22.3 Atmospheric Circulation

It all starts with unequal heating of Earth that cause differences in pressure – resulting in air movement Warm air is less dense, rises and creates LOW pressure Cold air is more dense, sinks towards Earth’s surface and creates HIGH pressure. Air flows from poles (H) to equator (L)

Wind blows from areas of to areas of high pressure low pressure

Air near Earth’s surface flows from the poles to the equator because of the spin of the Earth. Earth’s diameter is greatest at the equator and smaller at the poles. The equator must travel faster to complete one rotation than the poles. The air moves more slowly than the ground beneath it does. This causes the air to flow from the poles toward the equator.

High pressure regions form where cold air sinks towards Earth’s surface. Low pressure regions form where warm air rises away from Earth’s surface.

Circulation of the atmosphere and of the oceans is affected by the rotation of Earth on its axis. Earth’s rotation causes its diameter to be greatest through the equator and smallest through the poles. Points bear the equator travel further in a day.

Coriolis Effect Moving objects follow a curved path due to Earth’s rotation. Deflected right in northern hemisphere (Clockwise) Deflected left in southern hemishphere (Counterclockwise) Detectable only on objects that move very fast or over long distances.

Global Winds – 3 looping patterns called wind belts Wind flows from poles to equator in convective cells. Each cell correlates to a wind belt that forms wind that flows one way. (prevailing wind) Wind is named for the direction it come from.

Winds that blow from E to W from 30 Winds that blow from E to W from 30* latitude to the equator are the trade winds. In the N Hemisphere, trade winds flow from the northeast. Prevailing winds that blow W to E are the westerlies. Winds from 60-90* E-W are the easterlies. Stormy regions where easterlies meet westerlies are fronts.

Doldrums – form at equator where the warm air moves upward and there is little wind. Horse Latitudes –form at 30 degrees N and S where the air decends and there is little wind

Jet Stream Narrow band of strong wind that blows in the upper troposphere

Air movement caused by local conditions & temperature are local winds. Breeze – gentle winds that extend over distances of less than 100km

Local Wind – not part of global wind belts Sea Breeze – cool wind moving from water to land in afternoon H L Warm Land Cool Water Land Breeze – cool wind moving from land to water at night H L Cool Land Warm Water

Valley Breeze – warm air from the valley moves upslope during day Mountain Breeze Mountain Breeze – cool air descends from mountain peak at night