1. Moisture in the Air

2. Changes in States (Phases):
s  l Freezing and melting l   g Condensation and evaporation s  g Sublimation Latent heat: heat energy ‘trapped’ in a state of matter calories g
Heat absorbed! l
Heat Released! s

3. Examples of:
Condensation: dew, clouds, fog, drops on surfaces Evaporation: “drying off” Sublimation: snow disappearing, dry ice, frost

4. Sublimation Wind Condensation Precipitation Transpiration Runoff
Releases Heat
Precipitation
Transpiration
Runoff
Evaporation
Absorbs Heat
Respiration
Groundwater
Aquifer

5. Moisture in the Air-Humidity
What is humidity?
Humidity is the moisture in the air.
“Think of air like a sponge.”
2. Relative Humidity is the amount of moisture in the air compared to how much moisture that air could possibly hold at a certain temperature.
Specific humidity vs. capacity.
Expressed in %

6. 3. Air at a certain temperature can hold only so much water
3. Air at a certain temperature can hold only so much water. See chart on page 501. a/ Warmer air can hold more water vapor. Air at 86F can hold 30 g b/ Colder air can hold less water vapor. Air at 32F can only hold 5 g

8. 4. When air cools and its ability to hold water decreases it becomes saturated and condensation occurs. This occurs at 100% relative humidity. 5. The temperature at which water condenses out of the air is called the dew point temperature.

9. 6. Relative Humidity Calculations:
Amount of moisture in air (Specific humidity) x 100 = % RH
Amount possible at temperature (capacity)
Relative Humidity Problems: Find the RH of the air.
1/ Air at 86oF contains 15g of moisture but can only hold 30g. What is the RH?
2/ Air at 68oF contains 12g of moisture but can only hold 16g. What is the RH?
3/ Air at 68 oF contains 16g of moisture and can only hold 16g. What is the RH?

10. 6. Relative Humidity Calculations:
Amount of moisture in air (Specific humidity) x 100 = % RH
Amount possible at temperature (capacity)
Relative Humidity Problems: Find the RH of the air.
1/ Air at 86oF contains 15g of moisture but can only hold 30g. What is the RH?
2/ Air at 68oF contains 12g of moisture but can only hold 16g. What is the RH?
3/ Air at 68 oF contains 16g of moisture and can only hold 16g. What is the RH?
15g x 100 =
30g
50% RH
12g x 100 =
16g
75% RH
16g x 100 =
16g
100% RH Dew point Temp

11. 7. Meteorologists use a Hygrometer(hair) or a Psychrometer (dry-wet bulb thermometer) to measure Relative humidity.

12. 8. Rising Air masses and Relative humidity: Condensation and Dew Point
An air mass which contains 7g of water vapor/ft3 rises into the upper troposphere. Calculate the RH of the air mass at each step shown. The amount of moisture that air can hold at a certain temperature is called the capacity (saturation point). It is shown in the table below:
Temperature
Capacity(saturated)
86oF
30.4g
68 oF
17.3g
60 oF
13.5g
50 oF
9.41g
40 oF
7.2g
32 oF
4.85g
Temperature Specific Humidity Capacity %RH
oF g ? = ______%
oF g ? = ______%
oF g ? = ______%
oF g ? = ______%
5. At level 4.
6. Clouds-condensation (reaches dew point temperature).

13. 8. Rising Air masses and Relative humidity: Condensation and Dew Point
An air mass which contains 7g of water vapor/ft3 rises into the upper troposphere. Calculate the RH of the air mass at each step shown. The amount of moisture that air can hold at a certain temperature is called the capacity (saturation point). It is shown in the table below:
Temperature
Capacity(saturated)
86oF
30.4g
68 oF
17.3g
60 oF
13.5g
50 oF
9.41g
40 oF
7.2g
32 oF
4.85g
Temperature Specific Humidity Capacity %RH
oF g = %
oF g = %
oF g = %
oF g = %
5. At level 4.
6. Clouds-condensation (reaches dew point temperature).

14. What is humidity? 7. Meteorologists use a Hygrometer(hair) or a
Psychrometer (dry-wet bulb thermometer) to measure Relative humidity.
1st Find dry bulb and wet bulb temperatures after rotating psychrometer through the air.
2nd Calculate the difference between the dry and wet bulb temperatures. (subtract).
3rd Use chart on p501 to determine the relative humidity.

15. Dry Bulb Temp.
Wet Bulb Temp.
Difference
% Rel. Humidity
20 C
16 C
14 C
11 C
15 C
12 C
18 C
18 C
13 C
8 C
14 C
13 C
17 C
15 C

16. D. Clouds 1. Cloud Formation
a. Warm moist air is lighter than cold dry air. Warm moist air rises.
b. Warmer air holds more water vapor than colder air.
c. As you increase altitude temperatures decrease and it gets
colder. Warmer air holds more water vapor.
d. As warm moist air rises and it gets colder it can hold less water
vapor and relative humidity increases.
e. Eventually, the rising air mass gets to a colder temperature
where the relative humidity reaches 100% and the air becomes
completely saturated. This temperature is called the dew point
temperature.
f. This is when condensation occurs and water droplets come out
of the air as clouds.

17. D. Clouds
1. Cloud Formation
Warm moist air is lighter than cold dry air.
Warm moist air rises.
b. Warmer air holds more water vapor than colder air.
c. As you increase altitude temperatures decrease and it gets colder. Warmer air holds more water vapor.

18. d. As warm moist air rises and it gets colder it
d. As warm moist air rises and it gets colder it can hold less water vapor and relative humidity increases.
e. Eventually, the rising air mass gets to a colder temperature where the relative humidity reaches 100% and the air becomes
completely saturated. This temperature is called the dew point temperature.
f. This is when condensation occurs and water droplets come out of the air as clouds.

19. 2. The ingredients of a cloud are: 1/ Air 2/ Water vapor
3/ Change in T or P
4/ Condensation nucleii - dust

20. 1/ Cumulus (Cu) Puffy, rising air, 2/ Stratus (St) layered, low
3. Cloud Types and Names (The Classification of Clouds):
Three Main Types of Clouds are:
1/ Cumulus (Cu) Puffy, rising air,
2/ Stratus (St) layered, low
3/ Cirrus (Ci) feathery, high, ice

21. Prefixes/suffixes used to further describe cloud types are:
1/ Alto- (A) middle level
2/ Nimbus- (N) rain
3/ cumulo- (Cu)
4/ Cirro- (Ci)

22. Nimbostratus
Cirrocumulos
Altostratus
Cirrus
Altocumulus
Cumulonimbus
Cumulos

23. E. The Four Types of Precipitation are:
1/ Rain
2/ Snow
3/ Sleet-frozen rain
4/ Hail- from cumulonimbus clouds!
Moisture 6
snow
snow
snow
rain
snow
sleet
rain