Weather Flashcards
What is the composition of the atmosphere
78% nitrogen
21% oxygen
1% other gases (argon, carbon dioxide, trace other gases)
How much water vapor is in the atmosphere
0-5% by volume
What does water vapor cause
This small amount of water vapor. 0-5% is responsible for major weather change
What are the 4 layers of the atmosphere?
Troposphere
Stratosphere
Mesosphere
Thermosphere
What is the layer in the atmosphere called that is in between the troposphere and stratosphere
Tropopause
How r the layers of the atmosphere defined
They are defined using Thermal characteristics (temp changes) Chemical composition Movement Density
Describe the troposphere
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
Describe the stratosphere and above atmosphere levels
Stratosphere- little weather exists here and air remains stable
*clouds occasionally extend here
Mesosphere and thermosphere- have little influence over weather
Describe the tropopause
- 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)
What is the major cause of weather change
Uneven solar warming
How does atmosphere pressure change
- as altitude increases atmospheric pressure decreases
- typically at a rate of 1InHg decrease per 1000’ altitude gain
Describe a high pressure system
- 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
Describe a low pressure system
- inward, upward, counterclockwise
- characterized by rising air
- generally increasing cloudiness and precipitation
- bad weather is commonly associated with areas of low pressure
Describe a convective current
- caused by uneven heating
- cause bumpy, turbulent air sometimes when flying @ low altitudes during warmer weather.
Describe low level wind shear (LLWS)
- Associated w/ passing frontal system
- thunderstorms, temperature inversions, strong upper level winds>25knots
- can effect any flight, any pilot, at any altitude.
Describe a microburst
- 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
What determines the type of clouds that form
The stability of the atmosphere
What are the 4 cloud classifications
How are the classifications determined
- 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)
What is a ceiling
Lowest layer of clouds reported as broken or overcast
What r the 4 types of fronts
Warm
Cold
Stationary
Occluded
Describe a warm front
- 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
Describe a cold front
- 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
Comparison of warm and cold fronts
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
Describe a stationary front
- 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
