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ATPL Meteorology > Wind > Flashcards

Wind Flashcards

1
Q

How do you measure surface wind

A

Anemometer

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2
Q

How high is a anemometer placed

A

10m agl (33ft)

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3
Q

What is a gust

A

Wind increases by 10 kts for less than a minute

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4
Q

What is calm wind

A

<1knot

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5
Q

What is a gale

A

34-47kt

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6
Q

What is a storm

A

48-63 knots

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7
Q

What is a hurricane

A

> 64 kts

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8
Q

What is a squall wind

A

Gust lasting more than 1 minute

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9
Q

What is a lull

A

Sudden drop in wind speed

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10
Q

What North is used for wind direction from ATC / ARIS

A

Magnetic

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11
Q

What North is used for all meteorological reports in wind

A

True

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12
Q

When does a geostrophic wind occur

A

When pressure gradient and Coriolis force equal in strength and magnitude in opposite directions

Straight isobars

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13
Q

What is the gradient wind model

A

The same as the geostrophic wind except that it takes into account of turning air flow

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14
Q

What happens to a sea/ land breeze in the northern hemisphere

A

Deflected to the right due to Coriolis

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15
Q

What height do sea breezes affect

A

Up to around 1000ft

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16
Q

What causes adiabatic winds

A

Daytime

Side of mountain heats up due to sun

Air next to it heats up

Less dense

Rises

Upwards wind

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17
Q

What is a katabatibc wind

A

Nighttime

Opposite of adiabatic

Can cause a mountain wind which is air flowing out of a valley into an assumed plain (dependant on land)

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18
Q

What is the bora

A

A katabatic wind near Italy

Strongest in winter when air is coolest

Speeds of up to 100kts

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19
Q

What is the mistral

A

Wind flows down the Rhône valley between the alps and the mistral into the Mediterranean

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20
Q

What are the southerly winds from North Africa called

A

Sirocco
Ghibli
Khamsin

Dry dusty winds

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21
Q

What are isohypes

A

Lines of equal height set at a certain pressure

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22
Q

What is the speed of a jet stream

A

Over 60 knots

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23
Q

What do close isohypes represent

A

Likely to be jet stream

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24
Q

Where is the maximum clear air turbulence at a jet stream

A

Primary CAT = in warm air mass on the cold air side of the core, level with or just below the core

Pad pilot p312

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25
Q

Where is the secondary CAT for a jet stream

A

Above the core at the tropopause

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26
Q

What is a isotach

A

Lines of equal windspeed

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27
Q

What is the average jet steam dimensions

A

2nm deep
2000nm long
200nm wide

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28
Q

What is the depth - width ratio of a jet stream

A

1:100

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29
Q

What is the depth - length ratio of a jet stream

A

1:1000

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30
Q

What season are jet streams strongest

A

Winter

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31
Q

What causes jet streams

A

Temperature difference

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32
Q

“As climbing towards the jet stream” what happens to the wind direction

A

Veers

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33
Q

If you take off at the warm front and fly to the tropopause / jet stream what direction does the wind change

A

Veers

34
Q

If you take off st the cold front and fly towards the jet stream what way does the wind go

A

Backs

35
Q

If you’re at the surface when a front passes what happens to the wind

A

Veers

36
Q

What happens to wind speed near s trough or s ridge

A

Wind speed faster

37
Q

How fast does a jet stream need to be to appear on a sigwx chart

A

> 80 knots

38
Q

What speed is the vertical extent of a jet stream shown

A

> 120 knots

39
Q

What does a double bar at a jet stream mean

A

Speed change of more than 20 knots

Or height change of more than 3000 ft

40
Q

Where is the arctic jet stream

A

60°n

41
Q

When and what height and speed is the arctic jet stream

A

Winter only in northern hemisphere

20,000 ft (400hpa)
80 knots

42
Q

Where is the polar jet stream

A

Winter = 40-60°n > s/w Uk

Summer 70°n novascotia > Scottish islands)

43
Q

What height and speed is the polar front jet stream

A

30,000 feet (300hpa)

200knots average

Stronger in winter

Fastest jet stream

44
Q

What can clear air turbulence cause

A

Structural damage

Fatigue

45
Q

Where and when is the sun tropical jet stream

A

Winter = 20°n

Summer = 40°n

All year round

46
Q

What height and speed is the sub tropical jet stream

A

40,000feet

100knots

Stronger in winter

47
Q

Where is the equatorial jet stream (tropical easterly jet stream)

A

10-20°n

Only jet stream to go east

Around India / east Africa

When land masses have heated more than the sea below

48
Q

How High / fast is the equatorial jet stream

A

50,000 ft

70-100 knots

49
Q

What jet streams exist in the Southern Hemisphere

A

Only the sub tropical and polar jet streams

50
Q

Where do you find low level jet streams

A

Southern Germany

Kansas

51
Q

What causes low level jet streams

A

Cold air mass / warm air mass boundary

500> 5000 feet

Usually around 70 knots

52
Q

Does the temperature change in the core of a jet stream if you fly through it

A

Nope

53
Q

What clouds are associated with jet streams

A

Cirrus

54
Q

Where is the biggest temperature different founded for jet stream formation

A

Between polar and tropical air

55
Q

How deep is the friction layer

A

2/3000 ft

56
Q

What does the wind do in the friction layer over land during the day

A

Speed halves

Backs by around 30° during the day over land

57
Q

What does wind do in the friction layer over the sea

A

Slowed by 25%

Backs by 10°

58
Q

At night what happens to the height of the friction layer over land

A

Due to less thermal heating = shallowed

1/1500 feet

59
Q

At night what happens to the friction layer over land

A

Speed reduces by 75%

Wind direction backs by 45°

60
Q

What are foehn clouds

A

Where warm moist air blows on the windward side of a mountain
Rises condenses cools at a slower rate

Rain falls making the air dry

Stable so falls on other side of mountain

Becomes unsaturated sooner

Therefor warms quicker making it warmer on leeward side

61
Q

What is the foehn called over the Rocky Mountains

A

Chinook

62
Q

What is the foehn caked over the Andes

A

Santa Anna

63
Q

What are the winds at the 40°s
50°s
Called

A

Roaring 40s
Furious 50s

Very fast westerly winds

64
Q

What is a equatorial doldrums

A

Very light wind at itcz

65
Q

What are the North easterly winds over North Africa called

A

Harmattan

Bad vis

66
Q

What is the pampero

A

Local winds of South America burst of cold polar air from south west in South America

Strongest every summer
Associated with cold front

Happens in s Australia

67
Q

After what height does the turbulence criteria include in transport aircraft

A

> 15,000 feet

68
Q

What is light turbulence

A

Bit bumpy but not much
May feel flight strain on seatbelts
Can still walk / serve food
5-15kt fluctuations in IAS

If no airspeed change = light chop

69
Q

What is moderate turbulence

A 
Bumps jolts 
Positive control of aircraft at all times
15-25knot speed fluctuations 
Definite strain on seatbelts 
Insecure objects dislodged 
Struggle to walk / serve food
70
Q

What is severe turbulence

A

Momentary loss of control
IAS fluctuations 25>
Food / walking impossible
Insecure objects tossed about

71
Q

When should you report turbulence

A

If not already been reported moderate / severe and above 15,000ft

72
Q

What is occasional turbulence

A

Less than 1/3 of the time

73
Q

What is intermittent turbulence

A

1/3 > 2/3 of the time

74
Q

What is continuous turbulence

A

More than 2/3 of the time

75
Q

What causes mountain waves

A

Wind flowing >15 knots at top of mountain

90° (+/-30) to mountain

Layer of stable air on top of mountain with less stable air above and below

76
Q

What area causes the greatest danger in mountain waves

A

Rotor zone

77
Q

How far can mountain waves affect after mountain s

A

50-100nm

78
Q

How fast can the up/down draughs be for mountain waves

A

1000feet/min

79
Q

What is the scale for wondshear

A

Horizontal = knots / 1000ft

Vertical = knots / 100ft

80
Q

Where can wind shear occur

A

At top of inversions
In micro bursts
CB/TS
frontal passage

ATPL Meteorology (8 decks)

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