface weather analysis charts produced prior to 1863 depicted cyclones, but not anticyclones. A surface weather analysis is a special type of Weather map that provides a view of Weather elements over a geographical area at a specified time based on information In Meteorology, a cyclone refers to an area of closed circular fluid motion rotating in the same direction as the Earth.
Formation
All anticyclones are produced by dry air that settles to the surface of the earth and accumulates, forming air masses. For airmass in Astronomy, see Airmass. In Meteorology, an air mass is a large volume of Air that The absence of aqueous vapor (water vapor) increases the density of air which means that each volumetric unit of dry air weighs more than the same volumetric unit of humid air at the same temperature and pressure. General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated The density of air, ρ (Greek rho (air density is the mass per unit volume of Earth's atmosphere, and is a useful value in Aeronautics. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The two most common parts of the air are nitrogen (roughly 78% of the total) and oxygen (roughly 21% of the total). Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Together, the two components weigh more than 99% of the total weight of the atmosphere. When air takes on aqueous vapor (water vapor), vapor pressure displaces some of the heavier nitrogen and oxygen, thus, a mixture that is lighter in weight overall is created. Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Displacement by vapor pressure produces intense tropical storms called hurricanes or typhoons. Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding
Anticyclogenesis
Cool or cold dry air type
Cool or cold dry air settles onto land and forms shallow anticyclones or high-pressure cells which often move across the terrain and create fair weather with little cloudiness or precipitation, then dissipate and vanish after reaching the open sea. Anticyclogenesis is the development or strengthening of anticyclonic circulation in the atmosphere A high pressure area (also called a high or high-pressure is a region where the Atmospheric pressure is greater than surrounding areas The types of anticyclones display different patterns of movement.
High-latitudes maritime type
In the months of winter, many strong cyclones appear at high latitudes. In Meteorology, a cyclone refers to an area of closed circular fluid motion rotating in the same direction as the Earth. Rising air in them eventually descends to form anticyclones. Tall anticyclones appear at some places each year during the coldest months. They may exceed 35,000 feet or 10,200 meters in height. The position of each anticyclone is at about the same place on the surface as it is the air far above the surface. The sea-level pressure may exceed 1040 millibars (hectopascals) (hPa) (SI). The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. They tend to linger close to the place at which they had appeared.
The Denmark Strait along the east coast of Greenland is a place where they often appear, particularly during the winter. The Denmark Strait (Danmarksstrædet Grænlandssund the latter meaning Greenland Strait is a Strait between Greenland (northwest and Iceland Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the They form part of the North Atlantic Oscillation that significantly influences the weather in that region of the Northern Hemisphere. The North Atlantic oscillation (NAO is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of Sea-level pressure between The Beaufort Sea is an arm of the Arctic Ocean that exists north of northwestern Canada. The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region is the smallest and shallowest of the world's five major Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page An anticyclone called the Arctic High or the Beaufort High forms there. NSIDC
Warm, dry air type
An anticyclone composed of warm dry air may be situated over much of the North Atlantic Ocean during most of the year. The warm dry air type of anticyclone is tall and may be observed on weather charts above three miles (5km) in height. The warm dry air type of anticyclone is usually described as being semipermanent. Frontal activity is not associated with it. Transoceanic in extent, in Europe it is called the Azores High, and in the United States it is known by the name Bermuda High. The Azores ( Açores ɐˈsoɾɨʃ or) is a Portuguese Archipelago in the Atlantic Ocean, about 1500 km (950 mi) from The United States of America —commonly referred to as the Ba (officially The Bermuda Islands or The Somers Isles) is a British overseas territory in the North Atlantic Ocean.
Since it has a tropical origin, its most proper name is extratropical anticyclone (but see "Terminology", above). It has a characteristic "vertical displacement" that shifts its center away from its surface position towards the equator and westwards, too. Far above the surface of the North Atlantic at a height of 3-4 miles (5-7km), the center of the high-pressure cell may be seen about 3,000 miles (5,000 km) southwestwards of its surface position (which is in the general vicinity of the Azores Islands). A high pressure area (also called a high or high-pressure is a region where the Atmospheric pressure is greater than surrounding areas The Azores ( Açores ɐˈsoɾɨʃ or) is a Portuguese Archipelago in the Atlantic Ocean, about 1500 km (950 mi) from
The maximum sea-level pressure in this type of anticyclone is not very high. It may reach, perhaps, 1025 millibars (hectopascals) or thereabouts during the summertime, which is a mere twelve millibars above the average sea-level pressure of 1013 millibars. The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure.
Similar anticyclones that are built of warm dry air exist over other oceanic areas of the world, such as the South Atlantic Ocean. The anticyclone that is located there is practically a mirror-image of the anticyclone that is located over the North Atlantic Ocean. Its vertical displacement is also towards the equator and westwards, too. The warm dry air is continually being produced in the Intertropical convergence zone (ITCZ) by thunderstorms. The Intertropical Convergence Zone (ITCZ, also known as the Intertropical Front, Monsoon trough, Doldrums or the Equatorial
Structure
At the surface the air tends to flow outwards in all directions from the central area of high pressure, and is deflected on account of the earth's rotation (see Coriolis effect) so as to give a spiral movement. In physics the Coriolis effect is an apparent deflection of moving objects when they are viewed from a Rotating frame of reference. In the northern hemisphere an anticyclone rotates in the clockwise direction, while it rotates counterclockwise in the southern hemisphere. The rotation is caused by the movement of colder higher pressure air that is moving away from the poles towards the equator being affected by the rotation of the earth. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the Since the air in an anticyclone is descending, it becomes warmed and dried, and therefore transmits radiation freely whether from the sun to the earth or from the earth into space.
Anticyclones generally bring fair weather and clear skies as the dynamics of an anticyclone lead to downward vertical movement which suppresses convective activity and generally lowers the mean relative humidity, in contrast to the upward vertical movement in a cyclone. However as the anticyclone moves over the earth's surface it may heat up locally, acquire water from the land or oceans or encounter warmer wet air.
Evolution
{link to Interactive Weather Satellite (NOAH GOES) and see the absence of water vapor in the global water vapor mosaic. }
Motion
Effects
In winter the anticyclonic weather is characterized by clear air with periods of frost, causing fogs in towns and low-lying damp areas, and in summer by still cloudless days with gentle variable winds and fine weather. The low, sharp inversion can lead to areas of persistent stratocumulus or stratus cloud, colloquially known as Anticyclonic gloom. In meteorology an inversion is a deviation from the normal change of an atmospheric property with altitude A stratocumulus Cloud belongs to a class characterized by large dark rounded masses usually in groups lines or waves the individual elements being larger than those in The type of weather brought about by an anticyclone depends on its origin. For example, extensions of the Azores high pressure may bring about anticyclonic gloom during the winter, as they are warmed at the base and will trap moisture as they move over the warmer oceans. High pressures that build to the north and extend southwards will often bring clear weather. This is due to being cooled at the base (as opposed to warmed) which helps prevent clouds from forming.
Local geography may cause a range of localized weather phenomena specific to anticyclones, while the interaction of the different air masses, which occurs at weather fronts, may cause a range of weather events. For airmass in Astronomy, see Airmass. In Meteorology, an air mass is a large volume of Air that A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena.
Extraterrestrial anticyclones
The Great Red Spot on Jupiter is an example of an extraterrestrial anticyclonic storm. Other storms include the recently formed Oval BA on Jupiter, Anne's Spot on Saturn, and the Great Dark Spot on Neptune.
References
- This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain. The Encyclopædia Britannica Eleventh Edition (1910–1911 is a 29-volume reference work that marked the beginning of the Encyclopædia Britannica The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone
See also
- Atmospheric circulation
- Atmospheric pressure
- Block (meteorology)
- Coriolis force
- Cyclone
- Earth's atmosphere
- Gyre
- High pressure area
- North American High
- Pressure system
- Siberian High
- Anticyclonic tornado
- Great Red Spot
External links
- Intertropical Convergence Zone photo - NASA Goddard Space Flight Center
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