Chapter 6 Flashcards
Driving force behind wind
Winds are driven by:
The imbalance between equatorial energy surpluses and polar energy deficits
Air Pressure
Air molecules create air pressure through their motion, size and number. this pressure is exerted on all surfaces in contact with air.
Winds are named for the direction from ________
which they originate!
Barometer
Any instrument that measures air pressure
Gravity _______ air, making air denser closer to the Earth’s surface.
compresses
Types of Barometers
Mercury
Aneroid
Density is _____ near Earth’s surface, and ______ with altitude.
Density is higher near Earth’s surface, and decreases with altitude.
Mercury Barometer
- A device that measures air pressure using a column of mercury in a tube
- One end of the tube is sealed, the other end is inserted in an open vessel of mercury
- if the pressure is high the air pressure will push the liquid mercury and the higher the mercury will rise inside that glass tube
Aneroid Barometer
An instrument that measures air pressure without liquid.
A small chamber is partially emptied of air and sealed and connected to a mechanism attached to a needle on a dial.
As the air pressure outside the chamber increases, it presses inward on the chamber, causing changes in the chamber that move the needle.
Normal sea-level pressure
760 mm mercury
- 2 mb (millibars)
- 32 kPa (kiloPascals)
Anemometer
An instrument that measure wind velocity.
Atmospheric/Barometric pressure
Weight of an atmospheric column (body of air above a specified area) as described as force per unit area.
Wind Vane
An instrument that measures wind direction
Wind’s two principal properties
Speed and Direction
Isoline
A line along which there is a constant value
Isobar
An isoline connecting all points of equal atmospheric pressure.
The pattern of isobars provides a portrait of?
the pressure gradient between an area of higher pressure and one of lower pressure
The spacing between isobars indicates?
The intensity of the pressure difference, or pressure gradient.
Why use mercury in a barometer?
Mercury is about 14 times denser than water
Factors Affecting Wind (4)
Gravity
Pressure Gradient Force(PGF)
CoriolisForce (CF)
Friction Force (FF)
Wind
The horizontal motion of air across Earth’s surface.
Wind is produced by…
Differences in air pressure (Density) between one location and another.
Millibar
a measure of force per square metre of a surface area.
High pressure is associated with…
Diverging and descending air
Cold, Dry, Dense air
Low pressure is associated with…
Converging and rising air
Warm, humid, less-dense air
Why do High and Low pressure areas occur on Earth?? How does this affect wind
Earth is unequally heated.
Cold, dry, dense air at the poles exerts greater pressure than warm, humid, less-dense air along the equator
When masses of air are near each other, a pressure gradient develops and leads to horizontal air movement
Another word for wind
Atmospheric Circulation
How does GRAVITY affect wind?
- The pressure that Earth’s gravitational force exerts on the atmosphere is virtually uniform
- Gravity equally compresses the Earth’s atmosphere, with density decreasing as altitude increases
- The gravitational force counteracts the outward centrifugal force acting on Earth
- Without gravity, there would be no atmospheric pressure—or atmosphere, for that matter
How does PRESSURE GRADIENT FORCE affect wind?
Drives air from areas of higher barometric pressure to areas of lower barometric pressure, causing winds.
How does CORIOLIS FORCE affect wind?
The force that is a result of the Earth’s rotation (the Coriolis Effect) acts at 90 degrees to the right (NH)/ left (SH) left of the direction of the wind.
- This force increases as latitude increases
How does FRICTION FORCE affect wind? (effects)
Decreases Wind Speed
Reduces Effectiveness of Coriolis Force
Causes winds to move across isobars at an angle
Friction Force
The effect of drag by the wind as it moves across a surface, operative through 500 m of altitude. Surface friction slows the wind and therefore reduces the effectiveness of the Coriolis force.
Coriolis Force
The Coriolis force deflects anything that flies or flows across Earth’s surface from a straight path. Because Earth rotates eastward, such objects appear to curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
Because the speed of Earth rotation varies with latitude, the strength of this deflection varies, being weakest at the equator and strongest at the poles.
Friction force varies by…
surface texture
wind speed
time of day and year
atmospheric conditions
How does water vapour in air affect density?
- Moist air is lighter
- Because the molecular weight of water is less than that of the molecules making up dry air
- As water vapour in the air increases, density decreases, so humid air exerts less pressure than dry air.
What does Earth’s atmospheric circulations (wind) transfer?
- thermal energy
- air
- water masses
using:
- waves
- streams
- eddies
Geostrophic Wind
A wind characteristic of upper tropospheric circulation, moving between areas of different pressure along a path parallel to the isobars.
Products of the pressure gradient force and the coriolis force.
Geostrophic Winds are products of
The pressure gradient force
The Coriolis Force
Sea Breeze
High pressure over water, low pressure over land.
Wind blows towards the land. generally during the day.
Land Breeze
Low pressure over water, low pressure over land.
Wind blows towards the sea, generally occurs during the night.
Land Vs Water in terms of rate of cooling
Land cools faster
Katabatic wind
Only happens in Antartica and Greenland.
cold, permanent snow/ice on land masses surrounded by water. Cold, fast air tends to sink toward the warm ocean. this is due to the pressure gradient being very high.
(wind chill of -125)
“Cells” names
Polar Cell Ferrel Cell Hadley Cells Ferrell Cell Polar Cell
“Winds” names
NE Polar Easterlies SW Westerlies NE Tradewind SE Tradewind NW Westerlies SE Polar Easterlies
Polar Cells
60-90° circulations
Ferrell Cells
30-60° circulations
Hadley Cells
0-30° circulations
Global Barometric Pressure in January (Vancouver)
The polar jet stream carries storms from the low pressure (Aleutian Low) system off the coast of Vancouver, causing wet rainy winters.
Aleutian Low
The low pressure system responsible for the winter storms in the Northern Pacific (carried towards Vancouver)
Icelandic Low
The low pressure system that generates all the winter storms over the North Atlantic Ocean, which are then carried towards western Europe.
Pacific/Hawaiian High
The high pressure system responsible for the sunny summer weather in the Northern Pacific (then carried towards Vancouver)
Bermuda High
The high pressure system responsible for the sunny summer weather in the Northern Atlantic (then carried towards Western Europe)
Local Winds (small scale) (5)
Sea Breeze
Land Breee
Valley
Sea Breeze ?
Higher pressure over water, lower pressure over land (which heats up faster).
Wind blows towards the land. generally during the day.
Land Breeze ?
Low pressure over water, low pressure over land.
Wind blows towards the sea, generally occurs during the night.
Valley Breeze
As air becomes warmer during the day, warm air rises up from a valley (during the day).
Mountain Breeze
As air cools during the night, the colder air sinks down into the valley (during the night)
Winter Monsoon
High pressure develops over continental Asia, with wind flowing down to low pressures. Associated with cold and dry air.
Summer Monsoon
Wind is going from the ocean to the continent. Warm and wet conditions.
Chinooks
-`
Types of Major Ocean Currents
Warm Currents
Cold Currents
Warm ocean Currents (direction)
lower latitudes towards higher latitudes
Cold Ocean currents (direction)
higher latitudes towards lower latitudes
Coupling Effect
Interaction between the ocean currents and atmospheric circulations
