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Is there a relationship between the atmospheric pressure and the wind?

Atmospheric pressureatmospheric pressureAtmospheric pressure is the force with which the air column presses on a specific unit of the Earth's surface. By using logic, it can be stated that in the mountains the atmospheric pressure is lower and at the sea level higher. And indeed it is.

The value of atmospheric pressure varies not only depending on the altitude above the sea level. In various places on the globe near the Earth's surface, we find different pressure values. The pressure difference causes the air to move from the higher to the lower. Horizontal or close to the horizontal air movement resulting from the pressure difference is called wind.

The Sun’s uneven illumination of the Earth leads to varied heating of our planet’s surface. Unequal thermal distribution causes local and global movement (circulation) of air. Below, we present Earth’s global air circulation. Please bear in mind that this is only a theoretical description. In a real‑life model, global circulation would be significantly impacted by land, oceans, substantial elevation differences, ocean currents and changing seasons, which are unevenly distributed across the Earth’s surface.

On the equinoxes, the Sun heats the Equator most intensely. Heat causes the air to expand and become lighter. It also causes upward vertical movement of the air (thermal convection) to altitudes of a few or even 11–19 kilometres. At the equator, a low‑pressure zone is created. In this area, a vertical hot air movement is dominant and a surface wind is very weak. That’s why this region is referred to as equatorial calms or doldrums (and is also called the Intertropical Convergence Zone, ITCZ). Air cools down with altitude, causing water vapour to condense and water droplets to fall to the Earth as heavy zenithal (tropical) rain. Moisture‑free and very cold air masses split into two currents and, at an altitude of 12–18 km, move north and south, towards the Tropics. At the Tropics, the cold and condensed air becomes so heavy that it drops to the Earth’s surface. Due to an increase in the atmospheric pressure, the air becomes hot and even drier during its convectional descent. As a result, there isn’t any precipitation near the Tropics. A high‑pressure zone is formed at the Tropics. Some of the air moves back to the Equator, and the rest flows to temperate climate zones. At the poles, cold air drops and generates high atmospheric pressure. Next, it flows down towards the polar circles, and even reaches the temperate climate zone with its ever‑fluctuating pressure patterns.

Constant winds. Winds periodically changeable

Differences in atmospheric pressure and altitude occur on Earth very commonly. There are winds everywhere. They can be permanent, periodically variable or local. Permanent winds are those that result from global air circulation. Trade winds - permanent winds in the tropic zone, blowing from the tropics to the equatorial zone of silence with a deviation caused by the rotation of the Earth. Under the influence of the Coriolis force, they blow in the northern hemisphere from the north‑east direction and in the south from the south‑east. Antipasies - winds blowing from the equator to the tropics, but at the height of several or a dozen or so kilometers. Under the influence of the Coriolis force in the northern hemisphere, they blow from the south‑west and south from the north‑west. It should be added that according to the latest descriptions of the general circulation of the atmosphere, the term „antasnatch” is no longer used for the flowing air from the equator towards the higher latitudes.

The western winds are also constant - blowing from the tropics towards the Arctic Circle in both hemispheres and eastern winds blowing from both poles to the Arctic Circle.

Temporary changeable wind is monsoon. Its creation results mainly from the change of seasons and the accompanying differences in the intensity of heating the land and the ocean. In summer, large continents (especially Asia) heat up much stronger than the neighboring oceans (especially the Indian Ocean and Pacific Ocean). The land is much warmer over the land, the air rises and produces a powerful than baric, while above the cooler ocean a high bar is created. The wind called the summer monsoon blows from the ocean and brings precipitation. In winter, the land is colder because it loses heat faster than the oceans, so the dry winter monsoon blows off the coast towards the ocean.

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Ilustracja przedstawia kierunki wiatru i wielkość opadów w rejonie Azji Południowej i Południowo-Wschodniej w zimie i w lecie. Z lewej strony przedstawiono monsun zimowy - winter monsoon - wiejący od grudnia do lutego - February to December. Oznaczono małe opady, ukazano wyż W nad lądem, a niż N nad morzem. Wiatr wieje z lądu w kierunku morza co zaznaczono grubą strzałką i dużą ilością małych strzałek. Z prawej strony przedstawiono monsun letni - Summer Monsoon, który wieje od czerwca do sierpnia - June to August. Oznaczono opady, opisano niż N nad lądem i wyż W nad morzem. Wiatr od morza w kierunku lądu zaznaczono grubą strzałką i dużą ilością małych strzałek.

Local winds

Geographers distinguish dozens of local winds. A typical example is the breeze, that is the wind blowing on the edges of every sea, and even larger lakes. The sea (onshore) breeze blows from the cooler sea (where a higher pressure is generated locally) towards the warmer land (where the atmospheric pressure is lower) during the day. The land (offshore) breeze is formed when the land loses heat at a faster rate than water (atmospheric pressure is higher over land than over water). It blows from the cooled land to the warmer sea at night. The range of this wind is usually a few kilometers.

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Grafika przedstawiająca wiatr dzienny - onshore breeze. Grafika ukazuje fragment wybrzeża. Po lewej stronie widoczne jest morze, a po prawej - ląd. Z lewej strony oznaczona jest strefa wyższego ciśnienia - High. Strzałki pokazują obieg powietrza od strefy nad wodą z wyższym ciśnieniem - High - do strefy z niższym ciśnieniem - Low.

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Grafika przedstawiająca wiatr nocny. W prawym górnym rogu widać róg księżyca. Przedstawiony jest fragment wybrzeża nocą przy rozgwieżdżonym niebie. Nad morzem oznaczony jest obszar niskiego ciśnienia - Low, a nad lądem obszar wyższego ciśnienia High. Strzałki pokazują obieg powietrza między strefą niskiego i wysokiego ciśnienia.

Another example of local winds is fen. This wind in Poland is called halny. However, in the mountains around the world it has a variety of names. It is formed when there is a difference in atmospheric pressure on two sides of high mountains. The air masses rise and at the same time cool down by 0.6°C for every 100 m. The water vapor condenses and falls in the form of rain or snow. Cold air exceeds the mountains and begins to fall on the opposite side, but because it is already dry, it warms up by 1°C for every 100 m, so it becomes warmer than at the same height on the other side of the mountains. Fen winds are very violent and gusty, and when they occur in winter, they can quickly melt even a thick snow cover. Local winds with different names are also created on the border of extensive plateaus, in wide valleys, near glaciers and ice sheets and on the border of deserts.

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Grafika przedstawia mechanizm powstawania fenu wraz z przykładami, jak działa on na środowisko. Na ilustracji przedstawiona jest góra z wierzchołkiem oraz jej dwie strony - nawietrzna i zawietrzna. Po stronie nawietrznej opis High, występuje opad i w miarę wzrostu wysokości spada temperatura z 10 stopni Celsjusza do -4,4 stopni Celsjusza: the air temperature falls by 0,6 stopnia Celsjusza on 100 metres. Po stronie zawietrznej opis Low, w miarę spadku wysokości temperatura rośnie, osiągając 19,6 stopnia Celsjusza: the air temperature rises by 1 stopień Celsjusza on 100 metres. Wysokość góry to 3000 metrów nad poziomem morza. Podnóże góry ma wysokość 600 metrów nad poziomem morza.

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Fotografia przedstawiająca skutki wiatru halnego. Spory fragment zbocza wzniesienia z połamanymi drzewami iglastymi.

Summary

• Wind is the level of air movement from high to low.

• The Coriolis force changes the direction of the winds blowing on Earth. In the northern hemisphere the winds from the center of the barium are blowing clockwise, and in the southern hemisphere, contrary to the movement. On the other hand, winds blowing inside the low‑pressure barnacles in the northern hemisphere blow counter‑clockwise and in the southern hemisphere in accordance with it.

• Differences in the Earth's lighting by the Sun cause global air circulation.

• Winds blow everywhere on Earth. They change on a yearly or day scale or have a local character.

Keywords

air circulation, wind, atmospheric pressure, monsoons, fen, breeze

Glossary