1. Properties of the Atmosphere
Section 11.2

2. Temperature
Measured using one of two common scales (Fahrenheit or Celsius); based on the freezing and boiling points of water
The SI unit for temperature is Kelvin; the zero point is absolute zero (the lowest temperature any substance can have)
We discussed the changes in temperature throughout the atmosphere

3. Air Pressure
The pressure exerted on a surface by the weight of the atmosphere above Earth
Pressure = force / area
Units are N/m2
Often measured in millibars (mb)
Air pressure decreases with altitude as the mass of air above you decreases

4. Air Pressure The density of air decreases with altitude
Pressure, temperature, and density are all related in the atmosphere
At the same density warmer air is at a higher pressure than cooler air
At the same temp., air with higher density exerts more pressure than low density air
At the same pressure, warm air is less dense than cool air

5. Temperature Inversion
Temperature inversion – is an increase in temperature with height in an atmospheric layer
In the troposphere occurs with a rapid cooling of land on a cold, clear, calm winter night
Fog or low level clouds; increase pollutants in the air; Smog

6. Wind
In the lower atmosphere, air moves from high density regions to low density regions
Density differences are caused by unequal heating at Earth’s surface
Air moves from a region of high pressure to an area of low pressure
Wind speed is measured in (mph), (km/h), or knots. 1 knot = 1.85 km/h

7. Humidity
The amount of water vapor in the atmosphere at a given location on Earth’s surface
Relative humidity is the amount of water vapor in the air compared to the total amount it can hold; expressed as %
Saturation occurs when the water vapor in a volume of air has reached its maximum amount

8. Humidity
Dew point is the temperature at which air must be cooled at constant pressure to become saturated
Latent heat is the extra thermal energy contained in water vapor compared to liquid water
Adiabatic heating – air is compressed
Adiabatic cooling – air expands

9. Humidity Dry adiabatic lapse rate – 10 oC / 1000 m
Moist Adiabatic lapse rate – 4 oC / 1000 m
Complete Problem Solving Lab on page 283 for a daily grade. Answer #’ 1-5.