Chapter 6 Flashcards
Driving force behind wind
Winds are driven by: the imbalance between equatorial energy surpluses and polar energy deficits
Atmsopheric Circulation is Categorized at ___ levels.
3 levels
- primary circulation
- secondary circulation
- tertiary circulation
Primary circulation
consists of general worldwide circulation (saharan dust for example)
Secondary Circulaton
consists of high pressure and low pressure systems
Tertiary Circulation
consists of local winds and temporal weather patterns
Meridional flows
Winds moving principally North or South along meridians of longitude
Zonal Flows
Winds moving East or West along parallels of latitude
Air Pressure
weight of the atmosphere described as force per unit area
- air molecules create air pressure through their motion, size and number. this pressure is exerted on all surfaces in contact with air.
Wind
- The horizontal motion of air across Earth’s surface
- produced by differences in air pressure (Density) between one location and another produce wind
Winds are named for the direction from ________
which they originate!!!
Driving Forces behind wind speed and direction of wind within the Atmosphere
- Earth’s Gravity
- Pressure Gradient Force
- Coriolis Force
- Friction Force
Pressure and Density _____ with altitude
decrease
Why does the experience of “thin air” occur?
caused by the smaller amount of oxygen to inhale. (fewer air molecules mean less oxygen)
Symptoms of acute mountain sickness (thin air)
- shortness of breath
- headaches
- disorientation
Why is hot air less dense than cold air?
- Heating air increases molecular activity and temperature.
- Increase in molecular activity results in greater spacing between molecules, decreasing density and air pressure
- cold air is heavy and dense, so sinks and increases pressure
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.
warm, humid air is associated with _____ p____ and cold, dry air is associated with ______ p____
warm, humid air is associated with low pressure
and cold, dry air is associated with high pressure
Another word for wind
Atmospheric Circulation
Barometer
Any instrument that measures air pressure
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
Millibar
a measure of force per square metre of a surface area.
Standard of normal sea-level pressure
at 1013.2 mb or 29.92 in. of mercury (Hg).
In Canada and other countries, normal air pressure is expressed as
Standard of normal air pressure in Canada and some other countries is expressed as
101.32 kPa (kilopascal; 1 kPa = 10 mb)
Anemometer
An instrument that measures wind velocity.
Wind vane
Instrument that measures wind direction
Wind’s two principal properties
Speed and Direction
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
Why do High and Low pressure areas occur on Earth?
- Principally because the 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
High pressure is associated with…
Strongly subsiding and diverging air
Low Pressure is associated with…
Strongly converging and rising air
Isoline
A line along which there is a constant value
Isobar
An isoline connecting all points of equal atmospheric pressure.
- denotes steepness in the pressure gradient.
- lines of equal atmospheric pressure
- intervals always at 4
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.
What does Earth’s atmospheric circulation 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. A product of the pressure gradient force and the Coriolis Force
Coriolis Force
The apparent deflection of moving objects (wind, ocean currents, planes) from travelling in a straight path, in proportion to the speed of Earth’s rotation at different latitudes.
- Northern Hemisphere: to the right
- Southern Hemisphere: to the left
- maximum at poles, zero along equator
- effect of Earth’s rotation
The Extent of Surface Friction extends to about ??? and varies with ???
500m
varies with:
- surface texture
- wind speed
- time of day/year
- atmospheric conditions
Effects of Surface Friction
Decreases Wind Speed
Reduces Effect of Coriolis Force
Causes winds to move across isobars at an angle
If the Earth did not rotate…
there would be a simple wind flow from poles to the equator. A Flow caused solely by pressure gradient.
Coriolis Force
A Deflective force that makes wind travelling in a straight path appear to be deflected in relation to Earth’s rotating surface.
Why use mercury in a barometer?
Mercury is about 14 times denser than water
Aneroid Barometer
An instrument that measures air pressure without liquid.
Normal sea-level pressure
760 mm mercury
- 2 mb (millibars)
- 32 kPa (kiloPascals)
Normal sea-level air pressure
760 mm mercury
- 2 mb (millibars)
- 32 kPa (kiloPascals)
Easterly wind
winds coming from the east
Pressure Gradient Force
differences in pressure that exist across a horizontal distance
In the northern hemisphere, the Coriolis force ..
acts at 90 degrees to the right of the object in motion
in the southern hemisphere, the Coriolis force…
acts at 90 degrees to the left of the object in motion
Difference between geostrophic and surface wind
Greater frictional force and resulting slow wind speeds mean that surface winds are less affected/deflected by Coriolis force.
In high pressure systems, wind moves __ward in a ____wise motion. and wind is directed _____ward
outward, clockwise, downwards.
In low pressure systems, wind moves __ward in a ____wise motion. and is directed ____ward
inward, counterclockwise, upwards.
Hadley Cells
Circulation between 0 and 30 degrees
Ferrell Cell
Circulation between 30 and 60 degrees
Polar Cell
Circulation between 60 and 90 degrees
Land Vs Water in terms of rate of heating?
land heats up faster
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
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)
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.
Santa Ana Winds
California.
Conditions that occur in the fall and winter time. High to low pressure gradient causes a dry wind flow to the pacific ocean, funnelled through mountains. This increases speed and warmth of the air.
Warm fast dry wind. Causes fires.
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.
Monsoon
Seasonal reversal of wind
