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Is there a connection between atmoshperic pressure and wind?

Link to the lesson

Before you start you should know
  • the composition and structure of the Earth's atmosphere;

  • the geographical reasons for differences in air temperature near the Earth's surface;

  • that the Coriolis force affects moving objects by making them deviate to the right in the northern hemisphere and to the left in the southern hemisphere.

You will learn
  • to explain the concepts of atmospheric pressure, high pressure, low pressure, wind, thermal convection;

  • to descibe how wind is formed;

  • to characterise a cyclone and an anticyclone.

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Nagranie abstraktu
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Present all the items related to atmospheric pressure.

Atmospheric pressureatmospheric pressureAtmospheric pressure is where a body of air causes pressure on a cetain part of the Earth's surface. It can be logically stated that atmospheric pressure is lower in the mountains and higher at sea level. This is indeed the case.

The level of atmospheric pressure varies, not only depending on height above sea level. At various parts of the globe, located near the surface of the Earth, different pressure levels can be found. In these locations, where the pressure is higher than in surrounding areas, we are speaking about high atmospheric (barometric) pressure. On the other hand, where the pressure is lower than in surrounding areas, we are speaking about low atmospheric (barometric) pressure. The difference in pressure causes air to move from high to low. Wind is caused by horizontal or near horizontal air movement, resulting from the difference in pressure.

If not for the phenomenon known as the Coriolis force (see: Earth's rotationixr5Y2Lxy7Earth's rotation, question 3. Consequences of rotation), winds would blow radially from high pressure areas to low. However, the Coriolis force causes the wind to turn (to the right in the northern hemisphere and to the left in the southern hemisphere) and away from centres of high pressure. It also moves clockwise (in the northern hemisphere) and anti‑clockwise (in the southern hemisphere). This is different to low pressure systems, which are masses of air where the pressure is lower than that surrounding them. The wind blows towards the centre of the low, but because of the Coriolis force it starts to turn and blow in a counter‑clockwise direction (in the northern hemisphere) or clockwise (in the southern hemisphere). Low pressure systems where winds blow spirally (due to the Coriolis force) towards their centres, are known as cyclones cyclonescyclonecyclones, and high pressure systems with spiral winds blowing outside are anticyclones – anticyclonesanticycloneanticyclones.

The dynamics and movement of barometric pressure systems can be shown on climatic maps. To do this, pressure is measured in many locations, and then places with the same reading are connected. The lines created in this way are called isobars.

Vertical, or near‑vertical movements of air in the atmosphere, which come about as a result of heat near the surface of the earth, we call thermal convection. Convection is the movement of air upwards (warm air rises) and downwards (cold air falls). Although these are movements of air, we do not refer to them as winds.

In the northern hemisphere the winds blow from the barium upwardly in a clockwise direction, and towards the lowlands contrary to their movement. On the other hand, in the southern hemisphere the winds blow from the barium bump anticlockwise, and towards the low tide according to it.

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Ilustracja przedstawia mapę świata i obrazuje cyrkulację powietrza w styczniu, World air circulation in January. Na mapie zaznaczono izobary, wartości ciśnienia atmosferycznego zredukowane do poziomu morza (skala od 990 do 1040 hektopaskali), isobars (atmospheric pressure reduced to sea level). Obszary o wysokim ciśnieniu położone są w Ameryce Północnej, na Grenlandii, w północnej, środkowej i wschodniej części Azji oraz na oceanach w pobliżu obu zwrotników. Obszary o niskim ciśnieniu atmosferycznym położone są na Antarktydzie i otaczających ją wodach aż do krańcowych punktów Ameryki Południowej, Afryki i Australii, obejmują całą Amerykę Południową, środkową i południową część Afryki , Australię i Oceanię, Islandię i Aleuty. Literami W opisano ośrodki wysokiego ciśnienia, high pressure center, literami N opisano ośrodki niskiego ciśnienia. Podano również nazwy ośrodków wysokiego i niskiego ciśnienia, low pressure center. Na mapie opisano izobary co pięć hektopaskali. Strzałkami oznaczono przeważający kierunek wiatru, the prevailing wind direction. Układają się one w różnych kierunkach. Przerywaną linią zaznaczono strefę zbieżności pasatów, the zone of convergence of trade winds. Przebiega ona nieco poniżej równika. Opisano pasaty – wzdłuż strefy zbieżności pasatów oraz monsuny – na południowo-wschodnim wybrzeżu Azji.
The system of atmospheric pressure centers and the prevailing wind directions on Earth in January.
Source: licencja: CC BY 3.0.
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Exercise 1
Finish the sentence: Coriolis force... Możliwe odpowiedzi: 1. change the direction of the winds blowing on Earth., 2. the winds blow clockwise in the northern hemisphere., 3. in the southern hemisphere the winds blow in a counterclockwise direction., 4. occurs only in Europe.

Summary

  • Atmospheric pressure varies according to altitude.

  • Wind is the horizontal movement of air from high to low pressure areas.

  • The Coriolis force changes the direction of winds blowing on the Earth. In the northern hemisphere, winds from the centre of high pressure systems blow in a clockwise direction, and in the southern hemisphere they blow anti‑clockwise. On the other hand, winds coming from the centre of low‑pressure systems in the northern hemisphere blow anti‑clockwise, and clockwise in the southern hemisphere.

  • Winds blow everywhere on the Earth. They change on a yearly or daily basis, or can be localised.

Keywords

pressure, wind, isobars, cyclones, anticyclone

Glossary

anticyclone
anticyclone
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Nagranie słówka: anticyclone

antycyklon - układ wiatrów w obrębie wyżu barycznego (wieją po liniach spiralnych od środka na zewnątrz wyżu); na półkuli północnej mają kierunek zgodny z ruchem wskazówek zegara, a na południowej przeciwny do tego ruchu

atmospheric pressure
atmospheric pressure
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Nagranie słówka: atmospheric pressure

ciśnienie atmosferyczne - siła, z jaką słup powietrza naciska na określoną jednostkę powierzchni Ziemi

cyclone
cyclone
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Nagranie słówka: cyclone

cyklon - układ wiatrów w obrębie niżu barycznego (wieją po liniach spiralnych od zewnątrz do środka niżu); na półkuli północnej mają kierunek przeciwny do ruchu wskazówek zegara, na południowej zgodny z ruchem wskazówek zegara