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Flashcards in Weather Theory [Block 5] Deck (41)
1

What are the levels of the atmosphere?

Troposphere

Tropopause

Stratosphere

Mesosphere

Thermosphere

2

Troposphere: Temperature Change? Where is it found? Where is it thickest and thinest? What is unique about this layer?

–Temperature decreases with altitude (2ºC per 1000 feet) –Surface to approximately 36,000 feet msl. (Middle Latitudes) –Layer is thinner near the poles and thickest at the Equator –Where most wx occurs

3

Tropopause: Temperature Change? What is it's relation to atmospheric wind and weather?

–Temperature remains relatively constant with increases in altitude –Related to Jet Stream and Thunderstorms

4

Altitude, Pressure, and Tempearture Avg. of

MSL

5,000

10,000

18,000

35,000

50,000

70,000

5

Causes Of Weather

Every physical process of weather is accompanied or the result of what? 

What causes differences in pressure and altimeter settings on Earth?

 

•Every physical process of weather is accompanied by, or is the result of, a HEAT EXCHANGE

•UNEQUAL HEATING of the Earth’s surface causes differences in pressure and altimeter settings

6

The Sun - Convection

What is the sun in relation to weather on Earth?

Where is solar energy greater and warmer?


______ air flows towards _______ and ______ air flows toward _______

•The sun is the energy source which causes weather.

 

1.Solar Energy heats the equator more than the poles.

2.Warm air flows toward poles and cold air flows toward equator.

7

Convection:

Is the atmosphere a closed or open system?

What does the system attempt to do?
What does energy from the sun result in?

Due to these differences what is convection?

•The Atmosphere is essentially a closed system

•This system is constantly attempting to achieve a physical equilibrium

•Energy from the sun results in global differences in temperature and pressure

•The effort to equalize is called Convection

8

Coriolis Force:

What causes it? 

What deflection does it cause?
Where is it more prominent?

•CORIOLIS FORCE is caused by the earth’s rotation

–Deflects winds to the right in the northern hemisphere

–More prominent at higher altitudes away from surface friction

9

International Standard Atmosphere (ISA)
 

Who created it? 

What is the standard at sea-level?
Pressure?  "Hg & mb
Temp?  C & F

•Created by ICAO (International Civil Aviation Organization)

•At sea level, the standard is:

–Pressure: 29.92” Hg. or 1013.2 mb

–Temperature: 15ºC or 59ºF

10

Atmospheric Pressure 

Changes in temperature result in? 

What is an isobar?

What do isobars do? 
Where are strong winds most prevalent ?

•Changes in temperature also result in changes in pressure

•Isobar:

–Lines of equal pressure

•Delineate pressure systems and features

•Tightly packed lines indicate tight pressure gradient =Strong Winds

11

Low Pressure Systems:

What is the flow called? 
Which direction does the flow rotate/ 

What is it's cause? 

•Cyclonic Flow

–Counterclockwise

•Upward Motion of Air

12

High Pressure System:

What is the flow type? 
Which directiond does it flow? 

What does it cause?

•Anticyclonic

–Clockwise Flow

•Downward Motion of Air

13

Dewpoint

Definition


When will air become saturated and what will the relative humidity be? 

What happens when air is saturated? 

What kind of condensation can they turn into?

What determines amoutn of water vapor air can hold?

•The temperature at which air reaches a state where it can hold no more water

–Air will become saturated and have a 100% relative humidity

–Moisture begins to condense into clouds, fog, dew, and/or frost

•Therefore, air temperature determines the amount of water vapor air can hold

14

Temperature and Dewpoint

When dewpoint spread is ___ degrees and _____ at the surface you can expect what? 


If freezing temperatures occur what else can be formed?

•When the temperature dewpoint spread is 5 degrees and decreasing at the surface you should expect:

–Fog

–Low level clouds

•Add freezing temperatures and frost could form

15

Local Wind Pattern Types:

When does each occur? 
What occurs? 
How is air cooled?

Sea-Breeze: Occurs at daylight. Warm air at surface condenses and raises, cool high pressure air from water moves in to replace it. 

 

Land Breeze: Occurs at night. Warmer low pressure air over water rises and cool air flows from land to sea to replace it.

 

*Air is cooled by adiabatic expansion. 

 

16

Radiation Fog: 

When and how does it form?

•Forms in low lying areas on calm, clear nights

•As the ground cools at night, the air temperature at the surface cools to the dewpoint

17

Advection Fog:

How does it form? 

•Forms as the result of warm, moist air condensing as it moves over a cooler surface

18

Upslope Fog: 

•Results from warm, moist air being cooled as it is forced up sloped terrain

–Common in mountain ranges

19

Steam Fog: 

When does it occur?

What dangerous conditions should we look out for with steam fog? 

•Occurs when cold, dry air passes from land to warmer bodies of water

–Low level turbulence can occur

–Icing could become hazardous

20

Types of Airmasses: 

(cA) Continental Arctic: Cool, Dry 

(cP) Continental Polar: Cool, Dry

(mP) Maritime Polar: Cool, Dry

(mT) Maritime Tropical: Warm, Wet

(cT) Continental Tropic: Hot, Dry 

 

 

 

21

Cold Front : 

What kind of movement occurs? 

Can move up to ________ as ________

 

•Cold air moving to displace warmer air

–Can move up to twice as fast

•Narrow lines of showers and

–Could contain severe thunderstorms

22

Warm Front: 

What kind of movement occurs?

Iclement weather over a wider area could contain _____? 

_____ increases gradually as the front approaches.
_________ often procedes the front.

•Warm air moving to displace colder air

•Make for inclement weather over a wider area and could contain embedded thunderstorms

–Rainfall increases gradually as the front approaches

–Fog often precedes the front

23

Stationary Fronts: 

What kind of movement?

How is the equilibrium?

How long can it affect an area
 

•No movement

•Opposing airmasses are relatively balanced

•Can affect an area for several days

•Mixture of weather phenomenon that could last for days

24

Occluded Fronts: 

What kind of movement occurs? 

Which front is faster? 

What is a danger of occluding fronts, including right int he beginning of occlusion. 

•Cold and warm fronts merge together

–Cold fronts usually faster and catch up to the warm front

•Turbulence will be an issue especially when the fronts just begin to occlude

25

Recognizing Air Masses Passage: 
What changes? *TEST QUESTION

•Temperature change

•Wind direction change

–Speed may also change

•Air pressure change

26

Thunderstorms: 
What are they produced in? 


What are severe thunderstorms associated with? 

What are criteria for sever thunderstorms?

What are the ingredients for thunderstorms?

 

•Produced in cumulonimbus clouds

–Large amount of moisture (high humidity)

–Unstable air (lifting action)

 

•Severe Thunderstorms

–Typically associated with frontal systems or drylines.

–Criteria for Severe Thunderstorm:

•Wind in excess of 50 knots, or;

•Hail of ¾ in. diameter or greater, or;

•Tornados

 

•Ingredients

–Moisture

–Lifting action

–Instability

27

Stages of a Thunderstorm

•Stages:

–Cumulus: lifting action (updrafts) of the air begins

–Mature: time of greatest intensity with both updrafts and downdrafts. Precipitation begins

–Dissipating: downdrafts replace updrafts

28

Embedded Thunderstorms: 

What obscures embedded thunderstorms.
May  not be seen from _____ or in ______. 

 

•Embedded Thunderstorms:

–Obscured by other cloud formations

–May not be seen from the ground or in flight

29

Thunderstorm Hazards: (4)

 

How far should you circumnaviage a thunderstorm?
 

•Hazards

–Turbulence

–Lightning

–Hail: may fall for miles outside of the clouds

–Tornados

•Always circumnavigate a thunderstorm by at least 5 nm

30

Virga

What is it? 

•Is a type of precipitation

•Visible wisps or strands of precipitation falling from clouds that evaporate before reaching the surface

31

Turbulence: 

Types: (3)
 

•Mechanical Turbulence

–Obstacles such as trees or buildings disturb smooth air flow

•Convective Turbulence

–Turbulence caused typically by surface heating (thermals)

•Frontal Turbulence

32

Squall Line:
Definition:
What is it capable of ? 

•Squall Line:

–A nonfrontal narrow band of thunderstorms usually ahead of a cold front

–Capable of producing the most severe thunderstorm conditions

33

Microburst:

How fast can they be? 
What are they associated with?
How long do they last?

•Microburst

-Near Thunderstorms

–Can be as strong as 6000 fpm downwards

–Typically associated with convective activity

–Duration rarely in excess of 15 minutes

34

Wind Shear

A point between high velocity winds and lower velocity winds. 

35

Air Stability

Definition:
What is the standard lapse rate? 

As air becomes ________ dewpoint _________ and __________ increases. 

•Atmospheric resistance to vertical motion

•Standard Lapse Rate: 2º per 1000 feet

•As air becomes warmer and dewpoint increases, instability increases

36

Stable Air Characteristics

•Stratiform clouds

•Smooth air

•Low visibility

•Continuous precipitation

37

Unstable Air Characteristics (5)

•Cumuliform clouds and/or clouds with vertical development

–Rising warm air

•Turbulence

•Good visibility

•Showery precipitation

•Higher actual lapse rate

38

Temperature Inversions: 

When do they exist? 
Where do they usually result in? 

Where do they develop usually and under what conditions?
 

What conditions are formed beneath a low level temperature inversion?

What does it act as?

•Exists when the air temperature increases with an increase in altitude

•Usually results in a stable layer of air

•Develops near the ground on clear, cool nights with light winds

•Smooth air and restricted visibility is found beneath a low level temperature inversion

•Act as a “cap” for weather and pollutants

39

Mountain Wave:

What kind of cloud is it?
What shape does it have ? 
What kind of winds are involved?
What will it appear to be?
When can you expect mountain wave turbulence?

•Lenticular Clouds:

–Almond or lens shaped clouds usually found on the downwind side of a mountain

–May contain winds of 50 knots or more

–Appear stationary

•Expect mountain wave turbulence when the air is stable and winds of 40 knots or greater blow across a mountain ridge

40

Structural Icing: 

Conditions necessary?

Freezing rain?

Ice Pellets?

What do Ice pellets indicate? 

•Conditions necessary:

–Visible moisture

–Temperature at or below freezing

•Freezing Rain:

–Usually causes the greatest accumulation of structural ice

•Ice Pellets:

–Caused when rain droplets aloft freeze at a higher altitude

–Indicates that freezing rain exists aloft

41

Icing: 

Types of Ice? (3)

Icing Hazards? (6)

•Types of ice

–Clear

–Rime

–Mixed

 

•Icing Hazards

•Decreases lift

•Decreases thrust

•Decreases visibility

•Increases drag

•Increases weight

•Increases stall speed