ATOC 1050 EXAM 2: CHECK YOUR
UNDERSTANDING
Which 4 forces control the movement of air? - ANSWER-Pressure Gradient Force
Frictional Force
Gravitational Force
Coriolis Force
What causes the pressure gradient force? - ANSWER-exists anywhere pressure
changes with distance
In what direction does the pressure gradient force act? - ANSWER-high pressure → low
pressure
What causes friction in moving air? - ANSWER-occurs when faster moving molecules
collide with slower moving molecules or the earth's surface
In which direction does friction act? - ANSWER-opposite the direction of air motion
What is the Coriolis force? - ANSWER-an apparent force associated with the rotation of
the Earth
In what direction does the Coriolis force act in the Northern Hemisphere? - ANSWER-
acts on objects in motion across the Earth's surface and acts to the right of the direction
of motion in the northern hemisphere
What is geostrophic balance? - ANSWER-The force balance that exists when the
horizontal pressure gradient force is equal and opposite to the Coriolis force
What is hydrostatic balance? - ANSWER-The force balance that exists when the vertical
pressure gradient force is equal and opposite to the gravitational force
What is the jetstream? - ANSWER-The band of strong winds that circles the globe in
middle latitudes just below the tropopause
It's horizontal position is associated with strong horizontal surface temperature gradients
in the troposphere
Between what altitudes is the jetstream typically found? - ANSWER-around 300mb, but
can be as low as 500mb
How is the pressure gradient force related to the wind speed? - ANSWER-In the
absence of other forces, the pressure gradient force is proportional to wind
, speed
What does a strong pressure gradient look like on a sea-level pressure map? -
ANSWER-The pressure gradient force is strong where isobars are close together and
weak where there are far apart.
Given that the vertical pressure gradient force acts upward, why don't air molecules fly
off into space? - ANSWER-Gravity acts to hold air on the earth, balancing the upward
pressure gradient force.
Mechanical Turbulence - ANSWER-Mechanical turbulence develops when air collides
with ground object
Thermal Turbulence - ANSWER-Thermal turbulence develops when warm plumes of air
rise and mix with air above
Shear-induced Turbulence - ANSWER-Shear-induced turbulence develops when wind
speed changes with distance (typically with height) and the faster moving air mixes with
the slower moving air
On a hot summer day, air flows off the southeast coast of the United States and over
the Atlantic Ocean. What should happen to the depth of the friction layer once the air
moves over the ocean? - ANSWER-The depth of the friction layer will decrease, since
mechanical turbulence is reduced because the water is smooth compared to the land
surface.
What is a typical depth of the friction layer in the atmosphere? - ANSWER-The friction
layer varies in depth. On a night with weak winds, the boundary layer over a large lake
may only extend upward a few hundred meters, while the boundary layer over a city on
a hot, windy afternoon may extend upward a few thousand meters.
Which direction does the Coriolis Force cause object to deviate in the northern
hemisphere? Southern Hemisphere? - ANSWER-The Coriolis force causes objects to
deviate to the right of their direction of motion in the Northern Hemisphere and to the left
in the Southern Hemisphere)
Does the Coriolis Force affect an object's speed? - ANSWER-affects the direction an
object will move across the earth's surface, but has no effect on its speed
When is the Coriolis Force strongest? - ANSWER-Strongest for fast-moving objects
When is the Coriolis Force zero? - ANSWER-Zero for stationary objects
Zero at the equator
When is the Coriolis Force maximum? - ANSWER-At the poles
UNDERSTANDING
Which 4 forces control the movement of air? - ANSWER-Pressure Gradient Force
Frictional Force
Gravitational Force
Coriolis Force
What causes the pressure gradient force? - ANSWER-exists anywhere pressure
changes with distance
In what direction does the pressure gradient force act? - ANSWER-high pressure → low
pressure
What causes friction in moving air? - ANSWER-occurs when faster moving molecules
collide with slower moving molecules or the earth's surface
In which direction does friction act? - ANSWER-opposite the direction of air motion
What is the Coriolis force? - ANSWER-an apparent force associated with the rotation of
the Earth
In what direction does the Coriolis force act in the Northern Hemisphere? - ANSWER-
acts on objects in motion across the Earth's surface and acts to the right of the direction
of motion in the northern hemisphere
What is geostrophic balance? - ANSWER-The force balance that exists when the
horizontal pressure gradient force is equal and opposite to the Coriolis force
What is hydrostatic balance? - ANSWER-The force balance that exists when the vertical
pressure gradient force is equal and opposite to the gravitational force
What is the jetstream? - ANSWER-The band of strong winds that circles the globe in
middle latitudes just below the tropopause
It's horizontal position is associated with strong horizontal surface temperature gradients
in the troposphere
Between what altitudes is the jetstream typically found? - ANSWER-around 300mb, but
can be as low as 500mb
How is the pressure gradient force related to the wind speed? - ANSWER-In the
absence of other forces, the pressure gradient force is proportional to wind
, speed
What does a strong pressure gradient look like on a sea-level pressure map? -
ANSWER-The pressure gradient force is strong where isobars are close together and
weak where there are far apart.
Given that the vertical pressure gradient force acts upward, why don't air molecules fly
off into space? - ANSWER-Gravity acts to hold air on the earth, balancing the upward
pressure gradient force.
Mechanical Turbulence - ANSWER-Mechanical turbulence develops when air collides
with ground object
Thermal Turbulence - ANSWER-Thermal turbulence develops when warm plumes of air
rise and mix with air above
Shear-induced Turbulence - ANSWER-Shear-induced turbulence develops when wind
speed changes with distance (typically with height) and the faster moving air mixes with
the slower moving air
On a hot summer day, air flows off the southeast coast of the United States and over
the Atlantic Ocean. What should happen to the depth of the friction layer once the air
moves over the ocean? - ANSWER-The depth of the friction layer will decrease, since
mechanical turbulence is reduced because the water is smooth compared to the land
surface.
What is a typical depth of the friction layer in the atmosphere? - ANSWER-The friction
layer varies in depth. On a night with weak winds, the boundary layer over a large lake
may only extend upward a few hundred meters, while the boundary layer over a city on
a hot, windy afternoon may extend upward a few thousand meters.
Which direction does the Coriolis Force cause object to deviate in the northern
hemisphere? Southern Hemisphere? - ANSWER-The Coriolis force causes objects to
deviate to the right of their direction of motion in the Northern Hemisphere and to the left
in the Southern Hemisphere)
Does the Coriolis Force affect an object's speed? - ANSWER-affects the direction an
object will move across the earth's surface, but has no effect on its speed
When is the Coriolis Force strongest? - ANSWER-Strongest for fast-moving objects
When is the Coriolis Force zero? - ANSWER-Zero for stationary objects
Zero at the equator
When is the Coriolis Force maximum? - ANSWER-At the poles
