Weather Theory

Question 1

Atmospheric Composition

Answer 1

78% Nitrogen
21% Oxygen
1% Other

Question 2

Troposphere

Answer 2

Lowest level of atmosphere.

Nearly all weather occurs here.

As altitude goes up temperature goes down.

Question 3

Tropopause

Answer 3

Boundary between Troposphere and Stratosphere.

Question 4

Stratosphere

Answer 4

Temp gradually increases as altitude goes up.

Question 5

Standard Atmosphere

Answer 5

Datum for temperature and pressure at specific altitudes.

At sea level standard is:
15 Degrees C
29.92 hg

Lapse rate is every 1000ft up you drop 2 degrees C.

Question 6

Indicators of Stable Atmosphere

Answer 6

Poor visibility
Stratiform Clouds
Continuous Precipitation
Absence of Turbulence

Question 7

Indicators of UNstable Atmosphere

Answer 7

Good visibility
Cumuliform Clouds
Scattered Precipitation
Turbulent Air
Thunderstorms

Question 8

What is convection?

Answer 8

Upward and downward movement of air.

Question 9

Three forces affecting wind heading and speed?

Answer 9

Pressure Gradient Force

Coriolis Force

Friction

Question 10

How does pressure travel?

Answer 10

High to Low

Carries winds

Question 11

What is Wind Shear?

Answer 11

Air Currents of differing velocities create friction or Shear between them. Inside the shear zone is a nasty mix of eddies and whirls.

Question 12

Temperature Inversion

Answer 12

May exist anywhere

Most commonly found on clear, calm, cool nights.

The land cools more rapidly than the air, cooling the air directly above it faster than the air aloft.

May cause poor visibility.

May cause structural Icing.

Question 13

What does evaporate mean?

Answer 13

Turn to vapor

Question 14

What is humidity?

Answer 14

Moisture in the air

Question 15

What is relative humidity?

Answer 15

Saturation level of the air, expressed as a %

Question 16

What is Dew Point?

Answer 16

The Temperature at which the are would become 100% saturated by the moisture already present.

Question 17

What is Temperature-Dew Point Spread?

Answer 17

Current Temperature - Current Dew Point

If spread is = 0 degrees, the relative humidity is 100%

Typically a Surface Spread Less than or equal to 5 degrees C will result in fog.

Question 18

What is condensation?

Answer 18

Vapor to liquid

Question 19

What is Sublimation?

Answer 19

Vapor straight to Ice

Question 20

What is Super-Cooled Water?

Answer 20

Unfrozen water at a temperature below 0 degrees C

May freeze upon impact, causing structural icing.

If dew point is less than 0 deg C, water vapor tends to skip the liquid stage.

Question 21

What is an Air Mass?

Answer 21

Large body of air having fairly uniform properties of temperature and moisture.

Question 22

Types of Air Masses by Temperature?

Answer 22

Arctic - cold air formed over large bodies of ice or snow, typically at the poles.

Polar - cool air from the upper latitudes

Tropical - Warm air from the lower latitudes and equatorial areas.

Question 23

Types of Air Masses by Moisture Content?

Answer 23

Continental - Formed over land,

Maritime - Formed over water.

Question 24

5 Possible Classifications of Air Masses?

Answer 24

Continental Arctic - Cold, Dry

Continental Polar - Cold, Dry

Continental Tropical - Hot, Dry

Maritime Polar - Cool, Moist

Maritime Tropical - Warm, Moist

Question 25

What is a Front?

Answer 25

Zone in between two Air Masses.

Question 26

What might you experience at a Front?

Answer 26

Wind direction, speed or both may change rapidly. Possible wind shear Temperature changes rapidly Pressure changes rapidly Altimeter settings change rapidly

Question 27

What is a Cold Front?

Answer 27

Leading edge of advancing cold air mass.

Question 28

What happens when a cold air mass encounters a warm air mass at the surface?

Answer 28

A cold front will replace the less dense warm air mass.

Question 29

What is a Warm Front?

Answer 29

Leading edge of advancing Warm air mass. Typically move half as fast as a Cold Front.

Question 30

What is an Occluded Front?

Answer 30

Faster Cold Front overtakes slower Warm Front.

Question 31

What is a Squall Line?

Answer 31

Narrow band of fully developed Thunder Storms

Question 32

What is a Dry Line?

Answer 32

Low Level Boundary separating moist air from dry air.

Question 33

Height for low clouds?

Answer 33

Surface - 6500ft

Question 34

Height for middle clouds?

Answer 34

6,500 - 23,000ft

Question 35

Height for High clouds?

Answer 35

16,500 - 40,000ft

Question 36

Cumulus clouds

Answer 36

Big, lumpy, billowy clouds cumulus = accumulation Result of convection Typically indicate unstable atmosphere

Question 37

Stratus clouds

Answer 37

Uniform, sheet like clouds Result of stable air cooling

Question 38

Nimbus clouds

Answer 38

Clouds from which rain is falling

Question 39

Fractus clouds

Answer 39

clouds broken into fragments

Question 40

High altitude clouds

Answer 40

Cirrus Cirrocumulus Cirrostratus All typically thin and white in appearance

Question 41

Mid Altitude Clouds

Answer 41

Altocumulus - wave pattern Altostratus - Cover the sky allowing very little light.

Question 42

Low altitude clouds

Answer 42

Stratus Stratocumulus Nimbostratus Cumulus

Question 43

Clouds with extensive vertical development

Answer 43

Towering Cumulus Cumulonimbus

Question 44

Convective Turbulence

Answer 44

Result of uneven heating of Earth's surface

Question 45

Mechanical Turbulence

Answer 45

Obstructions to wind flow causes turbulence

Question 46

Mountain Wave turb

Answer 46

Wind forms a wave pattern after passing over mountain

Question 47

Wake turbulence

Answer 47

Fall downward and outward Carried by wind if any

Question 48

What needs to be there for a Thunder storm to form?

Answer 48

Sufficient moisture Unstable atmosphere Updrafts

Question 49

How do updrafts occur?

Answer 49

Surface heating Winds pushed up sloping terrain Converging winds All of the above

Question 50

Three stages of Thunder Storm

Answer 50

Cumulus Mature Dissipating

Question 51

Cumulus Stage

Answer 51

Characterized by updrafts Growth rate up to 3000 FPM The cloud and rain drops grow in size

Question 52

Mature Stage

Answer 52

Characterized by Precipitation, Updrafts, and Downdrafts. Extremely powerful downdrafts = Microburst Thunderstorm hazards reach greatest effect.

Question 53

Dissipating Stage

Answer 53

Characterized by Downdrafts Storm dies rapidly No rain/downdrafts = no more thunderstorm

Question 54

Microbursts

Answer 54

An extremely powerful downdraft May occur anywhere thunderstorms, precipitation, or virga occurs. Typically lasts 10 - 20 min Most dangerous when landing No known techniques can get you out of one.

Question 55

Three types of icing?

Answer 55

Induction Icing Instrument Icing Structural Icing

Question 56

Induction Icing

Answer 56

Ice accumulation blocking air from reaching the engine.

Question 57

Instrument Icing

Answer 57

Icing of the pitot tube and or static source Causes erroneous reading of: - Airspeed Indicator (ASI) - Altimeter - Vertical Speed Indicator (VSI)

Question 58

Structural Icing

Answer 58

Visible Moisture Super-cooled water droplets may increase rate of structural icing. Three Types: - Clear - Forms when water droplet continues to spread, freezing slowly. Smooth sheet of heavy, and hard ice. Most dangerous. - Rime - Formed by smaller droplets freezing rapidly. White, opaque appearance. Rough surface. - Mixed - Combination of clear and rime ice. Heavy and rough.

Question 59

PAIRUS Acronym for Fog

Answer 59

Precipitation Advection Ice Radiation Upslope Steam

Question 60

Precipitation fog

Answer 60

Forms as warmer precipitation falls through colder air, saturating the air as it evaporates.

Question 61

Advection fog

Answer 61

Forms as moist air moves over colder ground or water.

Question 62

Ice fog

Answer 62

fog composed of Ice cyrstals

Question 63

Radiation fog

Answer 63

Terrestrial radiation from the cooling ground cools the air above it.

Question 64

Upslope fog

Answer 64

Forms as moist stable air is pushed up sloping terrain.

Question 65

Steam fog

Answer 65

Forms when cold air moves over warm water.