Chapter 6 Flashcards

1
Q

Wind

A

air in motion that arises from a combination of forces

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2
Q

Wind speed is reported on U.S. weather maps in ____________

A

knots

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3
Q

Knots

A

One nautical mile per hour (equivalent to about 1.15 miles per hour, or 0.5 meters per second

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4
Q

If the wind speed is strong (greater than 15 knots) and highly variable, the weather report will include the __________

A

wind gust - the maximum observed wind speed

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5
Q

Wind direction

A

The direction from which the wind is blowing

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6
Q

Cyclones

A

Low-pressure centers

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7
Q

anticyclones

A

high-pressure systems

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8
Q

velocity

A

the magnitude and direction of its motion

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9
Q

speed

A

the distance traveled in a given amount of time

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10
Q

acceleration

A

a change in an object’s velocity - magnitude, direction, or both

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11
Q

Forces are characterized by:

A

direction and magnitude (or strength)

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12
Q

Net force or Resultant

A

The overall force that results from interacting forces can be expressed as a single force

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13
Q

Newton’s Second Law of Motion

A

A force exerted on an object (or a parcel of air) of a given mass causes the object to accelerate in the direction of the applied force

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14
Q

Force =

A

Mass x Acceleration

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15
Q

Acceleration =

A

Force / mass

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16
Q

5 different forces combine to move air:

A

the gravitational force, the pressure gradient force (PGF), the centrifugal force, the Coriolis force, and the frictional force

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17
Q

Gravitational force (GF)

A

Directed downward perpendicular to the ground and is approximately equal to the mass times the gravitational acceleration, 9.8 meters per second per second

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18
Q

pressure gradient

A

A change in presure over a distance

19
Q

PGF always pushes from

A

higher pressure toward lower pressure

20
Q

PGF =

A

(- 1 / Air density) x (change in pressure / distance)

21
Q

When pressure changes rapidly over a small distance =>

A

PGF is large

22
Q

The PGF always pushes directly from

A

higher pressure toward lower pressure

23
Q

Isobaric maps are useful for portraying:

A

horizontal pressure gradients above the ground

24
Q

The steeper the slope of the pressure surfaces =>

A

the greater the PGF because the pressure gradient is the change in pressure over distance

25
Centripetal acceleration
When an object changes its direction of motion, it is accelerating even if its speed does not change
26
CENTF =
V^2 / R V = wind speed R = radius of curvature of the curved path
27
The faster the speed and the tighter the curve of the path traveled (smaller R), the larger is the
centripetal acceleration
28
Coriolis force
Characteried by a turning or deflection of the direction of moving air
29
The Coriolis force deflects movement to +\>
the right in the Northern Hemisphere to the left in the Southern Hemisphere
30
Frictional force is caused by:
The flow of wind over the roughness of the Earth's surface
31
What determine the magnitude of frictional force
The roughness of the surface and the speed of the wind
32
Sum of Forces =
Mass x Acceleration
33
When the vertical pressure gradient is equal to coriolis force (gravity) and push in opposite directions =\>
hydrostatic balance exists
34
When the PGF is counterbalanced by the Coriolis force =\>
geostrophic balance
35
Because the Coriolis force always pushes to the right of the wind in the Northern Hemisphere, this requries a wind in geostrophic balance =\>
geostrophic wind
36
Buys Ballot's Law
The "low pressure lies to the left of the wind" rule
37
Because air moves with low pressure on its left in the Northern Hemisphere =\>
the wind must blow clockwise around highs and counterclockwise around lows
38
Winds on a weather map are strong where:
isobars or isoheights are close together
39
Winds on a weather map are weak where:
isobars or isoheights are far apart
40
Gradient balance
The three-way balance of horizontal pressure gradient, Coriolis force, and centrifugal force
41
The wind that results from gradient balance is called =\>
gradient wind
42
Supergeostrophic flow
The wind speed, to which the Coriolis force is proportional - must be considerably higher than in the purely geostrophic case
43
For high and low pressure areas that have the same spacing of isobars or isoheights,, winds in gradient balance around a high will be:
stronger than winds around a low
44