Weather

Question 1

What is the composition of the atmosphere

Answer 1

78% nitrogen
21% oxygen
1% other gases (argon, carbon dioxide, trace other gases)

Question 2

How much water vapor is in the atmosphere

Answer 2

0-5% by volume

Question 3

What does water vapor cause

Answer 3

This small amount of water vapor. 0-5% is responsible for major weather change

Question 4

What are the 4 layers of the atmosphere?

Answer 4

Troposphere
Stratosphere
Mesosphere
Thermosphere

Question 5

What is the layer in the atmosphere called that is in between the troposphere and stratosphere

Answer 5

Tropopause

Question 6

How r the layers of the atmosphere defined

Answer 6

They are defined using 
Thermal characteristics (temp changes)
Chemical composition
Movement
Density

Question 7

Describe the troposphere

Answer 7

4-12miles thick (less over poles/more over equator)

Vast majority of weather/clouds/storms/temp variations occur in troposphere

Standard temperature lapse rate of 2deg per 1000’ of alt gain

Question 8

Describe the stratosphere and above atmosphere levels

Answer 8

Stratosphere- little weather exists here and air remains stable
*clouds occasionally extend here

Mesosphere and thermosphere- have little influence over weather

Question 9

Describe the tropopause

Answer 9

• boundary between the troposphere and stratosphere
• altitude of tropopause varies w/ latitude and season.
• elliptical shaped rather than round
• location of TROPOPAUSE is important bc
  * commonly associated with jet stream
  * possible clear air turbulence (CAT)

Question 10

What is the major cause of weather change

Answer 10

Uneven solar warming

Question 11

How does atmosphere pressure change

Answer 11

• as altitude increases atmospheric pressure decreases

- typically at a rate of 1InHg decrease per 1000’ altitude gain

Question 12

Describe a high pressure system

Answer 12

• outward, downward, clockwise
• characterized by downdrafts and dissipating clouds
• generally areas of dry, descending air, good weather I’d typically associated w/ high pressure systems

Question 13

Describe a low pressure system

Answer 13

• inward, upward, counterclockwise
• characterized by rising air
• generally increasing cloudiness and precipitation
• bad weather is commonly associated with areas of low pressure

Question 14

Describe a convective current

Answer 14

• caused by uneven heating

- cause bumpy, turbulent air sometimes when flying @ low altitudes during warmer weather.

Question 15

Describe low level wind shear (LLWS)

Answer 15

• Associated w/ passing frontal system
• thunderstorms, temperature inversions, strong upper level winds>25knots
• can effect any flight, any pilot, at any altitude.

Question 16

Describe a microburst

Answer 16

• most severe type of (LLWS)
• capable of producing down drafts up to 6000’ per min
• last between 5-15 min
• horizontal diameter of 1-2 miles. Depth of 1000’
• ring of blowing dust is often the only visual cue
• may be indicated by intense rain shaft at surface but VIRGA @ cloud base

Question 17

What determines the type of clouds that form

Answer 17

The stability of the atmosphere

Question 18

What are the 4 cloud classifications

How are the classifications determined

Answer 18

• Low, middle, high, extensive vertical development
• classifications are based on the height of the cloud bases

Low surface - 6500’agl
Middle 6500’agl - 20000’ Agl
High 20000’ Agl + (only in stable air)
Extensive vertical development. Bases in middle to high. But extend into high altitude levels (unstable air, turbulent, usually produce hazardous weather phenomena)

Question 19

What is a ceiling

Answer 19

Lowest layer of clouds reported as broken or overcast

Question 20

What r the 4 types of fronts

Answer 20

Warm
Cold
Stationary
Occluded

Question 21

Describe a warm front

Answer 21

• when a warm air mass advances and replaces a body of colder air
• move slowly (10-25mph)
• light to mod precipitation is probable.
• visibility is poor
• the warm front slope slides over the top of the cooler air and gradually pushes the cool air out of the area.
• as the air is lifted it cools and condensation occurs

Question 22

Describe a cold front

Answer 22

• When a mass of cold, dense, stable air advances and replaces a body of warmer air
• moves more rapidly (25-30mph) extreme cold fronts up to 60mph
• acts like a snowplow scooping and lifting underneath warm air forcing it aloft
• lifting warm air creates clouds
• the type of clouds depends on the stability of the warm rising air

Question 23

Comparison of warm and cold fronts

Answer 23

Speed

  - warm (10-25mph)
  - cold (25-30mph up to 60mph)

Slope

  - warm= over the top gradually pushing out
  - cold = steeper plowing under and forcing warm air up and out

Convective activity

  - warm = not typically associated 
  - cold = typically occurs on the frontal boundary/ squall lines can form during summer up to 200 miles in advance 

Type of weather

  - warm =low ceilings/ poor visibility/ rain showers
  - cold = sudden storms/ gusty winds/ turbulence/ hail or tornadoes possible

Weather Warning provided
- warm = provide advance warning of approach/ can take days to pass through a region
- cold = fast approaching w/ little to NO warning
= bring about complete weather change in just a few hrs/ weather clears rapidly and drier air w/ unlimited visibility prevails

Question 24

Describe a stationary front

Answer 24

• 2 air masses forces of relatively equal power meet the boundary separating them remains stationary.
• can influence local weather for days
• weather can be a mixture of both warm and cold fronts