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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 ….

A

Poles

24
Q

As the air cools….

What happens in the subtropical region?

A

It descends in the subtropical regions

25
Q

Subsiding air forms a belt of high pressure known as…

A

Subtropical ridge

26
Q

What is the polar high?

A

Over the poles cold dense air results in a region of high pressure

27
Q

What is the sub-polar low?

A

As converging air meets it is forced upwards, this forms a low pressure belt

28
Q

What generates the world’s major airstreams?

A

Movement of air near the surface from the high-pressure belts towards the low-pressure regions

29
Q

In the southern hemisphere, Coriolis deflects moving air …

A

Left

30
Q

Why do we experience seasons?

A

Due to the tilt of the Earths axis

31
Q

Does the equatorial trough remain stationary over the equator all year round?

A

No

32
Q

In summer in the southern hemisphere what happens to the Equatorial trough?

A

It moves south to lie across Northern Australia

33
Q

What is the North West Monsoon?

A

Air flowing towards the equatorial trough crosses the equator and is deflected left due to Coriolis force

34
Q

In winter over northern Australia winds are southeasterly due to..

A

The influence of the southeast trades. Resulting in dry conditions over northern Australia except the east coast

35
Q

The Southeast trade winds blow from the subtropical ridge towards…

A

The equatorial trough

36
Q

Due to continual large-scale subsidence over the subtropical ridge, a widespread inversion exists extending towards…

A

The Equatorial trough

37
Q

What are the roaring ’40s?

A

The roaring ’40s prevail around 40 degrees S latitude as air flows from the subtropical ridge towards subpolar low

38
Q

In relation to the roaring ’40s;

The direction is northwesterly in the southern hemisphere due to….

A

Coriolis deflection

39
Q

What do local pressure patterns have a strong influence on?

A

Wind Velocity

40
Q

What does wind direction depend on?

A

Relative strength of the gradient force and Coriolis effect

41
Q

Gradient wind flows parallel to…

A

Curved Isobars when coriolis force matches the gradient force

42
Q

Geostrophic flow is parallel to …

A

Straight Isobars when the forces are matched

43
Q

What is the lower 3000ft of the atmosphere known as?

A

Friction Layer

44
Q

In the friction layer wind speed is…

A

reduced

Due to the friction with the surface

45
Q

Over the land wind speed is reduced by…

A

2/3rds

46
Q

Over the Sea wind speed is reduced by…

A

1/3rd

47
Q

Reduction in wind speed reduces Coriolis; reduced Coriolis causes

A

Wind in the friction layer to veer compared to wind aloft

48
Q

Above the friction layer, layer wind tends to flow….

A

Parallel to isobars (Gradient wind)

49
Q

At the surface the wind veers to flow cross isobars towards what?

A

Low pressure

50
Q

Surface wind veers across isobars at what degrees?

A

30 degrees over land

10 degrees over water

51
Q

Why at the equator does wind flow perpendicular to the isobars?

A

Lack of Coriolis deflection

52
Q

During the day does land or sea heat faster?

A

Land

53
Q

Rising air over the land draws in cooler air from the sea; at the surface this is called?

A

Sea Breeze

54
Q

At night the sea is warmer due to what?

A

Specific heat

55
Q

What is land breeze?

A

The opposite of sea breeze, cool air from the land flows to the sea

56
Q

What is katabatic wind?

A

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
Q

What are Anabatic winds?

A

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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