Unit 7

Question 1

What is the primary cause of weather?

Answer 1

unequal surface heating → causes diff in pressure

Question 2

Coriolis force

Answer 2

deflects winds to the right in the N Hemisphere (caused by Earth’s rotation)

Question 3

Air parcel

Answer 3

imaginary volume of air where all basic properties of atmospheric air may be assigned

Question 4

Structure Atmosphere

Troposphere

Answer 4

layer from surface → 7 mi

altitude increase = temp decrease

Question 5

Structure Atmosphere

Tropopause

Answer 5

transition zone between troposphere & stratosphere

altitude increases = wind & temp decrease

Question 6

Structure Atmosphere

Stratosphere

Answer 6

4 -12 mi

Disadvantage flying: more fuel consumption (b/c warmer temp), more radiation, more ozone

Question 7

Dew point

Answer 7

temp air must be cooled to become saturated by water vapor already present

Question 8

What happens when temperature & dew point converge?

Answer 8

fog, clouds, rain form

Question 9

Stable atmosphere

Answer 9

resists any upward/downward displacement

Question 10

Stable air

Answer 10

stratiform clouds & fog

continuous precipitation

Question 11

Unstable air

Answer 11

cumuliform clouds

showery precipitation

Question 12

Adiabatic

Answer 12

changes where no heat is removed/added to air

Question 13

Convective currents

Answer 13

localized vertical air movements

Cause turbulence (low altitudes)

Question 14

Fronts

Answer 14

temp, humidity, wind often change rapidly over short distances across a frontal zone

Question 15

Requirements in air for thunderstorm to form:

Answer 15

• Sufficient water vapor
• Unstable lapse rate
• Initial lifting to start strom process motion

Question 16

Thunderstorm stages: Cumuls

Answer 16

building stage when there are (continuous updrafts)

Question 17

Thunderstorm stages: Mature

Answer 17

greatest intensity (both updrafts & downdrafts)

severe wind shear/turbulence, precipitation begins

Question 18

Thunderstorm stages: Dissipating

Answer 18

storm raining itself out (only downdraft)

Question 19

Squall-line thunderstorms

Answer 19

most severe conditions (hail, destructive winds, tornadoes…)

Narrow thunderstorm usually ahead of a cold front

Question 20

Clear ice

Answer 20

water droplets touch plane & flow across surface before freezing (smooth sheet)

Question 21

Rime ice

Answer 21

water droplets are small & freeze without spreading (rough shape)

Less lift, more drag

Question 22

Mountain wave

Answer 22

stable air crosses mountain barrier → air flowing up wind side (smooth) & wind across barrier (layers)

Question 23

Wind shear

Answer 23

generates whirls of air (eddies) between 2 wind currents of diff velocities

Hazards: low-level temp inversions, frontal zones, clear air turbulence

Question 24

When air temp within 5ºF of dew point & spread decreasing expect…

Answer 24

fog or low clouds

Question 25

Greatest turbulence is in what type of cloud?

Answer 25

cumulonimbus clouds

Question 26

Characteristics of stable air:

Answer 26

• Startform clouds
• Smooth air
• Fair/poor visibility in haze & smoke
• Continuous precipitation
• Cool
• Dry

Question 27

Characteristics of unstable air:

Answer 27

• Cumuliform clouds
• Turbulent air
• Good visibility
• Showery precipitation
• Warm
• Humid

Question 28

The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly.

Answer 28

This difference in direction is primarily due to friction between wind & surface

Question 29

You are avoiding a thunderstorm that is in your flightpath. You are over 20 miles from the cell; however, you are under the anvil of the cell. Is this a hazard?

Answer 29

Yes, hail can be discharged from the anvil.

Question 30

The presence of ice pellets at the surface is evidence that there

Answer 30

is a temperature inversion with freezing rain at higher altitudes

Question 31

Which conditions result in the formation of frost?

Answer 31

The temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dew point is below freezing.

Question 32

Low-level turbulence can occur and icing can become hazardous in which type of fog?

Answer 32

Steam fog

Question 33

In which situation is advection fog most likely to form?

Answer 33

Air moving inland from the coast in winter

Question 34

The stability of an air mass can usually be determined by

Answer 34

cloud types & types of precipitation

Question 35

Temperature and radiation variations over land with a clear sky typically lead to

Answer 35

minimum temperature occurring after sunrise

Question 36

At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82°F and the dewpoint is 38°F?

Answer 36

10,000 ft AGL