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In meteorology, an anticyclone is a weather phenomenon associated with atmospheric high pressure. 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. Meteorology is the scientific study of the atmosphere that focuses on weather processes and forecasting. ...
Composite satellite image showing the progress of a hurricane weather system approaching the east coast of America Weather comprises all the various phenomena that occur in the atmosphere of a planet. ...
A meteorological phenomenon is one of several commonplace or unusual weather events which illuminate and are explained by the principles of meteorology. ...
A high, or a high pressure area, is a region where the atmospheric pressure is greatest with relation to the surrounding area. ...
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 surface it may heat up locally, acquire water from the land or oceans or encounter warmer wet air. Local geography may cause a range of localised 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. In meteorology, an airmass or air mass is a large volume of air having fairly uniform characteristics of temperature, atmospheric pressure, and water vapor content. ...
Origin
An ingenious man who traveled widely and left his marks upon the world, Sir Francis Galton proposed the existence of the anticyclone. He wrote Meteorographica, or Methods of Mapping the Weather(1863). The discovery of the anticyclone enabled meteorologists to draw the modern weather map. Francis Galton Sir Francis Galton FRS (February 16, 1822 - January 17, 1911) was an English explorer, statistician, anthropologist, creator of modern eugenics (he coined the term), and investigator of the human mind. ...
Dry Air All anticyclones are produced by dry air that settles to the surface of the earth and accumulates, forming air masses. 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 vapor pressure is why. The two commomest parts of the air are Nitrogen (roughly 78% of the total) and Oxygen (roughly 21% of the total). 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. Displacement by vapor pressure produces intense tropical storms called hurricanes, typhoons, or baguios. The weight of air is called its air pressure. Boundaries: Phase, Pressure, Temperature 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 volume of Earths atmosphere, and is a useful value in aeronautics. ...
Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ...
The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor. ...
General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ...
General Name, Symbol, Number Oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16 (VIA), 2, p Density, Hardness 1. ...
Boundaries: Phase, Pressure, Temperature Evaporation/Sublimation Whenever a water molecule leaves a surface, it is said to have evaporated. ...
The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor. ...
General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ...
General Name, Symbol, Number Oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16 (VIA), 2, p Density, Hardness 1. ...
Displacement can have one of several meanings: Displacement (distance), a physical quantity in kinematics; Particle displacement, acoustics of sound in air. ...
The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor. ...
This article is about weather phenomena. ...
This article is about weather phenomena. ...
Atmospheric pressure is the pressure caused by the weight of air above any area in the Earths atmosphere. ...
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. 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. 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 far above the surface. The sea-level pressure may exceed 1040 millibars (hectopascals) (hPa) (SI). They tend to linger close to the place at which they had appeared. In meteorology, a cyclone is the rotation of a volume of air about an area of low atmospheric pressure. ...
Sea-level pressure or mean sea-level pressure (MSL or MSLP) is the standard that different weather stations employ to compare barometric pressure readings, which are made in inches of mercury. ...
A millibar (mb) is 1/1000th of a bar, a unit for measurement of pressure. ...
The pascal (symbol Pa) is the SI unit of pressure. ...
SI (disambiguation). ...
The Denmark Strait along the east coast of Greenland is a place where they appear, often, during the winter. They form part of the North Atlantic Oscillation that affects the weather much. The Beaufort Sea is an arm of the Arctic Ocean that exists north of northwestern Canada. An anticyclone called the Arctic High or the Beaufort High forms there. NSIDC (http://nsidc.org/arcticmet/patterns/anticyclones.html) The North Atlantic oscillation (NAO) is a complex climatic phenomenon in the North Atlantic Ocean (especially associated with fluctuations of climate between Iceland and the Azores). ...
Approximate area of the Beaufort Sea, and the disputed waters The Beaufort Sea is a large body of water north of The Northwest Territories, the Yukon, and Alaska and west of Canadas arctic islands that is a part of the Arctic Ocean. ...
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 Atlantic Ocean is Earths second-largest ocean, covering approximately one_fifth of its surface. ...
World map showing location of Europe A satellite composite image of Europe Europe is geologically and geographically a peninsula, forming the westernmost part of Eurasia. ...
Flag of Azores Shaded relief map of the Azores from 1975 The Azores ( Portuguese: Açores) are an archipelago of Portuguese islands in the middle of the Atlantic Ocean, about 1,500 km from Lisbon and about 3,900 km from the east coast of North America. ...
Since it has a tropical origin, its most proper name is extratropical anticyclone(but see the last paragraph, below). 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 ocean at a height of 3-4 miles (5-7km), the center of the high-pressure cell may be seen about 3,000 miles (5,000km) southwestwards of its surface position (which is in the general vicinity of the Azores Islands). The Atlantic Ocean is Earths second-largest ocean, covering approximately one_fifth of its surface. ...
Flag of Azores Shaded relief map of the Azores from 1975 The Azores ( Portuguese: Açores) are an archipelago of Portuguese islands in the middle of the Atlantic Ocean, about 1,500 km from Lisbon and about 3,900 km from the east coast of North America. ...
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. Sea-level pressure or mean sea-level pressure (MSL or MSLP) is the standard that different weather stations employ to compare barometric pressure readings, which are made in inches of mercury. ...
A millibar (mb) is 1/1000th of a bar, a unit for measurement of pressure. ...
The pascal (symbol Pa) is the SI unit 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 by thunderstorms. The Atlantic Ocean is Earths second-largest ocean, covering approximately one_fifth of its surface. ...
The Atlantic Ocean is Earths second-largest ocean, covering approximately one_fifth of its surface. ...
The ITCZ, or InterTropical Convergence Zone, is a belt of low pressure girdling the globe at the equator. ...
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 that used in the United states. Except for the wordage, there is no difference; there are no separate or different types of warm dry air anticyclones being generated by the ITCZ. Both extratropical cyclones and extratropical anticyclones are seen in the Northern Hemisphere, year-round. For an example of the Australian term, see: Equatorial trough (http://www.bom.gov.au/lam/glossary/epagegl.shtml) In meteorology, a cyclone is the rotation of a volume of air about an area of low atmospheric pressure. ...
External links Intertropical Convergence Zone photo (http://rsd.gsfc.nasa.gov/rsd/images/goes8_lg.jpg)
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