1. Layers of the Atmosphere

2. Layers
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

3. Defining Characteristics
Thermal (Temperature Changes)
Chemical Composition
Movement
Density
Layers are bound by “pauses” where the greatest changes in these characteristics occur

4. Troposphere Lowest layer of atmosphere
Next layer above the troposphere is the stratosphere
Border between troposphere and stratosphere is called the tropopause
Lowest layer of troposphere that touches the Earth is called the planetary boundary layer

5. Troposphere
Contains 75% of the atmosphere’s mass and 99% of its water vapor & aerosols
Begins at Earth’s surface and extends 4-12 miles
Almost all weather occurs here
Height varies at equator and poles. At equator, the height is miles. At poles it is under 4 miles. Also varies with season. Low in winter, high in summer.

6. Traveling up in the Troposphere
Density of gases decrease with height
The air becomes thinner and colder as you go upward
Water vapor decreases with height (water vapor condenses out)
Pressure is greatest at sea level and decreases with height

7. Troposphere Flow
Wind/weather patterns generally move from west to east (if interrupted, can go from north to south or south to north)

8. Stratosphere
Extends around 31 miles above the Earth’s surface (can be 4 to 12 miles)
Holds 19% of the atmosphere’s gases but very little water vapor

9. Stratosphere Temperature
Temperature increases with height
Heat produced through the process of Ozone formation
Temperature goes from about -60 deg F (at the tropopause to a max of about 5 deg F at the top of the stratosphere

10. Temp Divide in the Stratosphere
Since the air in the stratosphere is warmer at the top of the layer and cooler at the bottom layer, there is no “convection”
There is no upward movement of gases
But winds are fast! Moving at 199 mph: “Jet Streams”

11. Mesosphere Extends 31- 53 miles above Earth’s surface
Temp in this layer deceases as altitude increases
Upper boundary is call the mesopause, the coldest naturally occurring place on Earth with temps below -226 deg F

12. Hard to Study the Mesosphere
Weather balloons and other aircrafts cannot fly high enough to reach the mesosphere
Satellites orbit above it, cannot directly measure traits
Use rockets to sample this layer, but flights are brief and infrequent

13. Mesosphere Most meteors vaporize here
Some material from meteors linger so this layer will have a high concentration of iron and other metals
Can sometimes have clouds near the poles called “noctilucent clouds”

14. Thermosphere
Extends from about 56 miles to a range of 311 to 621 miles
Right below the exosphere
Boundary between the thermosphere and exosphere is called the thermopause

15. The Thermosphere is HOT
Temperatures climb QUICK in the lower thermosphere, then level off and stay steady with increasing altitude
Temp is hot due to solar activity
Typically about 360 deg F hotter in daytime than night
Temps in upper Therm can range from about 932 deg F to 2,000 deg F or higher

16. Thermosphere to us?
The thermosphere would feel cold to us, just a little below freezing
WHY?? The individual air particles can hold a lot of heat BUT they are very few and very far apart
There’s not enough kinetic energy between those particles to make it seem hot to us

17. Thermosphere and Space
Air density is SO low that most of this layer is what we consider outer space
The space shuttle and International Space Station both orbit Earth in this layer
X-ray radiation is absorbed here

18. Thermosphere Waves
High-energy solar photons strip off electrons from atoms in this layer and create ions
Just like the ocean, the thermosphere has “waves” and “tides”
These “waves” and “tides” move the ions around and can create electrical currents

19. The Aurora The “Southern and Northern Lights”
Charged particles (ions) from space collide with molecules in the thermosphere and “excite” them into a higher energy state
Those excited molecules shed this excess energy by emitting light

20. Exosphere The most outer layer
Gradually fades into the vacuum of space
Air is extremely thin, gas atoms BARELY collide
Basically the same as outer space

21. Where does the exosphere start?
When the sun is active around the peak of the sunspot cycle it can “puff up” the thermosphere, which moves the boundary of where the exosphere starts (thermopause)
Sometimes the start of the exosphere will be at 620 miles, and sometimes at 310 miles
So the start really depends on how active the sun is

22. Is it part of our atmosphere?
Scientists disagree whether its really a part of the Earth’s atmosphere
Some think the exosphere is just a part of space
Other scientists do actually consider it part of our atmosphere

23. Where does the Exosphere end?
No clear upper boundary
Gradually fades into outer space
Some consider the outermost limit to be at about 120,000 miles, which is about halfway to the moon

24. Geocorona A luminous part of the exosphere that gives off a UV glow
Caused by the scattering of UV radiation by straggling hydrogen atoms that are barely hanging on by Earth’s gravitational pull
Occurs at about 62,000 miles

25. Leaking Atmosphere
Gas particles in the exosphere sort of travel in curved, arched paths (imagine shooting a cannon ball and it arching back to Earth)
Particles travel outward but then get arched back in by gravity to be returned to the lower atmosphere
Some particles are moving too fast to be pulled back in and escape into space