Earth's atmospheric circulation

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Animation showing the main circulatory patterns in the Earth's atmosphere. The primary driver of this circulation is solar heating, which is strongest at the equator. The view from the surface looks east along the equator. Solar heating causes warm, less dense air to rise (red arrows), forming an area of low atmospheric pressure. The rising air takes moisture to higher levels, which condenses and falls as rain as the air cools. Most equatorial regions experience frequent thunderstorms and high levels of rainfall, and rainforests are often found in this region. The rising air cools until it reaches the tropopause, where its rise is halted as temperatures begin to rise above the tropopause. The rising dry air spreads out north and south, becoming cooler and denser, until it is dense enough to descend to Earth. The descending dry air creates bands of high pressure around 30 degrees north and south, and the low rainfall in this region typically produces deserts. These two rotational cells in the tropics are called the Hadley cells. The other primary drivers of circulation are the polar highs. The intense cold of the polar regions causes cold, dense air to descend, forming a permanent region of high pressure that spreads out equator-wards, to around 60 degrees north and south. Between the polar and Hadley cells is the temperate zone, a region of much less stable weather. Cold descending air from the Hadley cell spreads polewards along the ground, warming up as it does so. When it meets the cold polar air it is forced upards, driving a third circulatory cell. The rotation of the Earth causes descending air to be deflected westwards when it is moving equatorwards and eastwards when it move polewards - this is called the Coriolis effect. This causes the formation of permanent wind patterns, notably the trade winds, mid-latitude westerlies, and the polar easterlies. For a version of this clip with the winds and lines of latitude labelled, see K003 1869.
Licence : Droits gérés
Crédit : Science Photo Library / Settle, Johnny
Model Release : Non requis
Property release : Non requis
Durée : 30 Secondes
Aspect ratio : 16/9
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