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Meteorology > The Wind > Flashcards

The Wind Flashcards

1
Q

Under what conditions are gusts reported by an ATC?

A

Change of speed is not less than 10kt when compared to the mean wind speed

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2
Q

What is an indication of a large pressure gradient?

A

Closely spaced isobars and strong wind

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3
Q

You fly with left drift in the NH, how does the surface pressure change then?

A

The surface pressure increases

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4
Q

Which forces need to be balanced for the geostrophic wind to occur?

A

Pressure gradient force (PGF) and Coriolis force (CF)

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5
Q

Due to the Coriolis Force (CF), the wind…

A

Veers in the NH, and backs in the SH

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6
Q

An anemometer can be used to measure…

A

Wind speed

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7
Q

What is the expected direction and speed of wind 2000ft above LHR, if surface wind is 190°/20kts?

A

220°/40kts

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8
Q

Natural tendency of the air is that it flows

A

From high pressure to low pressure

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9
Q

The main reason for the occurrence of the wind is…

A

Pressure gradient force (PGF)

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10
Q

Minimum speed for the wind to be classed as a hurricane

A

63kts

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11
Q

Where should an anemometer be placed? (Measures surface wind)

A

10m above the level of an aerodrome

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12
Q

In high-pressure systems, when is the wind strongest?

A

The wind tends to be strongest in the early afternoons.

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13
Q

The greater the horizontal pressure gradient, the… (isobars and wind are)

A

Closer the isobars are to each other, and the stronger the wind

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14
Q

Anti-clockwise wind direction is also known as

A

Backing

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15
Q

When the wind is on your back (NH), the pressure…

A

The surface pressure decreases

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16
Q

30 m/S in kt

A

60 kts

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17
Q

Is the wind at 40°N, 50°N or 60°N strongest?

A

The wind blowing at the latitude 40°N is the strongest

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18
Q

The same Pressure gradient force (PGF) will cause stronger wind

A

At lower latitudes

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19
Q

What is the difference between gradient winds and geostrophic winds?

A

Shape of isobars

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20
Q

The greater the horizontal pressure gradient, the (isobars and wind)

A

Closer the isobars to each other and the stronger the wind

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21
Q

Name the wind that blows as a result of air warming on the slope of a mountain

A

Anabatic wind

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22
Q

Diurnal variations of temperature result in the arise of

A

Sea and land breezes

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23
Q

Where do trade winds blow from

A

Subtropical anticyclones towards the equator

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24
Q

Conditions most favourable to the formation of mountain waves

A

The wind of 30kts blowing within 20° of the perpendicular to the ridge

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25
Q

What is the Hadley cell?

A

A cell formed by the air ascending over the thermal equator and descending above the subtropical area

26
Q

Most frequent direction of the wind blowing along the slopes of a mountain during the day

A

Up the slopes

27
Q

What is the katabatic wind?

A

A flow of cold air down the slopes of a mountain

28
Q

Regions of severe turbulence appearing below mountain waves, directly beneath their crests are called?

A

Rotors

29
Q

What is the horizontal extension of sea breezes blowing at temperature latitudes?

A

Between 15 km (8NM) and 25 km (14 NM) on both sides of the coastline

30
Q

Wha is the sea breeze?

A

Wind blowing from sea to land during the day

31
Q

Name of the wind that blows as a result of air warming on the slope of a mountain?

A

Anabatic wind

32
Q

Typical distances between the core of a polar front jet stream and the surface positions of the associated fronts?

A

Around 200NM behind the cold front and about 400NM ahead of the warm front

33
Q

In the NH, crossing a jet stream. The pilot notices the OAT is increasing. Therefore, the prevailing wind…

A

Blows from the right

34
Q

What is true about mechanical turbulence?

A

Mechanical turbulence is caused by physical obstructions like buildings, trees and any irregularities of the terrain.

35
Q

What is the main reason for the formation of a polar front jet stream?

A

The strong temperature contrast between the cold polar and warm tropical air

36
Q

At what pressure levels, is the core of the Arctic jet stream found?

A

Between 400 hPa and 300 hPa

37
Q

What is the main reason for the formation of a polar front jet stream?

A

The strong temperature contrast between the cold polar and warm tropical air

38
Q

What is true about the speed of a polar front jet stream core?

A

The speed of a polar front jet stream core is greater in winter than in summer

39
Q

Which phenomenon is often associated with jet streams?

A

CAT

40
Q

In the NH, a polar front jet stream blows…

A

Between latitudes of 40°N and 60°N

41
Q

Which set of conditions are most favourable to the formation of turbulence?

A

Unstable air and rough ground

42
Q

When is the thermal turbulence most pronounced?

A

During sunny days in the early afternoon

43
Q

What is the main difference between the equatorial jet stream and every other jet stream?

A

Wind direction

44
Q

Over some location in the NH, a polar front jet stream blows from N to S. Therefore,

A

The polar air is BELOW and EASTWARDS to the core of a jet stream

45
Q

According to Buys Ballots law, when standing in the NH with our back to the wind, the cooler air mass…

A

Is on the left. low pressure is on the left

46
Q

When flying from Bangkok to Mumbai at 34,000ft in August, the wind conditions are we experience are…

A

Tailwinds

47
Q

What is the minimum speed for the wind to be classified as a jet stream?

A

60kts

48
Q

Example of a föhn wind

A

Chinook

49
Q

Where are both easterly and westerly jet streams found?

A

NH only

50
Q

Large pressure gradients are shown by…

A

Isobars close together, strong winds

51
Q

Land breeze is

A

From land over water at night

52
Q

When heading South in the SH you experience starboard drift…(temperature)

A

You are flying away from low temperature

53
Q

What prevents air from flowing directly from a high to a low pressure?

A

Coriolis force

54
Q

What causes wind at low levels?

A

Difference in oressure

55
Q

Föhn winds are…

A

Cold katabatic

56
Q

What is the difference between gradient and geostrophic winds?

A

Curved isobars and straight isobars

57
Q

Wind is caused by…

A

Horizontal pressure gradient

58
Q

What is the Bora?

A

Cold katabatic wind over the Adriatic

59
Q

What causes the geostrophic wind to be stronger than the gradient wind around a low?

A

Centrifugal force opposes the gradient force

60
Q

Standing in the NH, north of a polar frontal depression travelling west to east, the wind will….

A

Continually back

61
Q

If you fly with left drift in the NH, what is happening to the surface pressure?

A

Increases

62
Q

In Central Europe, where are the greatest wind speeds?

A

Tropopause level

Meteorology (3 decks)

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