why does air move through the atmosphere

Even with disruptions like
weather fronts and storms, there is a consistent pattern to how air moves
around our planetвs atmosphere. This pattern, called atmospheric circulation,
is caused because the Sun heats the Earth more at the equator than at the poles. It's also affected by the spin of the Earth. In the tropics, near the
equator, warm air rises. When it gets about 10-15 km (6-9 miles) above the Earth
surface it starts to flow away from the equator and towards the poles.


Air that
rose just north of the equator flows north. Air that rose just south of the
equator flows south. When the air cools, it drops back to the ground, flows
back towards the Equator, and warm again. The, now, warmed air rises again, and
the pattern repeats. This pattern, known as
convection, happens on a global scale. It also happens on a small scale within individual storms.


But because Earth is spinning, the air that moves north and south from the equator also turns with the spin of the Earth. Air going north turns to the right. Air traveling south turns to the left. The power of Earthвs spin to turn flowing air is known as the Coriolis Effect. If the Earth didnвt spin, there would be just one large convection cell between the equator and the North Pole and one large convection cell between the equator and the South Pole.


But because the Earth does spin, convection is divided into three cells north of the equator and three south of the equator. Because the air at the poles is cooler than the air at lower latitudes, it has a tendency to move toward the equator. It doesn't move in a straight line, however, because the Earth's rotation exerts a tangential force called the Coriolis force.


The effect of this force isn't straightforward. It bends winds at the poles toward the west, but between 30 and 60 degrees latitude, it bends them in the opposite direction, creating the westerlies. In the upper troposphere, the westerlies can blow at speeds of 160 kilometers per hour (100 miles per hour). These upper tropospheric winds are known as the jet streams.

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