The polar easterlies (also known as Polar Hadley cells) are the dry, cold prevailing winds that blow from the high-pressure areas of the polar highs at the North and South Poles towards the low-pressure areas within the westerlies at high latitudes. Like trade winds and unlike the westerlies, these prevailing winds blow from the east to the west, and are often weak and irregular. Due to the low sun angle, cold air builds up and subsides at the pole creating surface high-pressure areas, forcing an outflow of air toward the equator; that outflow is deflected westward by the Coriolis effect.
Polar easterlies
Prevailing winds
Prevailing winds | Polar easterlies
are the dry, cold prevailing winds that blow from the high-pressure areas towards the low-pressure areas. They  are the dry, cold prevailing winds that blow from the high-pressure areas of the polar highs at the North and South Poles towards the low-pressure areas within the westerlies at high latitudes. They are the dry, cold prevailing winds that blow from the high-pressure areas of the polar highs at the North and South Poles towards the low-pressure areas within the westerlies at high latitudes. They are the dry, cold prevailing winds that blow around the high-pressure areas of the polar highs at the North and South Poles.
what are the major global wind systems on earth
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polar easterlies, westerlies to name a few.
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what is the first one about?
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Easterly winds, on average, dominate the flow pattern across the poles, westerly winds blow across the mid-latitudes of the earth, polewards of the subtropical ridge, while easterlies again dominate the tropics. Directly under the subtropical ridge are the doldrums, or horse latitudes, where winds are lighter. Many of the Earth's deserts lie near the average latitude of the subtropical ridge, where descent reduces the relative humidity of the air mass. The strongest winds are in the mid-latitudes where cold polar air meets warm air from the tropics.
Wind | Global climatology
The polar easterlies (also known as Polar Hadley cells) are the dry, cold prevailing winds that blow from the high-pressure areas of the polar highs at the North and South Poles towards the low-pressure areas within the westerlies at high latitudes. Like trade winds and unlike the westerlies, these prevailing winds blow from the east to the west, and are often weak and irregular. Due to the low sun angle, cold air builds up and subsides at the pole creating surface high-pressure areas, forcing an outflow of air toward the equator; that outflow is deflected westward by the Coriolis effect.
Prevailing winds | Polar easterlies
The polar easterlies, also known as Polar Hadley cells, are dry, cold prevailing winds that blow from the high-pressure areas of the polar highs at the north and south poles towards the low-pressure areas within the Westerlies at high latitudes. Unlike the Westerlies, these prevailing winds blow from the east to the west, and are often weak and irregular. Because of the low sun angle, cold air builds up and subsides at the pole creating surface high-pressure areas, forcing an equatorward outflow of air; that outflow is deflected westward by the Coriolis effect.
Wind | Polar easterlies
The polar easterlies are the dry, cold prevailing winds that blow around the high-pressure areas of the polar highs at the North and South Poles. Cold air subsides at the poles creating high pressure zones, forcing an equatorward outflow of air; that outflow is then deflected westward by the Coriolis effect. Unlike the westerlies in the middle latitudes and trade winds in tropics, the polar easterlies are often weak and irregular. The polar easterlies are one of the five primary wind zones, known as wind belts, that make up our atmosphere's circulatory system. This particular belt of wind begins at approximately 60 degrees north and south latitude and reaches to the poles.
Polar easterlies | Introduction
The prevailing wind in a region of the Earth's surface is a surface wind that blows predominantly from a particular direction. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface. A region's prevailing and dominant winds are the result of global patterns of movement in the Earth's atmosphere. In general, winds are predominantly easterly at low latitudes globally. In the mid-latitudes, westerly winds are dominant, and their strength is largely determined by the polar cyclone. In areas where winds tend to be light, the sea breeze/land breeze cycle is the most important cause of the prevailing wind; in areas which have variable terrain, mountain and valley breezes dominate the wind pattern.
Prevailing winds | Introduction
The westerlies or the prevailing westerlies are the prevailing winds in the middle latitudes (i.e. between 35 and 65 degrees latitude), which blow in areas poleward of the high pressure area known as the subtropical ridge in the horse latitudes. These prevailing winds blow from the west to the east, and steer extra-tropical cyclones in this general direction. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. They are strongest in the winter when the pressure is lower over the poles, such as when the polar cyclone is strongest, and weakest during the summer when the polar cyclone is weakest and when pressures are higher over the poles.
Prevailing winds | Westerlies and their impact
The Westerlies or the Prevailing Westerlies are the prevailing winds in the middle latitudes between 35 and 65 degrees latitude. These prevailing winds blow from the west to the east, and steer extratropical cyclones in this general manner. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. They are strongest in the winter when the pressure is lower over the poles, and weakest during the summer and when pressures are higher over the poles. Together with the trade winds, the westerlies enabled a round-trip trade route for sailing ships crossing the Atlantic and Pacific Oceans, as the westerlies lead to the development of strong ocean currents on the western sides of oceans in both hemispheres through the process of western intensification.
Wind | Westerlies and their impact
The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region (between 30°N and 30°S latitudes). The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Trade winds have been used by captains of sailing ships to cross the world's oceans for centuries and enabled colonial expansion into the Americas and trade routes to become established across the Atlantic and Pacific oceans. In meteorology, they act as the steering flow for tropical storms that form over the Atlantic, Pacific, and southern Indian Oceans and make landfall in North America, Southeast Asia, and Madagascar and eastern Africa.
Trade winds | Introduction
These western ocean currents transport warm, sub-tropical water polewards toward the polar regions. The westerlies can be particularly strong, especially in the southern hemisphere, where there is less land in the middle latitudes to cause the flow pattern to amplify, which slows the winds down. The strongest westerly winds in the middle latitudes are within a band known as the Roaring Forties, between 40 and 50 degrees latitude south of the equator. The Westerlies play an important role in carrying the warm, equatorial waters and winds to the western coasts of continents, especially in the southern hemisphere because of its vast oceanic expanse.
Wind | Westerlies and their impact
Hot air rises at the Equator and is pushed towards the poles by cooler air travelling towards the Equator (an atmospheric circulation feature known as the Hadley Cell). At about 30 degrees from the equator, the outward-travelling air sinks to lower altitudes, and continues toward the poles closer to the ground (the Ferrel Cell), then rises up again from about 60 degrees as the air joins the Polar vortex. This travel in the 30 to 60 degree zone combines with the rotation of the earth to move the air currents from west to east, creating westerly winds. Unlike in the northern hemisphere, the large tracts of open ocean south of the 40th parallel south (interrupted only by Tasmania, New Zealand, and the southern part of South America) allow higher windspeeds to develop.
Roaring Forties | Mechanics
These occur when the westerly winds at 60N and 10 hPa reverse, i.e. become easterly. A complete disruption of the polar vortex is observed and the vortex will either be split into daughter vortices, or displaced from its normal location over the pole. According to the World Meteorological Organization's Commission for Atmospheric Sciences (Mclnturff, 1978): "a stratospheric warming can be said to be major if at 10 mb or below the latitudinal mean temperature increases poleward from 60 degree latitude and an associated circulation reversal is observed (that is, the prevailing mean westerly winds poleward of 60 latitude are succeeded by mean easterlies in the same area)."
Sudden stratospheric warming | Major
The winds have a strong influence on the waves and water circulation and through it the sea surface temperature. The wind follows a characteristic pattern, which shifts in latitude with the seasons and follows the Rossby waves as they move eastwards over the southern ocean. A southwesterly wind follows the passage of a cold front as the anticyclone moves east and merges with the South Atlantic High, producing strong south-easterly winds. The high pressure cell moves further over the tip of Africa and splits off the South Atlantic high, with weakening south easterly winds, followed by a coastal low with north-westerly wind before the next cold front, bringing cool, wet westerly wind which passes around Table Mountain and converges as a northerly wind over the bay.
False Bay | Winds
The net flow of water over the effective thickness of the current in these conditions is perpendicular to wind direction. Consistent prevailing winds set up persistent circulating surface currents in both hemispheres, and where the current is bounded by continental land masses, the resulting gyres are restricted in longitudinal extent. Seasonal and local winds cause smaller scale and generally transient currents, which dissipate after the driving winds die down. Real conditions often differ, as wind strength and direction vary, and the depth may not be sufficient for the full spiral to develop, so that the angle between wind direction and surface-water movement can be as small as 15°.
Wind generated current | Mechanism
Together with the trade winds, the westerlies enabled a round-trip trade route for sailing ships crossing the Atlantic and Pacific oceans, as the westerlies lead to the development of strong ocean currents in both hemispheres. The westerlies can be particularly strong, especially in the southern hemisphere, where there is less land in the middle latitudes to cause the flow pattern to amplify, which slows the winds down. The strongest westerly winds in the middle latitudes are called the Roaring Forties, between 40 and 50 degrees south latitude, within the Southern Hemisphere. The westerlies play an important role in carrying the warm, equatorial waters and winds to the western coasts of continents, especially in the southern hemisphere because of its vast oceanic expanse.
Prevailing winds | Westerlies and their impact
Wind occurs 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). Within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can dominate local winds.
Wind | Introduction
Polar winds are a driving force behind weather systems arising from three surface zones that converge at McMurdo Sound: the polar plateau and Transantarctic Mountains, the Ross Ice Shelf, and the Ross Sea. These surface zones create a range of dynamic weather systems. Cold, heavy air descending rapidly from the polar plateau at elevations of or more spawns fierce katabatic winds. These dry winds can reach hurricane force by the time they reach the Antarctic coast. Wind instruments recorded Antarctica's highest wind velocity at the coastal station Dumont d'Urville in July 1972 at (Australian Government Antarctica Division). Prevailing winds spilling into McMurdo Sound shoot between mountain passes and other land formations, stirring up blizzards known locally as "Herbies".
McMurdo Sound | Effects of wind
The wind is caused by differences in atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the lower pressure area, resulting in winds of various speeds. On a rotating planet, air will also be deflected by the Coriolis effect, except exactly on the equator. Globally, the two major driving factors of large-scale wind patterns (the atmospheric circulation) are the differential heating between the equator and the poles (difference in absorption of solar energy leading to buoyancy forces) and the rotation of the planet. Outside the tropics and aloft from frictional effects of the surface, the large-scale winds tend to approach geostrophic balance.
Wind | Causes
Due to the direction of the Earth's rotation, the prevailing wind in many places in the middle latitudes (i.e. between 35 and 65 degrees latitude) is from the west, known as the westerlies.
West | Weather
The data in "The Winds of the Globe" leads to conclusions that generally agree with those of its predecessor. Woeikof confirms the existence of the two Trade Winds found above 30° latitude, and established the existence of a third, southwesterly band between 0°-30° latitude. The greater wealth of data also allows Woeikof to give a more accurately describe the extent of these winds, each of the three spanning 30° latitude from the equator on top of the other. Another novel contribution was the realization that these wind bands shift with the seasons. When the sun is in its zenith over the northern hemisphere (our summer) the equatorial band moves northward, as do all the others.
James Henry Coffin | "Analysis"
In arid climates, the main source of erosion is wind. The general wind circulation moves small particulates such as dust across wide oceans thousands of kilometers downwind of their point of origin, which is known as deflation. Westerly winds in the mid-latitudes of the planet drive the movement of ocean currents from west to east across the world's oceans. Wind has a very important role in aiding plants and other immobile organisms in dispersal of seeds, spores, pollen, etc. Although wind is not the primary form of seed dispersal in plants, it provides dispersal for a large percentage of the biomass of land plants.
Wind | Role in the natural world
There are regular patterns of prevailing winds found in bands round the Earth's equatorial region. The zone designated the trade winds is the zone between about 30° N and 30° S, blowing predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The westerlies are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. The strongest westerly winds in the middle latitudes can come in the Roaring Forties between 30 and 50 degrees latitude.
Rain shadow | Regions of notable rain shadow
Prevailing winds can vary due to the uneven heating of the Earth.
Prevailing winds | Introduction
Air cooled by a glacier flows down the glacier and generates wind movement known as a "katabatic wind". In Antarctica, katabatic winds perpetually flow off the Antarctic plateau and are channelled through mountain passes, descending down steep glaciers to the oceans. They blow at storm force year round. The Strait of Magellan and the Aleutian Islands are prone to the existence of Williwaws, that is "a sudden violent, cold, katabatic gust of wind descending from a mountainous coast of high latitudes to the sea."
Katabasis | Wind
At an initial time a blocking-type circulation pattern establishes in the troposphere. This blocking pattern causes Rossby waves with zonal wavenumber 1 and/or 2 to grow to unusually large amplitudes. The growing wave propagates into the stratosphere and decelerates the westerly mean zonal winds. Thus the polar night jet weakens and simultaneously becomes distorted by the growing planetary waves. Because the wave amplitude increases with decreasing density this easterly acceleration process is not effective at fairly high levels. If the waves are sufficiently strong the mean zonal flow may decelerate sufficiently so that the winter westerlies turn easterly. At this point planetary waves may no longer penetrate into the stratosphere ).
Sudden stratospheric warming | Dynamics
Numerous articles have been published on and about the organization, the concept, and its personnel in the following publications. Some are in academic and professional publications: A.A. Bolonkin and R.B. Cathcart, "Antarctica: a southern hemisphere wind power station?", INT. J. GLOBAL ENVIRONMENTAL ISSUES 8: 262-273 (2008). [They propose windpower base of 450 GW output connected to the Global Energy Electric Grid via undersea HVDC cable.] Some are in general one:
Global Energy Network Institute | Selected Media References
The reverse happens in our winter. "The Winds of the Globe" also made significant progress towards empirically verifying the current theoretical association of the effect of air pressure on the direction of winds, as well as precisifying the previously poorly quantified relationship between pressure gradients and wind velocity. Contrarily, it served to problematize Hadley's contemporaneous theory about the movement of the upper atmosphere, and the effect of gravity on the shape of convection cells. Woeikof then applied these general conclusions to particular instances. Most notably, he was able to explain the mechanism behind the dry and wet seasons of Asia and Australia, as well as their corresponding monsoons.
James Henry Coffin | "Analysis"
Storms can last for days at a time.) These conditions continue through polar sunrise, but reverse dramatically with the onset of freshet, which brings high, gusting winds.
Dr. Neil Trivett Global Atmosphere Watch Observatory | Climate
The Ferrel cell is weak, because it has neither a strong source of heat nor a strong sink, so the airflow and temperatures within it are variable. For this reason, the mid-latitudes are sometimes known as the "zone of mixing." The Hadley and polar cells are truly closed loops, the Ferrel cell is not, and the telling point is in the Westerlies, which are more formally known as "the Prevailing Westerlies." The easterly Trade Winds and the polar easterlies have nothing over which to prevail, as their parent circulation cells are strong enough and face few obstacles either in the form of massive terrain features or high pressure zones.
Atmospheric circulation | Ferrel cell
If the Earth were tidally locked to the Sun, solar heating would cause winds across the mid-latitudes to blow in a poleward direction, away from the subtropical ridge. However, the Coriolis effect caused by the rotation of Earth tends to deflect poleward winds eastward from north (to the right) in the Northern Hemisphere and eastward from south (to the left) in the Southern Hemisphere. This is why winds across the Northern Hemisphere tend to blow from the southwest, but they tend to be from the northwest in the Southern Hemisphere. When pressures are lower over the poles, the strength of the westerlies increases, which has the effect of warming the mid-latitudes.
Westerlies | Behaviour
The trade winds (also called trades) are the prevailing pattern of easterly surface winds found in the tropics towards the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The trade winds act as the steering flow for tropical cyclones that form over the world's oceans. Trade winds also steer African dust westward across the Atlantic Ocean into the Caribbean, as well as portions of southeast North America. A monsoon is a seasonal prevailing wind that lasts for several months within tropical regions. The term was first used in English in India, Bangladesh, Pakistan, and neighboring countries to refer to the big seasonal winds blowing from the Indian Ocean and Arabian Sea in the southwest bringing heavy rainfall to the area.
Wind | Tropics
Katabatic winds are most commonly found blowing out from the large and elevated ice sheets of Antarctica and Greenland. The buildup of high density cold air over the ice sheets and the elevation of the ice sheets brings into play enormous gravitational energy. Where these winds are concentrated into restricted areas in the coastal valleys, the winds blow well over hurricane force, reaching around . In Greenland these winds are called piteraq and are most intense whenever a low pressure area approaches the coast. In a few regions of continental Antarctica the snow is scoured away by the force of the katabatic winds, leading to "dry valleys" (or "Antarctic oases") such as the McMurdo Dry Valleys.
Katabatic wind | Impacts
The westerlies are particularly strong, especially in the Southern Hemisphere, in areas where land is absent, because land amplifies the flow pattern, making the current more north-south oriented, slowing the westerlies. The strongest westerly winds in the middle latitudes can come in the roaring forties, between 40 and 50 degrees latitude. The westerlies play an important role in carrying the warm, equatorial waters and winds to the western coasts of continents, especially in the southern hemisphere because of its vast oceanic expanse.
Westerlies | Introduction
This trend reverses in the summer when strong heating of the land causes high pressure and tends to block moisture-rich air from the Pacific from reaching land. This explains why most of coastal North America in the highest latitude experiences dry summers, despite vast rainfall in the winter.
Prevailing winds | Westerlies and their impact
The pressure gradient, when combined with the Coriolis effect and friction, also influences wind direction. Rossby waves are strong winds in the upper troposphere. These operate on a global scale and move from West to East (hence being known as Westerlies). The Rossby waves are themselves a different wind speed from what we experience in the lower troposphere.
Wind speed | Factors affecting wind speed
The Virgin Islands lie in the “Easterlies” or “Trade Winds” which traverse the southern part of the "Bermuda High" pressure area. Thus, the predominant winds are usually from the east-northeast and east. These trade winds vary seasonally and are broadly divided into four seasonal modes: December to February; March to May; June to August; and September to November. There are numerous disturbances during the year, especially squalls and thunderstorms. These occur most frequently during the summer, lasting only a few hours and cause no pronounced change in the trade winds..
Hans Lollik Island | Trade winds
The Roaring Forties are strong westerly winds found in the Southern Hemisphere, generally between the latitudes of 40 and 50 degrees. The strong west-to-east air currents are caused by the combination of air being displaced from the Equator towards the South Pole, the Earth's rotation, and the scarcity of landmasses to serve as windbreaks. The Roaring Forties were a major aid to ships sailing the Brouwer Route from Europe to the East Indies or Australasia during the Age of Sail, and in modern usage are favoured by yachtsmen on round-the-world voyages and competitions. The boundaries of the Roaring Forties are not consistent, and shift north or south depending on the season.
Roaring Forties | Introduction
The trade winds (also called trades) are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator, equatorward of the subtropical ridge. These winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The trade winds act as the steering flow for tropical cyclones that form over world's oceans, guiding their path westward. Trade winds also steer African dust westward across the Atlantic Ocean into the Caribbean sea, as well as portions of southeast North America.
Prevailing winds | Trades and their impact
The thermal wind relation does not explain why the winds are organized into tight jets, rather than distributed more broadly over the hemisphere. One factor that contributes to the creation of a concentrated polar jet is the undercutting of sub-tropical air masses by the more dense polar air masses at the polar front. This causes surface low pressure and higher pressure at altitude. At high altitudes, lack of friction allows air to respond freely to the steep pressure gradient with low pressure at high altitude over the pole. This results in the formation of planetary wind circulations that experience a strong Coriolis deflection and thus can be considered 'quasi-geostrophic'.
Jet stream | Polar jet stream
The predominant wind direction is from the south-west.
Wedmore | Climate
The second theme of Held's research is the general circulation of the atmosphere. In one of his earliest papers, he showed that when a region is unstable to the large-scale planetary waves known as Rossby waves, the propagation of waves out of this region results in an easterly (westward) acceleration, which generates jet streams in midlatitudes. In contrast, regions in which these waves break experience an eastward (westerly) acceleration. Held also developed a theory for the Hadley circulation that would exist in the absence of atmospheric turbulence.
Isaac Held | Research
In 2012 there were 250 events around the globe and a very popular photo competition.
Global Wind Day | Introduction
The predominant wind direction is from the south-west.
Comeytrowe | Climate
The ancient Greek philosopher Aristotle, in his "Meteorology" (c. 340 BCE), introduced a ten-to-twelve wind system. One reading of his system is that there are eight principal winds: "Aparctias" (N), "Caecias" (NE), "Apeliotes" (E), "Eurus" (SE), "Notos" (S), "Lips" (SW), "Zephyrus" (W) and "Argestes" (NW). Aristotle then goes on to add two half-winds, "Thrascias" (NNW) and "Meses" (NNE), noting that they "have no contraries". Later, however, Aristotle suggests the "Phoenicias" wind for the SSE (blows locally in some places), but suggests nothing for SSW. So, seen this way, Aristotle really has an asymmetric windrose of ten winds, as two winds are effectively missing or only local.
Classical compass winds | Aristotle
Due to land masses in the northern hemisphere, largest temperature contrasts are observed on the east coast of North America (boundary between Canadian cold air mass and the Gulf Stream/warmer Atlantic) and Eurasia (boundary between the boreal winter monsoon/Siberian cold air mass and the warm Pacific). Therefore, the strongest boreal winter jet streams are observed over east coast of North America and Eurasia. Since stronger vertical shear promotes baroclinic instability, the most rapid development of extratropical cyclones (so called bombs) is also observed along the east coast of North America and Eurasia. The lack of land masses in the Southern Hemisphere leads to a more constant jet with longitude (i.e.
Thermal wind | Jet stream
Western boundary Eastern boundary Equatorial Arctic
Wind generated current | Oceanic wind driven currents
In meteorology, a williwaw is a sudden blast of wind descending from a mountainous coast to the sea. The word is of unknown origin, but was earliest used by British seamen in the 19th century. The usage appears for winds found in the Strait of Magellan, the Aleutian Islands and the coastal fjords of the Alaskan Panhandle, where the terms "outflow wind" and "squamish wind" are also used for the same phenomenon. On Greenland the word "piteraq" is used. The williwaw results from the descent of cold, dense air from coastal mountains in high latitudes. Thus the williwaw is considered a type of katabatic wind.
Williwaw | Introduction
As central pressures go, this was not particularly a powerful system; it was only 996 millibars the morning of the 17th. What contributed to the event, was the strong high pressure system (about 1040 millibars the morning of the 16th). It supplied the fresh cold air needed to change the precipitation over to sleet and freezing rain and increased the pressure gradient (and consequently the wind) between itself and the developing nor'easter low pressure system.
Global storm activity of 2007 | The metrological cause of the storm
The predominant wind direction is from the south-west.
Banwell | Climate
The "global terrestrial stilling" phenomenon is of great scientific, socioeconomic, and environmental interest because of the key impact of even small wind speed changes on atmospheric and ocean dynamics and related fields such as: (i) renewable wind energy; (ii) agriculture and hydrology due to evapotranspiration; (iii) migration of wind-dispersed plant species; (iv) wind-related natural disasters; (v) marine and coastal impacts due to wind-driven storm surges and waves; (vi) dispersion of air pollutants; among many other socioeconomic and environmental spheres. However, for wind energy near-surface wind speeds are mainly observed within 10m of the land surface, and with turbines being located some 60-80m above the land surface more studies are needed here.
Global terrestrial stilling | Implications of wind speed changes
As described earlier, prevailing and local winds are not spread evenly across the earth, which means that wind speeds also differ by region. In addition, the wind speed also increases with the altitude.
Wind | Average wind speeds
The predominant wind direction is from the south-west.
Westonzoyland | Climate
In regions with minimal vegetation, such as coastal and desert areas, transverse sand dunes orient themselves perpendicular to the prevailing wind direction, while longitudinal dunes orient themselves parallel to the prevailing winds.
Prevailing winds | Effect on nature
Western intensification applies to the western arm of an oceanic current, particularly a large gyre in such a basin. The trade winds blow westward in the tropics. The westerlies blow eastward at mid-latitudes. This applies a stress to the ocean surface with a curl in north and south hemispheres: causing Sverdrup transport equatorward (toward the tropics). Because of conservation of mass and potential vorticity conservation, that transport is balanced by a narrow, intense poleward current, which flows along the western coast, allowing the vorticity introduced by coastal friction to balance the vorticity input of the wind. The reverse effect applies to the polar gyres – the sign of the wind stress curl and the direction of the resulting currents are reversed.
Boundary current | Western intensification
The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend towards the poles and steer extratropical cyclones in this general manner. Tropical cyclones which cross the subtropical ridge axis into the westerlies recurve due to the increased westerly flow. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. The westerlies are strongest in the winter hemisphere and times when the pressure is lower over the poles, while they are weakest in the summer hemisphere and when pressures are higher over the poles.
Westerlies | Introduction
Loess, or windblown dust, can be employed as an indicator of past atmospheric circulation patterns. Without the presence of the monsoon, surface winds across the globe would have been primarily zonal and easterly. However, the geologic record not only indicates that winds exhibited a meridional, cross-equatorial pattern, but also that western Pangea experienced westerly flow during the peak period of the megamonsoon.
Pangean megamonsoon | Loess
Whereas it is true current global climate models fit these patterns as well, it is argued this is due to parametrization and not the veracity of the theories. This theory is in contradiction of the more traditional view that surface winds are solely a direct product of differences in surface heating and heat released from condensation. The creators of the theory argue that phase changes in water play a greater role in atmospheric dynamics than currently acknowledged. Publication of the paper was preceded by an extended editorial debate at the publishing journal, based on highly critical peer reviews.
Biotic pump | Introduction
A katabatic wind originates from radiational cooling of air atop a plateau, a mountain, glacier, or even a hill. Since the density of air is inversely proportional to temperature, the air will flow downwards, warming approximately adiabatically as it descends. The temperature of the air depends on the temperature in the source region and the amount of descent. In the case of the Santa Ana, for example, the wind can (but does not always) become hot by the time it reaches sea level. In Antarctica, by contrast, the wind is still intensely cold. The entire near-surface wind field over Antarctica is largely determined by the katabatic winds, particularly outside the summer season, except in coastal regions when storms may impose their own wind field.
Katabatic wind | Theory
The predominant wind direction is from the south-west.
Burnham-on-Sea | Climate
Enhanced surface (upper level) westerly winds occur near the west (east) side of the active convection. Ocean currents, up to in depth from the ocean surface, follow in phase with the east-wind component of the surface winds. In advance, or to the east, of the MJO enhanced activity, winds aloft are westerly. In its wake, or to the west of the enhanced rainfall area, winds aloft are easterly. These wind changes aloft are due to the divergence present over the active thunderstorms during the enhanced phase. Its direct influence can be tracked poleward as far as 30 degrees latitude from the equator in both northern and southern hemispheres, propagating outward from its origin near the equator at around 1 degree latitude, or , per day.
Madden–Julian oscillation | Behavior
The wind belts girdling the planet are organised into three cells in each hemisphere—the Hadley cell, the Ferrel cell, and the polar cell. Those cells exist in both the northern and southern hemispheres. The vast bulk of the atmospheric motion occurs in the Hadley cell. The high pressure systems acting on the Earth's surface are balanced by the low pressure systems elsewhere. As a result, there is a balance of forces acting on the Earth's surface. The horse latitudes are an area of high pressure at about 30° to 35° latitude (north or south) where winds diverge into the adjacent zones of Hadley or Ferrel cells, and which typically have light winds, sunny skies, and little precipitation.
Atmospheric circulation | Latitudinal circulation features
The formation of AAIW can be explained very simply through the Ekman transport process and the divergence and convergence of water masses. The winds over Antarctica are called the polar easterlies where winds blow from the east to the west. This creates a counter-clockwise surface current near the coast of Antarctica, called the Antarctic Coastal Current. Ekman transport causes the water to push towards the left of the surface motion in the Southern Hemisphere. Thus, this westward directed coastal current in Antarctica will push the water towards Antarctica. At the same time there is a strong current north of the Antarctic Coastal Current, called the Antarctic Circumpolar Current (ACC) created by the strong westerlies in this region which flows clockwise around Antarctica.
Antarctic Intermediate Water | Formation
Low-pressure weather systems with inward winds (such as a hurricane) spin counterclockwise north of the equator, but clockwise south of the equator. This is due to the Coriolis force, and requires that (assuming they are attached to each other and rotating in the same direction) the north and southern halves of the Earth are angled in opposite directions (e.g. the north is facing toward Polaris and the south is facing away from it).
Spherical Earth | Weather systems
The predominant wind direction is from the south-west.
Glastonbury | Climate
The worldwide solar-driven wind results in the so-called Sq (solar quiet) current system in the E region of the Earth's ionosphere (ionospheric dynamo region) ( altitude). Resulting from this current is an electrostatic field directed west–east (dawn–dusk) in the equatorial day side of the ionosphere. At the magnetic dip equator, where the geomagnetic field is horizontal, this electric field results in an enhanced eastward current flow within ± 3 degrees of the magnetic equator, known as the equatorial electrojet.
Ionosphere | Equatorial electrojet
The poleward movement of the air in the upper part of the troposphere deviates toward the east, caused by the coriolis acceleration (a manifestation of conservation of angular momentum). At the ground level, however, the movement of the air toward the equator in the lower troposphere deviates toward the west, producing a wind from the east. The winds that flow to the west (from the east, easterly wind) at the ground level in the Hadley cell are called the Trade Winds. Though the Hadley cell is described as located at the equator, in the northern hemisphere it shifts to higher latitudes in June and July and toward lower latitudes in December and January, which is the result of the Sun's heating of the surface.
Atmospheric circulation | Hadley cell
Then the northern air will expand in a southerly direction because of the heat due to the contraction of the southern air. Therefore most of the summer winds are merits and most of the winter winds are not.
Al-Kindi | Meteorology
The quasi-biennial oscillation (QBO), is a quasiperiodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. The alternating wind regimes develop at the top of the lower stratosphere and propagate downwards at about per month until they are dissipated at the tropical tropopause. Downward motion of the easterlies is usually more irregular than that of the westerlies. The amplitude of the easterly phase is about twice as strong as that of the westerly phase. At the top of the vertical QBO domain, easterlies dominate, while at the bottom, westerlies are more likely to be found.
Quasi-biennial oscillation | Introduction
In 1494, Christopher Columbus experienced a tropical cyclone, which led to the first written European account of a hurricane. In 1686, Edmund Halley presented a systematic study of the trade winds and monsoons and identified solar heating as the cause of atmospheric motions. In 1735, an "ideal" explanation of global circulation through study of the trade winds was written by George Hadley. In 1743, when Benjamin Franklin was prevented from seeing a lunar eclipse by a hurricane, he decided that cyclones move in a contrary manner to the winds at their periphery. Understanding the kinematics of how exactly the rotation of the Earth affects airflow was partial at first.
Meteorology | Research into cyclones and air flow
By manipulating the outflow and direction of theses fans the facility will be capable of producing time-dependent, straight, sheared or swirl winds of variable directionality. Therefore, a large variety of wind fields such as boundary layers, portions of hurricanes, tornados, downbursts, low level currents or gust fronts will be physically simulated. An active topographic capability will generate a wide diversity of surface topographies at unprecedented scales allowing wind simulations over areas of the order of 10 km2 . The same system will be used to locally seed for the Particle Image Velocimetry (PIV) system that will measure the wind field over extended areas.
WindEEE Dome | WindEEE Dome
If more energy goes out, the energy budget is negative and Earth experiences cooling. More energy reaches the tropics than the polar regions and the subsequent temperature difference drives the global circulation of the atmosphere and oceans. Air rises when it warms, flows polewards and sinks again when it cools, returning to the equator. Due to the conservation of angular momentum, the Earth's rotation diverts the air to the right in the Northern Hemisphere and to the left in the Southern hemisphere, thus forming distinct atmospheric cells. Monsoons, seasonal changes in wind and precipitation that occur mostly in the tropics, form due to the fact that land masses heat up more easily than the ocean.
Climate system | Energy and general circulation
The "global terrestrial stilling" is not affecting in the same way the whole Earth's surface across both land and ocean surfaces. Spatially, increasing wind speed trends have been reported for some regions, in particular for high-latitudes, coastal and for ocean surfaces where different authors have evidenced an increased global trend of wind speed using satellite measurements in the last 30–40 years. Recent studies have shown a break in the negative tendency of terrestrial wind speeds, with a recent widespread recovery / strengthening of wind speed since around 2013. This creates uncertainty in understanding the phenomenon. Most of the uncertainties behind the "global terrestrial stilling" debate resides in (i) the short wind speed data availability, with series starting in the 1960s, (ii) wind speed studies mainly carried on midlatitude regions where the majority of long-term measurements are available; and (iii) the low quality of anemometer records as pointed out by the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC).
Global terrestrial stilling | Uncertainties
Measurements started 150 kilometres above Titan's surface, where "Huygens" was blown eastwards at more than 400 kilometres per hour, agreeing with earlier measurements of the winds at 200 kilometres altitude, made over the past few years using telescopes. Between 60 and 80 kilometres, "Huygens" was buffeted by rapidly fluctuating winds, which are thought to be vertical wind shear. At ground level, the Earth-based doppler shift and VLBI measurements show gentle winds of a few metres per second, roughly in line with expectations.
Huygens (spacecraft) | Doppler Wind Experiment (DWE)
The worldwide solar-driven wind results in the so-called Sq (solar quiet) current system in the E region of the Earth's ionosphere (100–130 km altitude). Resulting from this current is an electrostatic field directed E-W (dawn-dusk) in the equatorial day side of the ionosphere. At the magnetic dip equator, where the geomagnetic field is horizontal, this electric field results in an enhanced eastward current within ± 3 degrees of the magnetic equator, known as the equatorial electrojet.
Electrojet | Equatorial Electrojet
In 1883, the eruption of Krakatoa led to visual tracking of subsequent volcanic ash in the stratosphere. This visual tracking led to the discovery of easterly winds between 25 and 30 km above the surface. The winds were then called the Krakatau easterlies. In 1908, data balloons launched above Lake Victoria in Africa recorded westerly winds in the stratospheric levels of the atmosphere. These findings, at the time, were thought to contradict the 1883 findings. However, the winds that would become known as the QBO were discovered to oscillate between westerly and easterly in the 1950s by researchers at the UK Meteorological Office.
Quasi-biennial oscillation | Theory
Winds blowing off the elevated glaciated plateaus of Greenland and Antarctica experience the most extreme form of katabatic wind, of which the Santa Ana is a type, for the most part. The winds start at a high elevation and flow outward and downslope, attaining hurricane gusts in valleys, along the shore, and even out to sea. Like the Santa Ana, these winds also heat up by compression and lose humidity, but because they start out so extraordinarily cold and dry and blow over snow and ice all the way to the sea, the perceived similarity is negligible.
Santa Ana winds | Arctic and Antarctic katabatic winds
There are two wind flow bands that envelope Earth. One is in the southern hemisphere at the latitude of Patagonia, while the other is in the northern hemisphere over Europe. The flow height ranges from 800 meters up to 10,000 meters, while the width is 4,000 or 5,000 km. The average power of the wind is about 2 kW per square meter. High-altitude wind is much more powerful and constant than that at earth level, which is intense in very few places, and at full speed for only about 1,700-1,800 hours per year, which limits the annual production of energy.
KiteGen | High-altitude wind
In the absence of rotation, the wind tends to blow from areas of high pressure to areas of low pressure. The stronger the pressure difference (pressure gradient) between a high-pressure system and a low-pressure system, the stronger the wind. The coriolis force caused by Earth's rotation gives winds within high-pressure systems their clockwise circulation in the northern hemisphere (as the wind moves outward and is deflected right from the center of high pressure) and anticlockwise circulation in the southern hemisphere (as the wind moves outward and is deflected left from the center of high pressure). Friction with land slows down the wind flowing out of high-pressure systems and causes wind to flow more outward (more ageostrophically) from the center.
Anticyclone | Structure
Spring winds can still blow strong, with winds of 28 knots or more encountered about 4 to 8 percent of the time. They do slacken from their winter fierceness, with southerlies and southwesterlies becoming more frequent and northerlies less so as summer approaches. Strong winds are infrequent in summer and mostly associated with thunderstorms. Southerly and southwesterly winds prevail particularly in the north. Southeasterlies are also common in the south, with northerlies also present.
Porte des Morts | Winds
This paradox consists of the fact that helium in the Earth's atmosphere seems to be produced (via radioactive decay of uranium and thorium) faster than it is lost by escaping from the upper atmosphere. The realization that some helium could be ionized, and therefore escape the earth along open magnetic field lines near the magnetic poles (the 'polar wind'), is one possible solution to the paradox. Further research came from the Retarding Ion Mass Spectrometer instrument on the Dynamics Explorer spacecraft, in the 1980s. Recently, the SCIFER sounding rocket was launched into the plasma heating region of the fountain.
Polar wind | Introduction
By 2015 the GFS model had fallen behind the accuracy of other global weather models. This was most notable in the GFS model incorrectly predicting Hurricane Sandy turning out to sea until four days before landfall, while the European Centre for Medium-Range Weather Forecasts' model predicted landfall correctly at 7 days. Much of this was suggested to be due to limits in computational resources within the National Weather Service. In response, the NWS purchased new supercomputers, increasing processing power from 776 teraflops to 5.78 petaflops. In 2018, the processing power was increased again to 8.4 petaflops, The agency also tested a potential replacement model with different mechanics, the flow-following, finite-volume icosahedral model (FIM), in the early 2010s; it abandoned that model around 2016 after it did not show substantial improvement over the GFS.
Global Forecast System | Accuracy
The westerlies explain why coastal North America tends to be wet, especially from Northern Washington to Alaska, during the winter. Differential heating from the Sun between the land which is quite cool and the ocean which is relatively warm causes areas of low pressure to develop over land. This results in moisture-rich air flowing east from the Pacific Ocean, causing frequent rainstorms and wind on the coast. This moisture continues to flow eastward until orographic lift caused by the Coast Ranges, and the Cascade, Sierra Nevada, Columbia, and Rocky Mountains causes a rain shadow effect which limits further penetration of these systems and associated rainfall eastward.
Prevailing winds | Westerlies and their impact
Ships crossing both oceans have taken advantage of the ocean currents for centuries. The Antarctic Circumpolar Current (ACC), or the West Wind Drift, is an ocean current that flows from west to east around Antarctica. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current. In the northern hemisphere, the Gulf Stream, part of the North Atlantic Subtropical Gyre, has led to the development of strong cyclones of all types at the base of the Westerlies, both within the atmosphere and within the ocean. The Kuroshio (Japanese for "Black Tide") is a strong western boundary current in the western north Pacific Ocean, similar to the Gulf Stream, which has also contributed to the depth of ocean storms in that region.
Westerlies | Impact on ocean currents
Wind speeds increase with the distance from the equator, reaching zero values near ±20° latitude, where the troposphere's temperature minimum is located. Closer to the poles, the winds shift to a prograde direction, flowing with Uranus's rotation. Wind speeds continue to increase reaching maxima at ±60° latitude before falling to zero at the poles. Wind speeds at −40° latitude range from . Because the collar obscures all clouds below that parallel, speeds between it and the southern pole are impossible to measure. In contrast, in the northern hemisphere maximum speeds as high as are observed near +50° latitude.
Uranus | Banded structure, winds and clouds
Consider an idealized environment where easterly winds are present at the surface. Ascending through the vertical column, the wind profile strongly veers resulting in calm winds in the mid levels and strong westerlies in the upper levels. A hodograph in this environment would be presented as a straight line (starting to the left (west) of the origin, crossing straight through the origin, then ending some distance to the right (east) of the origin. This environment would produce large amounts of crosswise vorticity (via the right hand rule, vorticity with an axis of rotation perpendicular to the environmental flow). As an updraft begins to form, it will tend to tilt the crosswise vorticity lines into the vertical, resulting in an anticyclonic vorticity axis on the northern fringe and a cyclonic vorticity axis on the southern fringe of the updraft.
Splitting storm | Idealized example
South of the subtropical ridge, surface easterly winds (blowing from east to west) prevail. If the subtropical ridge is weakened by an upper trough, a tropical cyclone may turn poleward and then "recurve", or curve back toward the northeast into the main belt of the Westerlies. Poleward (north) of the subtropical ridge, westerly winds prevail and generally steer tropical cyclones that reach northern latitudes toward the east. The westerlies also steer extratropical cyclones with their cold and warm fronts from west to east.
Atlantic hurricane | Steering factors
For 2018, WindEurope and GWEC launched a global photo competition to capture the power of wind in the run up to Global Wind Day.
Global Wind Day | 2018
Strong winds at Venus's cloud tops circle the planet every four to five earth days. When the poles of Mars are exposed to sunlight after their winter, the frozen CO sublimates, creating significant winds that sweep off the poles as fast as , which subsequently transports large amounts of dust and water vapor over its landscape. Other Martian winds have resulted in cleaning events and dust devils. On Jupiter, wind speeds of are common in zonal jet streams. Saturn's winds are among the Solar System's fastest. Cassini–Huygens data indicated peak easterly winds of . On Uranus, northern hemisphere wind speeds reach as high as near 50 degrees north latitude.
Wind | On other planets
Primary: Secondary:
Classical compass winds | Sources
The low quality in wind speed series is mainly due to non-climatic factors (e.g. observing practice changes, station relocation, anemometer height changes) affecting those records, which result to be unrepresentative of the actual wind speed variations over time. Specific homogenization protocols for wind speed series have been developed in order to detect and adjust potential inhomogeneities.
Global terrestrial stilling | Uncertainties
The basic principles of physics and the Coriolis effect satisfactorily explain that the direction of the wind in the atmosphere is parallel to the isobars. Measurements of wind speed and direction at heights well above ground level confirm that the speed of the wind matches that predicted by considerations of gradient flow, and the direction of the wind is indeed parallel to the isobars in the region. However, from ground level up to heights where the influence of the earth's surface can be neglected, the wind speed is less than predicted by the barometric pressure gradient, and the wind direction is partly across the isobars rather than parallel to them.
Secondary flow | Wind near ground level
Russell’s research explores the role of the ocean in the global climate, focusing on the Southern Ocean and the Southern Hemisphere westerly winds. She uses global climate and earth system models to simulate the climate and carbon cycle of the past, the present and the future, and develops observationally-based metrics to evaluate these simulations. Russell's work on the westerly winds led to her greatest research accomplishment so far: the creation of a new paradigm in climate science, namely that warmer climates produce stronger westerly winds. This insight solved one of the long-standing climate paradoxes, the mechanism responsible for transferring one-third of the carbon dioxide in the atmosphere into the ocean and then back out again during our repeated glacial-interglacial cycles.
Joellen Louise Russell | Career and impact of research
"The Winds of the Globe" had a much more expansive data set than its predecessor. In this book, Coffin aggregates measurements of the “lower strata” from 3223 stations across the world. A summary of the distribution of these stations, as well as the sum of the duration of measurements at each station is reproduced in Table 2. In this case Coffin took six measurements: the mean direction of the lower currents, the ratio that the progressive motion bears to the total distance travelled, modifications that the mean current undergoes in the different seasons of the year, the directions of the forces that cause those modifications, the magnitude of those forces, and finally to show, how and to what degree the winds of the lower strata differ from the higher winds.
James Henry Coffin | "Data"
As such, the current tends to reverse hemispheres seasonally in that basin. The NECC has a pronounced seasonal cycle in the Atlantic and Pacific, reaching maximum strength in late boreal summer and fall and minimum strength in late boreal winter and spring. Furthermore, the NECC in the Atlantic disappears in late winter and early spring. The NECC is an interesting case because while it results from wind-driven circulation, it transports water against the mean westward wind stress in the tropics. This apparent paradox is concisely explained by Sverdrup theory, which shows that the east-west transport is governed by the north-south change in the curl of the wind stress.
Equatorial Counter Current | Introduction
Specifically, the half-winds would be at 22½° on either side of the North, while the principal eight would be at 45° angles from each other. However, an alternative hypothesis is that they will be more equally spaced around 30° from each other. By way of guidance, Aristotle mentions that the easterly and westerly positions are that of the sun as seen on the horizon at dawn and at dusk at different times of the year. Using his alphabetical notation, Aristotle notes that during the summer solstice the sun rises at Z (Caecias) and sets at E (Argestes); during the equinox, it rises at B (Apeliotes) and sets at A (Zephyrus), and finally during the winter solstice it rises at Δ (Eurus) and sets at Γ (Lips).
Classical compass winds | Aristotle
The energetic supply of the platform comes from the wind and the sun, with comets and photovoltaic plates feeding the equipment. The current model consists of four modules and it's configured as a convoy of 10 to 15 meters in length by three wide, with capacity for six people and a load of 2,000 kilos. The project aims at launching an international and / or national scientific program in which the WindSled vehicle will operate as a mobile laboratory that generates zero emissions in the fragile polar ecosystems. At the beginning, it was named 'Polar catamaran', later 'Antarctic Butterfly' and finally Wind Sled.
Ramón Hernando de Larramendi | WindSled (Inuit WindSled)
For instance, the thermal wind associated with pole-to-equator temperature gradients is the primary physical explanation for the jet stream in the upper half of the troposphere, which is the atmospheric layer extending from the surface of the planet up to altitudes of about 12-15 km. Mathematically, the thermal wind relation defines a vertical wind shear – a variation in wind speed or direction with height. The wind shear in this case is a function of a horizontal temperature gradient, which is a variation in temperature over some horizontal distance. Also called baroclinic flow, the thermal wind varies with height in proportion to the horizontal temperature gradient.
Thermal wind | Introduction
The predominant wind direction is from the south-west.
Ilminster | Climate
This can cause sudden change to the wind direction on the island.
Jan Mayensfield | Facilities
It is uncertain when or why the human sense of geographic orientation and direction became associated with winds. It is probable that for ancient settled populations, local physical landmarks (e.g. mountains, deserts, settlements) were the initial and most immediate markers of general direction ("towards the coast", "towards the hills", "towards the lands of Xanadu", etc.). Astral phenomena, in particular the position of the sun at dawn and dusk, were also used to denote direction. The association of geographic direction with wind was another source. It was probably farming populations, attentive to rain and temperature for their crops, that noticed the qualitative differences in winds – some were humid, others dry, some hot, others cold – and that these qualities depended on where the wind was blowing from.
Classical compass winds | Origins
Due to the strong prevailing winds, and shallow water, countries on the North Sea, particularly Germany and Denmark, have used the shore for wind power since the 1990s. The North Sea is the home of one of the first large-scale offshore wind farms in the world, Horns Rev 1, completed in 2002. Since then many other wind farms have been commissioned in the North Sea (and elsewhere). As of 2013 the 630 megawatt (MW) London Array is the largest offshore wind farm in the world, with the 504 (MW) Greater Gabbard wind farm the second largest, followed by the 367 MW Walney Wind Farm.
North Sea | Renewable energy