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ATPL Meteorology > Wind > Flashcards

Wind Flashcards

1
Q

What is Wind?

A

Air in motion over the earths surface

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2
Q

Wind Velocity is a … quantity

A

Vector

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3
Q

What is a vector expressed as?

A

Magnitude and Direction

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4
Q

The wind magnitude is its speed in

A

Knots

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5
Q

Direction of wind refers to?

A

The direction FROM which the wind is blowing, expressed in degrees relative to North

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6
Q

Wind velocity is measured at

A

10 meters over open level terrain for 10 minutes

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7
Q

What is a gust?

A

Sudden increase in wind speed lasting a short time and dying suddenly

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8
Q

What is a squall?

A

Sudden increase in wind speed by at least 16kts or more, lasting at least one minute and reaching top speeds of 22kts

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9
Q

What is a veer?

A

Wind direction changes in clockwise manner

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10
Q

What is a back?

A

Wind direction changes in an anticlockwise manner

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11
Q

What is pressure gradient force?

A

Causes air to tend to flow from high to low pressure across isobars

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12
Q

What does the strength of pressure gradient depend on?

A

Spacing of isobars and is measured perpendicular to isobars

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13
Q

What is Coriolis effect?

A

Due to earths rotation, moving air is deflected to the left in the southern hemisphere

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14
Q

Where is Coriolis effect zero?

A

Equator

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15
Q

Where is Coriolis effect maximum?

A

Poles

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16
Q

What does the strength of Coriolis depend on?

A

Wind Speed

  • The stronger the wind, the stronger the deflection
  • The relative strength of these forces governs wind direction
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17
Q

Buys Ballots Law

A

With your back to the wind the lower pressure system will be on your right (in the southern hemisphere)

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18
Q

The overall pattern of air circulation around the globe results from…

A

The distribution of pressure systems

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19
Q

Pressure systems are formed by…

A

Uneven heating of the earths surface

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20
Q

Why is there a large scale convection over the equator?

A

Air in contact with the earths surface at the equator is warmed and rises

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21
Q

What is the equatorial trough?

A

The rising air generates a low pressure system

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22
Q

What is the equatorial trough also called?

A

Inter-tropic convergence zone or the doldrums

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23
Q

At higher levels the air begins to move horizontally towards the ….

24
Q

As the air cools….

What happens in the subtropical region?

A

It descends in the subtropical regions

25
Subsiding air forms a belt of high pressure known as...
Subtropical ridge
26
What is the polar high?
Over the poles cold dense air results in a region of high pressure
27
What is the sub-polar low?
As converging air meets it is forced upwards, this forms a low pressure belt
28
What generates the world's major airstreams?
Movement of air near the surface from the high-pressure belts towards the low-pressure regions
29
In the southern hemisphere, Coriolis deflects moving air ...
Left
30
Why do we experience seasons?
Due to the tilt of the Earths axis
31
Does the equatorial trough remain stationary over the equator all year round?
No
32
In summer in the southern hemisphere what happens to the Equatorial trough?
It moves south to lie across Northern Australia
33
What is the North West Monsoon?
Air flowing towards the equatorial trough crosses the equator and is deflected left due to Coriolis force
34
In winter over northern Australia winds are southeasterly due to..
The influence of the southeast trades. Resulting in dry conditions over northern Australia except the east coast
35
The Southeast trade winds blow from the subtropical ridge towards...
The equatorial trough
36
Due to continual large-scale subsidence over the subtropical ridge, a widespread inversion exists extending towards...
The Equatorial trough
37
What are the roaring '40s?
The roaring '40s prevail around 40 degrees S latitude as air flows from the subtropical ridge towards subpolar low
38
In relation to the roaring '40s; | The direction is northwesterly in the southern hemisphere due to....
Coriolis deflection
39
What do local pressure patterns have a strong influence on?
Wind Velocity
40
What does wind direction depend on?
Relative strength of the gradient force and Coriolis effect
41
Gradient wind flows parallel to...
Curved Isobars when coriolis force matches the gradient force
42
Geostrophic flow is parallel to ...
Straight Isobars when the forces are matched
43
What is the lower 3000ft of the atmosphere known as?
Friction Layer
44
In the friction layer wind speed is...
reduced | Due to the friction with the surface
45
Over the land wind speed is reduced by...
2/3rds
46
Over the Sea wind speed is reduced by...
1/3rd
47
Reduction in wind speed reduces Coriolis; reduced Coriolis causes
Wind in the friction layer to veer compared to wind aloft
48
Above the friction layer, layer wind tends to flow....
Parallel to isobars (Gradient wind)
49
At the surface the wind veers to flow cross isobars towards what?
Low pressure
50
Surface wind veers across isobars at what degrees?
30 degrees over land | 10 degrees over water
51
Why at the equator does wind flow perpendicular to the isobars?
Lack of Coriolis deflection
52
During the day does land or sea heat faster?
Land
53
Rising air over the land draws in cooler air from the sea; at the surface this is called?
Sea Breeze
54
At night the sea is warmer due to what?
Specific heat
55
What is land breeze?
The opposite of sea breeze, cool air from the land flows to the sea
56
What is katabatic wind?
With clear night skies; air in contact with a mountain side may be cooled by conduction, increased density causes the air to flow down the mountain generating katabatic winds
57
What are Anabatic winds?
During the day; air in contact with a mountain side may heat due to conduction, reduced density causes the air to rise, flowing upslope.

ATPL Meteorology (12 decks)

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