Lecture 5 Flashcards
What is the Hadley cell?
The hypothetical model of air circulation in the atmosphere. It states that there is one cell that rises at the equator and falls at the poles.
Why is the Hadley cell only hypothetical?
It only works if the earth is not rotating, an made of uniform material. Which is not true
What is the three cell atmospheric circulation model?
Three cells of rising air away from the equator to the poles.
What are the three cells in the atmospheric circulation model?
Hadley: from the equator
Ferrel: mid latitude
Polar: drops at the poles
What two things complicate the 3 cell model?
Different thermal response of oceans and land.
Earths tilt and season change and rotation.
What are some effects of three cell model atmospheric circulation?
North and south hemisphere
Semi permanent high and low pressure zones.
Major feature shift seasonally due to sun angle
What creates wind? (2)
Movement of air masses due to pressure differences.
Different heating due to changing Insolation
Pressure moves from a _______ to _______ pressure zone.
High, low
What makes wind a vector?
It has a magnitude and direction.
True or false:
Wind is named for the location it moves in.
False, wind is named for its origin
Ex) wind from the west is westerlies
What do isobars show?
Pressure gradients
What are four driving forces of wind?
Pressure gradient force (PGF)
Coriolis force
Centripetal force
Friction
True or false:
Pressure gradient force only effects global scale wind patterns.
False, it drives both global and local winds.
What is pressure gradient force driven by?
Different pressures and air masses moving high to low.
What causes Coriolis force?
Earths rotation.
In the Northern hemisphere wind is deflected to the _________ and in the Southern Hemisphere to the ________.
Right, left
Cyclones in the northern hemisphere rotate ____________.
Counterclockwise
True or false:
In the Southern Hemisphere air masses rotate clockwise.
True
What causes geostrophic winds?
Pressure gradient force and Coriolis force.
What direction do geostrophic winds move? And why?
They move parallel to contures due to Coriolis force.
The closer to earths surface the ________ impact Coriolis force has.
Less
What is centripetal acceleration?
Inward force perpendicular to the path of motion.
True or false:
Centripetal acceleration contributes to circular rotation around high and low pressure zones.
True
What three driving forces of wind cause gradient wind?
Pressure gradient force
Coriolis force
Centripetal acceleration
What is gradient wind?
The flow of at around a high or low pressure zone.
What is friction?
The drag force, creates when two things come in contact and their interaction causes a deceleration.
How does friction effect atmospheric circulation?
Earths surface slows wind down in low altitudes creating atmospheric drag. Also creates a boundary layer.
What forces create circulation in surface winds?
Pressure gradient force
Coriolis force
Centripetal acceleration
Friction force
In low pressure zones surface wind is _________ and so wind is moving ________
Converging, upward
True or false:
Wind in a high pressure zone is diverging from the centre and pulling wind down.
True
What is an air mass?
A large body of air of the same temperature and humidity.
What is more dry, a continental air mass or a Maritime air mass?
Continental
What is the one cell model when looking at atmospheric circulation?
Hadley cell
What is subsidence?
The divergence from the centre of a high pressure zone
What is a cold front?
A cold air front meeting and colliding with warm air
What is the result of a cold front?
Rapid uplift creating more violent weather
True or false
A cold front raises over the top of a warm front when they come into contact.
False
What is a warm front?
A warm front coming in contact with a cold front and gradually easing over the top.
True or false
Warm fronts creates less violent weather than cold fronts.
True
What is an occluded front?
When one cold front catches another pushing up a warm front.
Define cyclogenesis.
Winds moving around a pressure zone, slowly the cold front will catch the cold front and over take it.
Resulting in an occluded front.
True or false
Warm front move faster than cold fronts
False
Name the three main types of storms.
Extra-tropical (mid-latitude) cyclones
Tropical cyclones
Meso-scale
What direction do extra-tropical storms move?
West to east, across Canada.
Where do extra-tropical cyclones normally occur?
Mid-latitude
What makes a extra-tropical cyclone?
A strong temperature gradient
Lots of available moisture
Upper air contributions.
What is the Intertropical Convergence Zone?
A zone of low atmospheric pressure located at the equator due to global wind convergence and convection from heating.
What is cyclogenesis?
Warm and cold air masses moving around a low pressure zone eventually the cold front over takes the warm front and creates an occluded front.
What direction do cyclones travel?
East
True or false
ITCZ is stationary year round
False, it migrates seasonally
