Chapter 8.4 - Pressure Systems and Wind

Question 1

What number appears on the Isobars?

Answer 1

MSL Pressure (hPa).

Question 2

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

Answer 2

• Anticyclone.

- H or High.

Question 3

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

Answer 3

• Cyclone/Depression.

- L or Low.

Question 4

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

Answer 4

Ridge.

Question 5

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

Answer 5

Trough.

Question 6

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

Answer 6

Greater.

Question 7

In which directions does airflow in High Pressure?

Answer 7

Anticlockwise.

Question 8

Which inversion is associated with High Pressure?

Answer 8

Subsidence.

Question 9

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

Answer 9

Stratiform

Question 10

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

Answer 10

Lower.

Question 11

In which directions does airflow in Low Pressure?

Answer 11

Clockwise.

Question 12

A Cyclone in the tropics is known as?

Answer 12

Tropical Depression.

Question 13

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

Answer 13

• 1000 hPa.

- 34 kts.

Question 14

Which type of clouds form under Low Pressure?

Answer 14

Cumuliform.

Question 15

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

Answer 15

Col.

Question 16

Name three types of Col?

Answer 16

• Anticyclonic Col.
• Cyclonic Col.
• Neutral Col.

Question 17

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

Answer 17

False.

Question 18

Air in horizontal/vertical motion is called wind?

Answer 18

Horizontal.

Question 19

Define Pressure Gradient Force?

Answer 19

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

Question 20

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

Answer 20

True.

Question 21

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

Answer 21

Parallel.

Question 22

The spacing of Isobars indicate the size of what?

Answer 22

Pressure Gradient.

Question 23

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

Answer 23

• Closer = Stronger Winds.

- Further = Lighter Winds.

Question 24

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

Answer 24

• Closer = Rapid changes in Pressure.

- Further = Slower changes in Pressure.

Question 25

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

Answer 25

Coming from.

Question 26

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

Answer 26

True North.

Question 27

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

Answer 27

Magnetic North.

Question 28

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

Answer 28

- The wind resulting in the combined forces of Pressure, Coriolis and Centripetal. - Parallel to.

Question 29

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

Answer 29

True.

Question 30

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

Answer 30

False.

Question 31

Define Friction Layer?

Answer 31

The layer adjacent to the earth’s surface.

Question 32

Define Surface Wind?

Answer 32

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

Question 33

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

Answer 33

60% to 75%.

Question 34

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

Answer 34

30% to 50%.

Question 35

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

Answer 35

True.

Question 36

When will Pilots need to know the surface wind?

Answer 36

Takeoff and Landing.

Question 37

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

Answer 37

Clockwise.

Question 38

Define Gusts?

Answer 38

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

Question 39

Define Lulls?

Answer 39

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

Question 40

Define Squall?

Answer 40

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

Question 41

Define Gale?

Answer 41

Windspeed of 34 kt or more.

Question 42

Define Veering?

Answer 42

Wind direction changes clockwise.

Question 43

Define Backing?

Answer 43

Wind direction changes anticlockwise.

Question 44

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

Answer 44

Less than 1.

Question 45

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

Answer 45

1 to 10.

Question 46

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

Answer 46

11 to 21.

Question 47

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

Answer 47

22 to 33.

Question 48

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

Answer 48

34 to 40.

Question 49

Name one main cause of local winds?

Answer 49

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

Question 50

What is a Sea Breeze?

Answer 50

A local wind occurring in coastal areas moving to land.

Question 51

How are Sea Breezes caused?

Answer 51

Differential heating of the air above the land and sea.

Question 52

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

Answer 52

- Weak = 0900 LMT. | - Strong = 1500 or 1600 LMT.

Question 53

A Sea Breeze can last for a distance between?

Answer 53

8 to 16 kilometres inland.

Question 54

What is a Land Breeze?

Answer 54

A local wind occurring over land moving to sea.

Question 55

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

Answer 55

- Midnight. | - Just after sunrise.

Question 56

A Land Breeze can last for a distance between?

Answer 56

5 to 8 kilometres out to sea.

Question 57

What is Foehn Wind?

Answer 57

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

Question 58

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

Answer 58

Down currents.