Wind

Question 1

What is the definition of wind?

Answer 1

Wind is the horizontal movement of air.

Wind is always referred to in terms of the direction it is blowing FROM.

Question 2

How is a ‘Southerly’ wind defined?

Answer 2

A ‘Southerly’ wind is blowing from South to North.

The term indicates the origin of the wind’s movement.

Question 3

How is a ‘Northerly’ wind defined?

Answer 3

A ‘Northerly’ wind is blowing from North to South.

Like other wind terms, it describes the direction from which the wind originates.

Question 4

What is the pressure gradient?

Answer 4

The rate of change of atmospheric pressure in the horizontal.

Question 5

What happens when the pressure gradient is steep?

Answer 5

Isobars are spaced closely together on a weather chart, and the winds are strong.

Question 6

What is the Coriolis force?

Answer 6

The deflective force caused by Earth’s rotation, deflecting air to the right in the northern hemisphere.

Question 7

What type of circulation does the Coriolis force create in high pressure systems?

Answer 7

Clockwise circulation.

Question 8

What type of circulation does the Coriolis force create in low pressure systems?

Answer 8

Counterclockwise circulation.

Question 9

How does friction affect low level winds?

Answer 9

It causes them to have different directions and speeds compared to upper winds.

Question 10

What effect does friction have on wind speed over the ground?

Answer 10

It results in slower wind speeds.

Question 11

What is the typical maximum angle at which wind blows across isobars due to friction?

Answer 11

Typically 30°.

Question 12

How does wind behave over water compared to land due to friction?

Answer 12

Wind speed and direction are less affected over water.

Question 13

At what altitude do the effects of friction usually not extend beyond?

Answer 13

2,000 - 4,000 ft above the surface.

Question 14

What is centrifugal force in the context of wind?

Answer 14

A force that can cause air to move in a direction when isobars are curved.

Question 15

What is the effect of veering in wind direction?

Answer 15

A clockwise change in direction.

Question 16

What is a gust?

Answer 16

A rapid change of wind speed or direction of brief duration.

Question 17

What are the two main causes of gusts?

Answer 17

• Mechanical turbulence
• Unequal heating of the Earth’s surface

Question 18

What is a squall?

Answer 18

A rapid change of wind speed or direction of prolonged duration.

Question 19

What causes squalls?

Answer 19

Rapidly moving cold fronts or thunderstorms.

Question 20

What are diurnal effects in wind patterns?

Answer 20

Variations in wind between day and night.

Question 21

What happens to surface wind during the day?

Answer 21

It tends to veer and increase.

Question 22

What happens to surface wind during the night?

Answer 22

It tends to back and decrease.

Question 23

What is a land breeze?

Answer 23

Wind blowing from the land to the water at night.

Question 24

What is a sea breeze?

Answer 24

Wind blowing from the water to the land during the day.

Question 25

What are katabatic winds?

Answer 25

Winds that blow down ice-free slopes at night or down ice-covered slopes day and night.

Question 26

What causes katabatic winds at night?

Answer 26

Cold air flowing into the valley from cooler slopes.

Question 27

What are anabatic winds?

Answer 27

Winds that occur when slopes warm more quickly than the valley bottom.

Question 28

What is the barrier effect in topographic wind patterns?

Answer 28

A mountain barrier acts as a dam, holding back air and deflecting it parallel to the range.

Question 29

What is the funnel effect in topographic wind patterns?

Answer 29

Wind gushes through a pass in the mountain range with considerable speed.

Question 30

What is the valley effect in wind patterns?

Answer 30

A weak surface wind that follows a well-defined valley.

Question 31

What are mountain waves?

Answer 31

Waves that occur as air crosses mountain ranges.

Question 32

What is a cap cloud?

Answer 32

A cloud that lies over the tops of mountain ranges, indicating a strong downdraft.

Question 33

What is a rotor cloud?

Answer 33

A cloud formed downwind from each wave crest.

Question 34

What are roll clouds?

Answer 34

Roll clouds resemble a long line of stratocumulus cloud lying parallel to the range.

Question 35

What is a lenticular cloud?

Answer 35

Lenticular clouds form in the wave crests aloft and can be hundreds of miles long.

Question 36

What is the maximum height that mountain waves can reach?

Answer 36

Mountain waves can reach heights of up to 30,000 feet.

Question 37

What are the effects of mountain waves on downdrafts?

Answer 37

Mountain waves can produce strong downdrafts of up to 2,000 feet per minute or more.

Question 38

What happens to altimeter readings at the crests of mountain waves?

Answer 38

The altimeter tends to read high at the crests due to low pressure created by high winds.

Question 39

What is wind shear?

Answer 39

Wind shear generates eddies between two wind currents of differing velocities.

Question 40

What causes low-level wind shear?

Answer 40

Low-level wind shear occurs when wind above a low-level temperature inversion is strong while winds below are calm.

Question 41

Fill in the blank: Wind shear is virtually certain where winds from 2,000 - 4,000 feet are _______.

Answer 41

25 kts or more.

Question 42

What is frontal zone wind shear?

Answer 42

Frontal zone wind shear is greater during winter due to higher thermal contrast.

Question 43

What is increased performance wind shear?

Answer 43

Increased performance wind shear occurs when airspeed increases due to entering increased headwind or decreased tailwind.

Question 44

What is decreased performance wind shear?

Answer 44

Decreased performance wind shear occurs when airspeed decreases due to entering decreased headwind or increased tailwind.

Question 45

What are the two types of wind shear?

Answer 45

Wind shear can be either horizontal or vertical.

Question 46

What are jet streams?

Answer 46

Jet streams are strong upper winds that develop where there is a strong horizontal temperature gradient.

Question 47

What is the minimum wind speed for a jet stream?

Answer 47

The wind speed must be at least 60 knots.

Question 48

Where do jet streams lie in relation to frontal systems?

Answer 48

Jet streams lie to the north of frontal systems where the temperature gradient is greatest.

Question 49

What is clear air turbulence (CAT)?

Answer 49

CAT is all turbulence not related to convective activity, usually above 15,000 feet AGL.

Question 50

What is a key characteristic of jet streams?

Answer 50

Jet streams have substantial horizontal and vertical wind shear.

Question 51

What is the relationship between the tropopause and jet streams?

Answer 51

The tropopause height is higher over the equator than over the poles and moves with the air mass.

Question 52

What can cause a rapid loss or gain of airspeed?

Answer 52

Low-level wind shear can result in a rapid loss or gain of airspeed.

Question 53

True or False: Wind shear is only associated with changes in wind speed.

Answer 53

False.

Question 54

What does CAT stand for in aviation meteorology?

Answer 54

Clear Air Turbulence ## Footnote CAT is turbulence that occurs in clear air, typically associated with jet streams.

Question 55

When is CAT more common?

Answer 55

In winter ## Footnote CAT is stronger in winter than in summer due to atmospheric conditions.

Question 56

How do jet streams behave in mid latitudes during winter?

Answer 56

They shift to the south ## Footnote This shift can influence weather patterns and turbulence.

Question 57

Where is CAT usually located in relation to the jet stream?

Answer 57

On the polar side of the jet in the trough area ## Footnote This positioning is crucial for understanding flight conditions.

Question 58

True or False: CAT is more prevalent in summer than in winter.

Answer 58

False ## Footnote CAT is actually more common in winter.

Question 59

Fill in the blank: CAT is usually found in the _______ side of the jet stream.

Answer 59

polar ## Footnote The positioning of CAT is important for pilots to understand.