Current Weather:
- Gustav Hurricane/Tropical Storm
- Headed toward the Louisiana area according to forecast
Tucson Weather:
- Typical monsoon like weather patterns with SE flowing winds
- Looking for something to develop near Safford area which would travel SE to Tucson
Lecture:
The Atmosphere
- Outer layer of gases and aerosols that surround a planet
- On Earth, the Atmosphere is very thin (500km compared to Earth's radius of 6,370km)
- Troposphere contains all weather and clouds. Also contains about 75% of atmosphere by weight (75% of all gases)
- Extended from sea level to about 11km
- As you o further up, the atmosphere fades into outer space around 500km
- Gases are lighter than all other elements on the earth, so it flows to the outer edges of the planet. Atmosphere was formed by gases being released by volcanic eruptions.
- Humans are so well adapted to the 20% O2 atmosphere in the lowest 4km, we need it to survive.
Weather:
- The interaction of water vapor, aerosols, and convection currents
- Earth heats mostly around the equator, causing convection currents and jet streams
- Circulations that develop are trying to even temperature differences caused by uneven heating
- Earth's rotation complicates the motion of currents, causing them to spiral
- Water evaporates at the surface and re-condenses in the atmosphere (Essential for life on land)
- It takes a lot of energy (from the sun) to evaporate the water, the energy is carried along with the evaporated water (water vapor) and is very important to the formation of storm systems
Life Essential Functions of the Atmosphere
- Respiration
- Shield from UV radiation
- Protection from meteor collisions with the surface (they burn up in the atmosphere)
- Equalizes temperature differences caused by uneven heating on the Earth's surface
- Keeps the air temperature at the surface 60F warmer as compared to if there was no atmosphere
Atmosphere make up:
- Nitrogen 78%
- Oxygen 21%
- Water Vapor 0-4%
Greenhouse Gases:
- Water Vapor
- CO2 (Increased over 35% since 1750 (industrial revolution))
- Methane
- Nitrous Oxide
Ozone:
- 20-30km above ground surface protects animals and plants from harmful UV radiation
- Ozone near ground is a toxic pollutant
Photo chemical Smog:
- Vehicle exhaust mixed with sunlight and chemical reaction causes Ozone
Aerosols:
- Affect passage of solar radiation through the atmosphere
- Influence cloud formation (water vapor bond to aerosols)
- Man made aerosols can change the type of clouds that form
- Particulate air pollution (small aerosols that can enter the respitory system)
Vertical Structure of the Atmosphere:
Temperature
- As the average speed of individual molecules increases, the temperature increases
- At 0C, the average speed of individual molecules is roughly 1100 MPH
- This random speed is called thermal or kinetic motion
- A thermometer senses the average speed of molecules and is calibrated to indicate the temperature associated with the average speed of the molecules
- Temperature decreases with altitude in the troposphere, stays constant through the tropopause, and increases with altitude through the stratosphere
- Temperature decreases at an average rate of 6.5C per 1000 meters (3.6F per 1000 meter)
- Temperature inversions
- In troposphere, a layer of air where air temperature increases with increasing altitude
- Common near the ground in late night/early morning
- In the late afternoon the air in the lower half of the troposphere can be warmer than the day's average temperature
- In the early morning, the ground is cooler than the air above it, in effect cooling the air just above the ground causing a temperature inversion
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