ATMO 9/2 Atmosphere and Human Response

- Current Weather
- Hurricanes / Tropical Storms
- Gustav weakened, dissipating and Hannah not where she was forecasted, further south than forecast but should start heading north, northwest
- Ike: Headed toward Cuba in the next 5 days

Vertical Structure of the Atmosphere
Temperature
- 0C by ~3,000 meters
- Tropopause
- Iso thermal (constant temp.) layer above troposphere
- Separates troposphere from stratosphere
- Acts like a "lid" on rising air motion, clouds are confined below tropopause in the troposphere
- Jet stream exists in this layer (10-11km)

- Stratosphere
- Temp. increases as altitude increases
- Ozone causes this temp increase (absorbs UV radiation from sunlight, not a lot of Ozone, just higher than average amounts than anywhere else)
- Protects surface inhabitants from UV radiation

Density
- Number Density: The number of gas molecules per unit volume (About 2.7X10^19 molecules / cm^3 OR 4.4X10^20 molecules / in^3
- More empty space than space taken up by molecules
- Column of Air Example (From Sea Level to Top of Atmosphere)
- Air pushes down on the earth with a force equal to the weight of the entire column of air
- Higher up, the force is much less (less air above)
- Gases, like air, are easily compressed, ie, squeeze it together and it's number density increases
- Air near the earth's surface is compressed by all of the air above, making it more dense. Moving upward from the surface, the air density generally decreases because there is less and less weight pushing down from above.

Pressure
- Air Pressure: From a microscopic view, each time a gas molecule collides with a surface it gives a little "push". The sum total of all the collisions on the surface is air pressure. (Force per area)
- Column of Air Example
- 1" Square column of air from sea level to top of atmosphere
- Air pressure due to weight of air above any chosen point (At sea level: 14.7 lbs / sq. Inch OR 1013mb (millibars))
- Sea Level Pressure range: 980-1013mb
- Air Pressure is caused by the weight of air pushing down from above. Therefore, air pressure must decrease as you move upward, since there is less weight pushing down from above.
- Average pressure in Tucson at 2,500' is 930mb
- 5.5km (18,000 feet) average air pressure is about 500mb (half way through the atmosphere)
- MT. Everest 8.8km (22k') 300mb
- Top of troposphere 11km 250mb
- Since air is a fluid, at any point in the atmosphere the pressure is equal in all directions (up, down, left, right from a given point)

Fraction of Atmosphere Above You By Weight
- Measured Air Pressure At Your Location / Sea Level Pressure (~1,000mb)
- Mt. Lemmon = 730mb, ~30% of the atmosphere is below you

Water and Air
- Water is not compressible, so the pressure increase/decrease is linear (constant density)

Hydrostatic Balance
- Air pressure at any given point in the atmosphere is exactly enough to support the column of air above it.

The Atmosphere and The Weather (Effects on Human Body)
- Humans can survive up to about 20,000 ft above sea level, above this level the body starts to suffer from Hypoxia (brain not getting enough oxygen)
- Ear Popping: Pressure differences between inner ear and outer ear canal separated by the ear drum.