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Above 60°N, the polar cells circulate polar air toward the equator. Air rises near the polar front, and moved toward the poles. As it sinks at the poles, the cold air is deflected by the Coriolis Force, so that surface winds are easterly, commonly called the polar easterlies. Similarly to the Hadley Cell, the Polar Cell is a thermally direct circulation.

Around 50°-60° N is typically where the polar jet is located and like the subtropical jet stream,the winds can range from 80 -140 mph, but sometimes can reach as high as 275 mph. The exact position of the polar jet stream will vary, depending on the locationof the boundary between cold, polar and temperate air. During the winter months in each hemisphere, the polar jet stream is more pronounced due to the large differences in temperature from the equator to the poles.

Ferrel Cell (Indirect Thermal or Mid-latitude cells): Not all of the air that falls to the surface at 30°N flows toward the equator as part of the Hadley Cell, some of it moves toward the poles. The air is deflected to the east from the Coriolis Force, causing the air to more or less flow from the west. These winds are commonly referred to as the westerlies. Areas of high and low pressure break up this flow pattern from time to time.

The air is still warm as it travels toward the poles, and around 60°N it rises and returns to 30°N to complete the circulation. This warm air also encounters cold air descending from the poles, and the two air masses do not mix and become separated by a boundary known as the polar front.

At roughly 30°N, surface high pressures (known as sub-tropical highs) the air to sink. Since air flowing northward from the equator is warmer and moister than the air closer to the poles in the upper atmosphere, the strong temperature gradient forms a jet stream. This particular jet stream is known as the subtropical jet and it flows from west to east in both hemispheres.

At the surface, some of the air that sinks returns toward the equator and produces northeast (southeast) trade winds in the Northern (Southern) Hemisphere.

18th century English lawyer and amateur meteorologist, George Hadley created an early theory for atmospheric circulation, which included the rotation of the earth. His theory was based the idea of one circulation cell that was driven by the Sun’s energy (direct thermal cell). Strong solar heating in the equatorial latitudes caused a general rising motion with warm air moving toward the poles, where it would cool and sink. At the lower levels, the air would flow back to the equator to replace the rising air.

The Hadley Cell circulation takes places in the upper atmosphere from the equator to about 30°N/S. Over the equatorial waters, the air is warm and moist, and the horizontal pressure gradients are weak. This causes winds in the regions to be light.

Below 60°S, the polar cells circulate polar air toward the equator. Air rises near the polar front, and moved toward the poles. As it sinks at the poles, the cold air is deflected by the Coriolis Force, so that surface winds are easterly, commonly called the polar easterlies. Similarly to the Hadley Cell, the Polar Cell is a thermally direct circulation.

Around 50°-60° S is typically where the polar jet is located and like the subtropical jet stream,the winds can range from 80 -140 mph, but sometimes can reach as high as 275 mph. The exact position of the polar jet stream will vary, depending on the locationof the boundary between cold, polar and temperate air. During the winter months in each hemisphere, the polar jet stream is more pronounced due to the large differences in temperature from the equator to the poles.

Ferrel Cell (Indirect Thermal or Mid-latitude cells): Not all of the air that falls to the surface at 30°S flows toward the equator as part of the Hadley Cell, some of it moves toward the poles. The air is deflected to the east from the Coriolis Force, causing the air to more or less flow from the west. These winds are commonly referred to as the westerlies. Areas of high and low pressure break up this flow pattern from time to time.

The air is still warm as it travels toward the poles, and around 60°S it rises and returns to 30°S to complete the circulation. This warm air also encounters cold air descending from the poles, and the two air masses do not mix and become separated by a boundary known as the polar front.

At roughly 30°S, surface high pressures (known as sub-tropical highs) the air to sink. Since air flowing northward from the equator is warmer and moister than the air closer to the poles in the upper atmosphere, the strong temperature gradient forms a jet stream. This particular jet stream is known as the subtropical jet and it flows from west to east in both hemispheres.

At the surface, some of the air that sinks returns toward the equator and produces northeast (southeast) trade winds in the Northern (Southern) Hemisphere.

18th century English lawyer and amateur meteorologist, George Hadley created an early theory for atmospheric circulation, which included the rotation of the earth. His theory was based the idea of one circulation cell that was driven by the Sun’s energy (direct thermal cell). Strong solar heating in the equatorial latitudes caused a general rising motion with warm air moving toward the poles, where it would cool and sink. At the lower levels, the air would flow back to the equator to replace the rising air.