What components make up earth’s atmosphere?
78% Nitrogen
21% Oxygen
1% argon, CO2, other gases and water vapour
Although water vapour is less than 1% of our atmosphere, it (along with the atmosphere’s ability to expand, contract, nd move) is responsible for fuelling the weather in the atmosphere by transporting heat
Like the layers of earth/dirt, the atmosphere is divided into several layers called ______.
Strata
Each strata is separated by a narrow transition zone known as ____pause (the name of the strata/layer, followed by ‘pause’)
The troposphere is the lowest strata and about __% of earth’s atmospheric mass is concentrated within the troposphere
99%
What are the 5 atmospheric stratas?
- Troposphere (1st layer)
- Stratosphere (2nd layer)
- Mesosphere (3rd layer)
- Thermosphere (4th layer)
- Exosphere
Sometimes thunderstorms can punch through to the stratosphere, but almost all weather happens exclusively within the ____________.
Troposphere
What characterizes/separates/dilineates the different layers of the atmosphere?
Each layer is characterized by differences in their chemical composition. These chemical compoitions produce variations in temperature and lapse rates (how much temp changes over verticle distance
What happens to the temp and lasp rate in the stratosphere?
Standard lapse rate in the trophosphere is 2oC per 1000 feet. A little ways into the stratosphere (within the transition zone called the tropopause) this stays more or less the same but then the temperature actually starts to increase
What are the characteristics of the Troposphere?
- This is the atmospheric layer closest to the planet
- Air is much denser here than it is in the higher layers
- Within the trophosphere temperature decreases at a constant rate of 1.98oC / 1000ft (we call this the Standar Lapse Rate)
- Over 99% of water vapour is found in the trophosphere. This water vapour plays a major role in regulating the air temperature. The water absorbs both the incoming solar energy and the thermal radiation that is re-emitted by the surface of the earth.
The word ‘troposphere’ means ______ __ ______
Region of mixing.
It was given this name because of the vigorous convective air currents. Both the temp and water vapour content in the troposphere decrease rapidly with altitude.
What is the Tropopause?
The boundary/transition layer between the trophosphere and stratosphere.
- Average temp: -56oC
- Marks the top of the weather layer (except for the occasional CB)
- Often indicated by a layer of haze
- Temp remains relatively isothermal (doesnt change much) withtin the tropopause
- Generally smooth flying conditions with little moisture
At what altitudes does the tropopause sit?
Over the poles:
25000ft
Over the equator:
54000ft
**The height also varies by season, being higher in the summer then the winter. The average height overall is 38000ft throughout the globe
Why is weather over the equator more violent/why is the more of it?
Because the boundary (tropopause) is so high over the equator there is simply more tropopause for weather to happen in.
The tropopause is so high because the hot air around the equator is pushing it upward.
How does the stratosphere stop weather?
Because the air temperature increases with altitude in the stratosphere, it does not permit convection.
Convection is the movement of hotter, less dense air rising through/above colder/heavier/denser air.
The air starts out warm, rises, cools, then hits the Stratosphere and is too cold/heavy to rise/push through the warmer air on top.
What is the Stratosphere?
- Sits on top of the tropopause
- Extends up to 180,000ft high
- Atmospheric pressure continues to decrease in this layer
- Air temperature begins to increase in this layer (this is called a Negative Lapse Rate)
Why does the temperature increase within the stratosphere?
Because of the ozon layer that sits in the stratosphere, which absorbs much of the incoming solar radiation. This creates a rise in temperature.
The tropopause is generally arund -56oC but the temp within the stratosphere gradually inceases back up to 0oC at the stratopause (this temp is at the top of the stratosphere/bottom of the stratopause at 180,000ft)
Sitting atop the Stratopause is the Mesophere. What characteristics defines the mesophere?
- Starts at 180,000ft and extends up to 275,000ft
- Temp will start to decrease, at a much more rapid rate than in the troposphere
- Temp gets much, much colder as well. -100oC at an altitude of 275,000ft at the Mesopause.
- There is almost no ozone or water vapour within this layer
- In this layer, gasses beging to form their own layers (strata within a strata!) according to their molecular mass (weight). Heavier gasses get pulled to the bottom layer by gravity
What is the thermosphere?
- Sits atop the mesopause
- Starts at 100km
- Gets HOT. Up to 727 - 1227oC
- These high temps are caused by the intense solar radiation
- This is the layer in which the Northern Lights are formed
- Even at this altitude, the major atmospheric components are still nitrogen and oxygen but these gas molecules are widely separated
What is the exosphere?
- The transitional zone between earth’s atmophere is space
- Upper edge of the layer is undefined (around 10,000km from earth)
What is the point of the ICAO Standard Atmosphere (ISA)?
Meteorologists and engineers needed a ‘baseline’ atmosphere with which they could refer to for the purpose of calculations.
So we basically made one up because there really is no standard because the atmosphere is so dynamic and volatile. This is an ideal/perfect atmosphere and rarely exists in real life.
What are the ISA conditions?
- Sea Level
- 29.92 / 1013 millibars or hectopascals / 14.7lbs/square inch
- 15oC
- 1 inch of mercury drop per 1000ft increase in altitude
- 1.98oC drop per 1000ft increase in altitude
- Dry air mass, no precipitation
If the exam says ‘the temperature is ISA +3’ what does this mean?
What does it mean if you are at an altitude of 10,000ft?
- That the temp is 15+3=18oC
- If we start with 18oC then subtract 2oC x 10 (for 10,000ft) we get -2oC
What are the layers of atmosphere from most to least dense?
Tropo, Strato, Meso, Thermo
Quiz Question: The thickness of the Troposphere varies with:
Parallels of Latitude
Quiz Question:
At FL2000 the OAT is -35oC. the air therefore has an average temperature which is how many degrees colder than ISA?
10 degrees colder
- Standard temp at SL is 15oC
- 20x2 = 40
- 15-40 = 25
- Therefore the standard temp at FL2000 would be -25oC, which is 10 degrees colder than ISA
