anticyclone

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anticyclone

anticyclone, region of high atmospheric pressure; anticyclones are commonly referred to as “highs.” The pressure gradient, or change between the core of the anticyclone and its surroundings, combined with the Coriolis effect, causes air to circulate about the core in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere. Near the surface of the earth the frictional drag of the surface on the moving air causes it to spiral outward gradually toward lower pressures while still maintaining the rotational direction. This outward movement of air is fed by descending currents near the center of the anticyclone that are warmed by compression as they encounter higher pressures at lower altitudes. The warming, in turn, greatly reduces the relative humidity, so that anticyclones, or “highs,” are generally characterized by few clouds and low humidity. Such weather characteristics may extend over an area from a few hundred to a few thousand miles wide. Many low-level anticyclones are swept generally eastward by the prevailing west-to-east flow of the upper atmosphere, usually traversing some 500 to 1,000 mi (800–1,600 km) per day. Other anticyclones are permanent or seasonal features of particular geographic regions. The term anticyclone is derived from the fact that the associated rotational direction and general weather characteristics of an anticylone are opposite to those of a cyclone.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Anticyclone

a region in the atmosphere characterized by increased atmospheric pressure. The pressure distribution in anticyclones is represented on charts by concentric closed isobars (lines of equal pressure) of an irregular, approximately oval shape. The highest pressure is at the center of the anticyclone; it decreases toward the periphery. The pressure at the center of an anticyclone at sea level reaches 1,025–1,040 millibars (mbar), and sometimes (for example, in Asia during the winter) as high as 1,070 mbars. (Average pressure at sea level is 1,010–1,015 mbar; 1,000 mbar ≈ 750 mmHg ≈ 1.02 kg force per sq cm.)

Along with cyclones, anticyclones are formed continuously in the troposphere (the lower part of the atmosphere). Both are part of the general atmospheric circulation, creating inter-latitudinal exchange of air masses. During the year many hundreds of anticyclones develop in each hemisphere. The duration of an anticyclone is several days; in some cases, even weeks. Both cyclones and anticyclones move in the direction of the general exchange of air in the troposphere—that is, from west to east—and in the process are deflected toward the lower latitudes. The average speed of movement of anticyclones is approximately 30 km/hr in the northern hemisphere and approximately 40 km/hr in the southern; however, anticyclones frequently remain almost stationary. In the northern hemisphere, the winds in an anticyclone move in a clockwise direction around the center, and in the southern hemisphere, in a counterclockwise direction, forming a gigantic whirlwind. The diameter of anticyclones is on the order of thousands of km.

Above the so-called friction layer—that is, above 1,000 m on the average—the wind in the anticyclone blows almost entirely along the lines of the isobars; however, in the friction layer the wind is deflected out from the isobars—at the earth’s surface, at an angle of approximately 30°. This flow of air from the anticyclone in the lower layer is accompanied by an influx of air into the anticyclone in the upper layers of the atmosphere and by its gradual settling and subsiding of the anticyclone. In subsiding, the air is heated adiabatically and becomes more unsaturated. Therefore the temperature of the troposphere in an anticyclone increases (only during the winter immediately above the land surface can the temperature be very low) and there is little overcast, and as a rule, no precipitation. The winds in the interior of the anticyclone are weak; however, they increase at the periphery.

As the degree of development and the temperature of the anticyclone increase, so does its height: the closed isobars appear in increasingly higher layers of the troposphere, and even in the lower stratosphere. The stratosphere in anticyclones begins at a higher altitude than in cyclones, and its temperature is lower.

S. P. KHROMOV

anticyclone

[‚an·tē′sī‚klōn]

(meteorology)

High-pressure atmospheric closed circulation whose relative direction of rotation is clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere, and undefined at the Equator. Also known as high-pressure area.

anticyclone

Wind flow direction in Northern Hemisphere.

Atmospheric circulations that rotate clock-wise in the Northern Hemisphere and anticlock-wise in the Southern Hemisphere. Anticyclones are areas of high pressure and are generally associated with light winds and good, stable weather. On weather charts, anticyclones are depicted by circular isobars with the high pressure at the center.

anticyclone

Meteorol a body of moving air of higher pressure than the surrounding air, in which the pressure decreases away from the centre. Winds circulate around the centre in a clockwise direction in the N hemisphere and anticlockwise in the S hemisphere

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

References in periodicals archive ?

When the anticyclone in the west of the South Asia high is enhanced, the zonal air flow along the periphery of the high is more likely to become northerlies; at the same time the anticyclone in the east of South Asia high becomes weak, and the IIBT is more intense and the trough turns out to be stronger.

A New Dynamical Index for India-Burma Trough

If the forecast of atmospheric pressure occurs under normal weather conditions, the predicted anticyclone over the observation station will occur in 4-5 days.

On the short-term prognosis of anticyclonic formations in vilnius by the hard cosmic ray flux variations/Trumpalaike anticiklonu formavimosi ties vilniumi prognoze pagal kietosios kosmines spinduliuotes srauto svyravimus

Briefly, stations with a SSH greater than 17 cm were considered to be within the core of the Loop Current or an associated eddy system and classified as "anticyclones" (warm core eddies) (Leben et al., 2002).

Distribution, growth, and mortality of sailfish (Istiophorus platypterus) larvae in the northern Gulf of Mexico

Paleoclimate, models have, for many years, postulated that a large glacial anticyclone existed in and around the retreating Laurentide ice sheet, particularly in summer.

Geological sciences

Figure 1 shows that during this period the AB is centered on average over 19oS and 21oS, showing comparatively more intense winds over the subtropics with a marked anticyclone curve (30oS-40oS).

Projected climate over the Central Andes countries caused by global warming

The Andes desiccate the west coast from 30[degrees] S north almost to the equator, undoubtedly amplifying the effects of the Humboldt Current and the eastern Pacific anticyclone.

Reconstruction of the biogeographical history of Malesherbiaceae

The strength of the southeast Pacific subtropical anticyclone is closely related to the anomalous Pacific tropical convection associated with ENSO (Aceituno 1988, Karoly 1989).

Fire history in northern Patagonia: the roles of humans and climatic variation

A third anticyclone, known as FA, that traveled along with BC and DE persists with no visible changes.

Images reveal stormy collision on Jupiter

The counterclockwise-moving storm, an anticyclone, boasts wind speeds (https://linkinghub.elsevier.com/retrieve/pii/S001910359895984X) as high as 300 miles per hour .

Jupiter's Great Red Spot: A 300-Year-Old Cyclone Persists But Is Shrinking

During this period, northeast China was under the influence of a persistent and extensive anticyclone centered around Lake Baikal (the Baikal high).

ATTRIBUTION OF THE PERSISTENT SPRING-SUMMER HOT AND DRY EXTREMES OVER NORTHEAST CHINA IN 2017: Anthropogenic climate change has increased the risk of 2017 northeast China persistent spring-summer hot and dry extremes by 5%-55% and 37%-113% respectively

Therefore if we are sitting under a high-pressure anticyclone, there can be very little, or no, wind.