Atmospheric and ocean circulations Flashcards
one of the most important outputs of the Earth-atmosphere energy system
global circulation of winds and ocean currents
true or false
our atmosphere is shared by all humanity
true
air pressure
the weight of the atmosphere described as force per area
air pressure is due to the
weight of the air above us
air pressure is key to understand
wind
air pressure makes _____
gradients
_____ and _____ decrease with altitude in the atmosphere
density and pressure
what affects density
water vapour in the air
moist air is ______
lighter
why is moist air lighter
the molecular weight of water is less than that of the molecules making up dry air
warm, humid air is associated with
low pressure
cold, dry air is associated with
high pressure
a ______ is used to measure atmospheric pressure
barometer
how does a barometer measure atmospheric pressure
using liquid mercury because mercury reacts to changes in pressure
an ______ barometer is used to measure pressure without liquid
aneroid
how is atmospheric pressure measured today
by electronic sensors that provide continuous measurements over time
how to compare pressure conditions from place to place
pressure measurements are adjusted and compared to a standard of normal-sea level pressure
standard atmosphere and pressure at sea level
temp = 15 degrees Celcius
pressure = 101.325 kPa
density = 1.23 kg/m3
what scales are used to measure pressure
- millibars
- inches of mercury
what is the normal range for air pressure
980 to 1050 mb
wind
the generally horizontal motion of air across earth’s surface
anemometer
measures wind speed
wind vane
determines wind direction
winds are named for the
direction from which they originate
wind is Lethbridge is often moving
westerly (west to east)
four forces that determine both the speed and direction of wind
- gravitational force
- pressure gradient force (PGF)
- Coriolis effect
- friction force
PGF
drives air from areas of higher barometric pressure to areas of lower
gradient
rate of change in some property over distance
can there be wind without a pressure gradient force
NO
does air motion have to be horizontal to create pressure gradients
NO, it can also be vertical
at higher pressure there are ____ winds
lighter
low pressure there is _____ winds
strong
why is the flow of wind a vector
it has speed and direction
thermal circulation system
occur with horizontal PG created by contrasting thermal environments
Aloft
what is above us
at a higher pressure the air is _____ (cold or warm)
cold
at a low pressure the air is _____ (cold or warm)
warm
what is used to balance the imbalance in pressure
wind to move matter
what develops in warm air
air rises which creates a low pressure at the surface
what develops in cold air
air falls and an area of high pressure develops at the surface
why would a be warmer than b
based on a different surface (one that absorbs more heat)
why is the warm pressure higher
air in A is warmer and it expands thus it rises and more air is above this pressure.
It also is less dense which means there is less to move through
how can the air pressure be equalized
by the physical transfer of matter from the high pressure to the low pressure with the development of a wind pattern
what is found at the surface of A and the surface of B
A- surface pressure falls (low pressure)
B- surface pressure rises (high pressure)
isobar
isoline plotted on a weather map that connects points of equal pressure
_____ of isobars shows intensity of the pressure difference
spacing between them
the steep gradient of isobars causes
faster air movement from high to low pressure
wider spaced isobars mark a _____ pressure change
gradual
Coriolis force
makes wind travelling in a straight path appear to be deflected in relation to earth’s rotating surface
Coriolis force is an apparent force that affects
the direction of moving objects
Coriolis force in the Northern Hemisphere
deflection is to the right according to the original motion
Coriolis force in the Southern Hemisphere
deflection is to the left according to the original motion
where is Coriolis force maximized
in areas with max rotation per unit area (more polewards)
what can Coriolis force deflect
- wind
- artillery
- airplanes
the strength of Coriolis force is proportional to
wind speed
where does the Coriolis force strengthen more
poleward
how to figure out which vector shows the most Coriolis force
the one the most poleward
(70 Latitude has more Coriolis force than 60 latitude)
Coriolis force is dependent on
latitude
Coriolis force at the equator
translational movement of the surface
what value is Coriolis force at the equator
zero
what is Coriolis force at the poles
rotational movement
where is friction found
in the boundary layer (where atmosphere and surface meet)
what does friction cause
drag as the wind moves across the surface
friction ____ with height
decreases
why does friction decrease with height
there is no friction aloft because there is nothing to impose friction
what happens to surface winds without friction
they would move parallel to isobars at high speeds
_____ air winds are NOT affected by friction forces
upper
_____ surfaces produce more friction
rougher
geostrophic winds occurs were
friction is minor (not existent)
geostrophic winds are located
above the planetary boundary layer
geostrophic winds are the balance
between PGF and Coriolis force
_____ winds are reduced by friction
surface
what type of wind has a weaker Coriolis force
surface winds
how do surface winds cross the isobars
at an angle
surface winds spirals into ___
cyclones
surface winds spiral out of _____
anticyclones
what happens if the friction force increases
the angle the wind crosses the isobar gets bigger
how do geostrophic winds cross the isobars
parallel
surface winds have a CF and PGF force _____
no longer perpendicular
surface winds are a _____ of forces
three-way balance
why do local winds have pressure differences
linked to temp differences that occur due to variations in surface or terrain
land and sea breezes are a result of
temp differences in surface properties
mountain and valley winds are a result of
temp differences in terrain
what direction is the breeze
its a sea breeze from the sea to the land
the water has a ____ temp and as such ____ pressure on surface and a ____ pressure aloft
- cold
- high pressure
- low pressure
the land has a _____ temp and as such ____ pressure on surface and a ___ pressure aloft
- warm
- low pressure
- high pressure
what direction is the breeze
its a land breeze from land to water
the water has a _____ temp and as such ____ pressure on surface and a ___ pressure aloft
- cool
- Low pressure
- High pressure
the land has a _____ temp and as such ____ pressure on surface and a ___ pressure aloft
- Cold (more cold than water)
- High pressure
- Low pressure
is this at day or night
night
is this day or night
day
air rising up a slope creates a
valley wind
what pressure is higher low or high
low
cold air falling down a slope creates
mountain wind
where is pressure higher
adjacent to the slope than over the valley