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ppl course - (3) navigation and meteorology > Chapter 8.4 - Pressure Systems and Wind > Flashcards

Chapter 8.4 - Pressure Systems and Wind Flashcards

1
Q

What number appears on the Isobars?

A

MSL Pressure (hPa).

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2
Q

What is a region of High Pressure called and it’s marking on synoptic charts (2)?

A
  • Anticyclone.

- H or High.

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3
Q

What is a region of Low Pressure called and it’s marking on synoptic charts (2)?

A
  • Cyclone/Depression.

- L or Low.

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4
Q

An elongated region of High Pressure extending outwards from an Anticyclone is called?

A

Ridge.

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5
Q

An elongated region of Low Pressure extending outwards from a Cyclone is called?

A

Trough.

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6
Q

In an Anticyclone, the central pressure is ‘x’ than the surrounding area?

A

Greater.

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7
Q

In which directions does airflow in High Pressure?

A

Anticlockwise.

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8
Q

Which inversion is associated with High Pressure?

A

Subsidence.

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9
Q

Which type of clouds (if any) form under High Pressure?

A

Stratiform

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10
Q

In a Cyclone, the central pressure is ‘x’ than the surrounding area?

A

Lower.

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11
Q

In which directions does airflow in Low Pressure?

A

Clockwise.

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12
Q

A Cyclone in the tropics is known as?

A

Tropical Depression.

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13
Q

A Tropical Cyclone is when the central pressure has fallen below ‘x’ hPa and the windspeed has increased to above ‘x’ knots?

A
  • 1000 hPa.

- 34 kts.

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14
Q

Which type of clouds form under Low Pressure?

A

Cumuliform.

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15
Q

An area of Neutral Pressure between two Anticyclones and Cyclones is called?

A

Col.

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16
Q

Name three types of Col?

A
  • Anticyclonic Col.
  • Cyclonic Col.
  • Neutral Col.
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17
Q

True or False. A Col will appear on the weather map with Isobars?

A

False.

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18
Q

Air in horizontal/vertical motion is called wind?

A

Horizontal.

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19
Q

Define Pressure Gradient Force?

A

The resulting force when there is a difference in pressure across a surface.

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20
Q

True or False. The steeper the pressure gradient, the larger the pressure gradient force?

A

True.

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21
Q

Wind tends to blow at right angles to/parallel to Isobars?

A

Parallel.

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22
Q

The spacing of Isobars indicate the size of what?

A

Pressure Gradient.

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23
Q

Describe the wind between Isobars being closer and further apart from each other (2)?

A
  • Closer = Stronger Winds.

- Further = Lighter Winds.

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24
Q

Describe the pressure between Isobars being closer and further apart from each other (2)?

A
  • Closer = Rapid changes in Pressure.

- Further = Slower changes in Pressure.

25
Q

Wind is described (in maps, charts, ATC and ATIS) as coming from or going to?

A

Coming from.

26
Q

Meteorologists will give wind direction from True North/Magnetic North?

A

True North.

27
Q

ATC and ATIS will give wind direction from True North/Magnetic North?

A

Magnetic North.

28
Q

Define Gradient Wind and its movement around Isobars (2)?

A
  • The wind resulting in the combined forces of Pressure, Coriolis and Centripetal.
  • Parallel to.
29
Q

True or False. Isobars on a surface synoptic chart will indicate the direction and speed of the gradient wind?

A

True.

30
Q

True or False. Latitude doesn’t have any effect on Isobars?

A

False.

31
Q

Define Friction Layer?

A

The layer adjacent to the earth’s surface.

32
Q

Define Surface Wind?

A

The result of surface friction changing/modifying the gradient wind.

33
Q

The speed of the surface wind varies the gradient wind by how much percentage over the ocean?

A

60% to 75%.

34
Q

The speed of the surface wind varies the gradient wind by how much percentage over land areas?

A

30% to 50%.

35
Q

True or False. The friction layer affects the direction of surface wind?

A

True.

36
Q

When will Pilots need to know the surface wind?

A

Takeoff and Landing.

37
Q

In the southern hemisphere, the wind will always change in which direction?

A

Clockwise.

38
Q

Define Gusts?

A

An increase in windspeed over the mean, lasting for more than a few seconds.

39
Q

Define Lulls?

A

A decrease in windspeed below the mean, lasting for more than a few seconds.

40
Q

Define Squall?

A

A sudden increase in windspeed lasting for a few minutes and then dissipating.

41
Q

Define Gale?

A

Windspeed of 34 kt or more.

42
Q

Define Veering?

A

Wind direction changes clockwise.

43
Q

Define Backing?

A

Wind direction changes anticlockwise.

44
Q

What is the average wind speed (kt) in the Wind Category Calm?

A

Less than 1.

45
Q

What is the average wind speed (kt) in the Wind Category Light?

A

1 to 10.

46
Q

What is the average wind speed (kt) in the Wind Category Moderate?

A

11 to 21.

47
Q

What is the average wind speed (kt) in the Wind Category Strong?

A

22 to 33.

48
Q

What is the average wind speed (kt) in the Wind Category Gale?

A

34 to 40.

49
Q

Name one main cause of local winds?

A

The density difference between the air over areas of the earth’s surface.

50
Q

What is a Sea Breeze?

A

A local wind occurring in coastal areas moving to land.

51
Q

How are Sea Breezes caused?

A

Differential heating of the air above the land and sea.

52
Q

Which times will a Sea Breeze start and will be at its strongest (2)?

A
  • Weak = 0900 LMT.

- Strong = 1500 or 1600 LMT.

53
Q

A Sea Breeze can last for a distance between?

A

8 to 16 kilometres inland.

54
Q

What is a Land Breeze?

A

A local wind occurring over land moving to sea.

55
Q

Which times will a Sea Breeze start and will be at its strongest (2)?

A
  • Midnight.

- Just after sunrise.

56
Q

A Land Breeze can last for a distance between?

A

5 to 8 kilometres out to sea.

57
Q

What is Foehn Wind?

A

Warm and dry wind flowing down the lee side of a mountain.

58
Q

Both Foehn and Karabatic winds produce which type of currents from high ground?

A

Down currents.

ppl course - (3) navigation and meteorology (23 decks)

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