Post on 01-Apr-2015
transcript
22.3Atmospheric 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)
• 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* 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
Land Breeze – cool wind moving from land to water at night
Sea Breeze – cool wind moving from water to land in afternoon H
H
L
L
Warm Land
Cool Water
Cool LandWarm Water
Valley Breeze – warm air from the valley moves upslope during day
• Mountain Breeze
Mountain Breeze – cool air descends from mountain peak at night