Turbulence

Question 1

What are the causes of turbulence?

Answer 1

• Convective (or thermal currents)
• Mechanical turbulence
• Wind shear
• Wake turbulence

Question 2

What is turbulence?

Answer 2

Irregular motion of air from eddies or vertical currents; associated with cumuliform clouds and unstable air

Question 3

What is convective currents?

Answer 3

Disturbed airflow resulting from air moving vertically in convective currents

Question 4

What is mechanical turbulence?

Answer 4

Disturbed airflow resulting from air moving past or over obstructions

Question 5

What is wind shear?

Answer 5

Drastic change in wind speed or direction over relatively short distance

Question 6

What is wake turbulence?

Answer 6

Turbulent air (lift) behind aircraft that occurs

Question 7

What is stable air?

Answer 7

Smooth and stable flying conditions since air will resist displacemment

Question 8

What is unstable air?

Answer 8

Lifted and continues to rise on its own since lifted air is buoyant

Question 9

What are signs of stable air?

Answer 9

• Stratus-type cloud or fog
• Low visibility when dust, smoke, haze, or fog are present
• Steady precipitation
• Consistent, steady winds
• IFR conditions for ceiling and visibility

Question 10

What are signs of unstable air?

Answer 10

• Cumuliform clouds
• Good visibility
• Gusty wind
• Showery precipitation
• Thunderstorms

Question 11

What are the two categories of turbulence?

Answer 11

Friction and Thermal

Question 12

What is friction turbulence?

Answer 12

Caused by restriction of the movement of the wind

Question 13

What are the three types of friction turbulence?

Answer 13

• Mechanical turbulence
• Shear turbulence
• Frontal turbulence

Question 14

What is mechanical tubulence?

Answer 14

Result of friction between air and ground, which causes eddies

Question 15

What is shear turbulence?

Answer 15

Result of friction between opposing air currents

Question 16

What is frontal turbulence?

Answer 16

Result of friction between two opposing air masses near frontal surface

Question 17

What is thermal turbulence?

Answer 17

Caused by rapid change of temperature in atmosphere

Question 18

What are the two types of turbulence initiated by heat?

Answer 18

• Daytime convection turbulence
• Cold air advection turbulence

Question 19

What is daytime convection turbulence?

Answer 19

Result of vertical currents caused by unequal heating of Earth’s surface

Question 20

What is cold air advection turbulence?

Answer 20

When cold air moves over warmer water or land, heating from below creates unstable conditions that favour convection currents and turbulence

Question 21

What are the intensities of turbulence?

Answer 21

• Light
• Moderate
• Severe

Question 22

What is macroburst?

Answer 22

Large downburst with horizontal diameter of 4 km or more

Question 23

What is microburst?

Answer 23

A downburst of less than 4 km in diameter

Question 24

What is wet microburst?

Answer 24

Occurs when dry air penetrates saturated air leading to rapid evaporation and cooling of the air

Question 25

What is dry microburst?

Answer 25

Occurs when precipitation evaporates and the air cools and descends

Question 26

What is virga?

Answer 26

Precipitation falling but not reaching the ground

Question 27

How many types of wind shear are there and what are they?

Answer 27

- 2 types - Directional shear - Speed shear

Question 28

What is directional shear?

Answer 28

When two winds blowing from different directions meet

Question 29

What is speed shear?

Answer 29

When two winds are close together and blow from the same direction but at different speeds

Question 30

What are the two classifications of wind shear?

Answer 30

- High-level wind shear (HLWS) - Low-level wind shear (LLWS)

Question 31

What is clear air turbulence (CAT)?

Answer 31

Occurs when fast moving jet stream passes along slow moving one, it disturbs the air and creates turbulence