1. Objectives Review Vocabulary
Section 11.2
Properties of the Atmosphere
Objectives
Identify three properties of the atmosphere and how they interact.
Explain why atmospheric properties change with changes in altitude.
Review Vocabulary
density: the mass per unit volume of a material

2. Section 11.2
Properties of the Atmosphere
Atmospheric properties such as temperature, air pressure, and humidity describe weather conditions.
New Vocabulary
temperature inversion
humidity
saturation
relative humidity
dew point
latent heat

3. Section 11.2
Properties of the Atmosphere
Temperature
Particles have more kinetic energy when they are moving faster, so the higher the temperature of a material, the faster the particles are moving – temperature is a measurement of the speed of the particles.
Heat is the transfer of energy that takes place due to difference in temperature.

4. Temperature Measuring temperature
Section 11.2
Properties of the Atmosphere
Temperature
Measuring temperature
Temperature can be measured in degrees Fahrenheit, degrees Celsius, or in kelvin.

5. Section 11.2
Properties of the Atmosphere
Air Pressure
Air pressure is the pressure exerted on a surface by the weight of the atmosphere above the surface. ( P = Force/area)
The units for pressure are N/m2.
Air pressure is often measured in units of millibars (mb), where 1 mb equals 100 N/m2.

6. Air Pressure Density of air
Section 11.2
Properties of the Atmosphere
Air Pressure
Density of air
The density and pressure of the layers of the atmosphere decrease as altitude increases.
The air gets thinner as you go up.

7. Air Pressure Pressure-temperature-density relationship
Section 11.2
Properties of the Atmosphere
Air Pressure
Pressure-temperature-density relationship
In the atmosphere, the temperature, pressure, and density of air are related to each other.

8. Air Pressure Pressure-temperature-density relationship
Section 11.2
Properties of the Atmosphere
Air Pressure
Pressure-temperature-density relationship
Temperature, pressure, and density are all related to one another.
If temperature increases, but density is constant, the pressure increases.
If the temperature increases and the pressure is constant, the density decreases.

9. Air Pressure Temperature inversion
Section 11.2
Properties of the Atmosphere
Air Pressure
Temperature inversion
A temperature inversion is an increase in temperature with height in an atmospheric layer.

10. Air Pressure Temperature inversion
Section 11.2
Properties of the Atmosphere
Air Pressure
Temperature inversion
On cold clear winter nights, the ground is cold and does not radiate heat to the lower layers of the atmosphere. So the lower layers of air become cooler than the air above them.

11. Air Pressure Temperature inversion
Section 11.2
Properties of the Atmosphere
Air Pressure
Temperature inversion
A temperature inversion can lead to fog or low-level clouds.
In some cities, a temperature inversion can worsen air-pollution problems.(smog)

12. Air Pressure Wind The movement of air is commonly known as wind.
Section 11.2
Properties of the Atmosphere
Air Pressure
Wind
The movement of air is commonly known as wind.
In the lower atmosphere, air generally moves from regions of higher density and pressure to regions of lower density and pressure.

13. Section 11.2
Properties of the Atmosphere
Air Pressure
Wind
Near Earth’s surface, wind is constantly slowed by the friction that results from contact with surfaces including trees, buildings and hills.
Higher up from Earth’s surface, air encounters less friction and wind speeds increase.

14. Section 11.2
Properties of the Atmosphere
Humidity
Humidity is the amount of water vapor in the atmosphere at a given location on Earth’s surface.

15. Section 11.2
Properties of the Atmosphere
Saturation occurs when the amount of water vapor in a volume of air has reached the maximum amount possible for that temperature.
(RH = 100%)

17. Humidity Relative humidity
Section 11.2
Properties of the Atmosphere
Humidity
Relative humidity
The amount of water vapor in a volume of air relative to the amount of water vapor needed for that volume of air to reach saturation is called relative humidity.
RH = water vapor content /water vapor capacity X100%

18. Humidity Relative humidity
Section 11.2
Properties of the Atmosphere
Humidity
Relative humidity
The dew point is the temperature to which air must be cooled at constant pressure to reach saturation.
(RH = 100%)

19. Section 11.2
Properties of the Atmosphere
The extra thermal energy contained in water vapor compared to liquid water is called latent heat.

20. Change of state diagram.

21. Humidity Condensation level
Section 11.2
Properties of the Atmosphere
Humidity
Condensation level
A process in which temperature changes without the addition or removal of thermal energy from a system is called an adiabatic process.
Adiabatic heating occurs when air is compressed, and adiabatic cooling occurs when air expands.

22. Humidity Condensation level
Section 11.2
Properties of the Atmosphere
Humidity
Condensation level
Condensation occurs at the lifted condensation level (LCL). Air above the LCL is saturated and thus cools more slowly than air below the LCL.

23. 11
Study Guide
Key Concepts
Section 11.2 Properties of the Atmosphere
Atmospheric properties, such as temperature, air pressure, and humidity describe weather conditions.
At the same pressure, warmer air is less dense than cooler air.
Air moves from regions of high pressure to regions of low pressure.

24. 11
Study Guide
Key Concepts
Section 11.2 Properties of the Atmosphere
The dew point of air depends on the amount of water vapor the air contains.
Latent heat is released when water vapor condenses and when water freezes.

25. 11
Atmosphere
11.2 Section Questions
What is the relative humidity of a parcel of air that has reached its dew point?
a. 25 percent
b. 50 percent
c. 75 percent
d. 100 percent

26. 11
Atmosphere
11.2 Section Questions
A sealed container holds only air. If the temperature of the air inside the container is increased, which other property of the air also increases?
a. volume
b. density
c. pressure
d. mass

27. 11
Atmosphere
11.2 Section Questions
During which changes of state does water release latent heat?
a. condensing and freezing
b. evaporating and melting
c. evaporating and freezing
d. condensing and melting