Pages 478-479: Unit 7 Review
2. Humidity-relative humidity
 Humidity is a measure of the amount of water vapor present in the air. Can be given in units
of g/kg or g/m3.
 Relative humidity is a comparison of the amount of water vapor present in the air to the
amount needed for saturation to occur. Is given in units of %. Both humidity and
temperature can influence relative humidity.
3. Relative humidity-dew point


Relative humidity is a comparison of the amount of water vapor present in the air to the
amount needed for saturation to occur. Is given in units of %. Both humidity and
temperature can influence relative humidity.
Dew point is the temperature at which an air mass is saturated with water vapor (holding the
maximum amount). It is given in units of temperature (degrees F or degrees C). Air has to
be cooled to the dew point in order for condensation to occur. The relative humidity at the
dew point is always 100%.
4. Dew point- precipitation


Dew point is the temperature at which an air mass is saturated with water vapor (holding the
maximum amount). It is given in units of temperature (degrees F or degrees C). Air has to
be cooled to the dew point in order for condensation to occur. The relative humidity at the
dew point is always 100%.
Precipitation is water falling from clouds. Can be in the form of liquid or solid water.
9. isobar-isotherm
Both are isolines- lines that show equal values on a weather map.
 Isobars are lines of equal pressure
 Isotherms are lines of equal temperature
11. Which term refers to the amount of water vapor in the air?
c- humidity
13. Which type of air has a RH that of 100%
d- saturated
14. Which type of the following clouds are high feathery clouds made of ice crystals?
a. cirrus
15. What is a large body of air that has the same properties as the area over which it formed called?
a. air mass
16. At what temperature does water vapor in air condense
a. dew point
17. Which type of precipitation forms when water vapor changes directly into a solid
d. snow
18. Which type of front may form when cool air, cold air and warm air meet?
d. occluded- Happens when a cold front catches up to a warm front (see page 464 in your book)
19. Which is issued when severe weather conditions exist and immediate action should be taken?
d. warning
20. What is a large, swirling storm that forms over warm, tropical water called?
a. hurricane
21. Explain the relationship between temperature and relative humidity.
If humidity is kept constant (the amount of water vapor in the air DOES NOT change) then:
-If temperature increases, the relative humidity will decrease. This is because warmer air needs
more water vapor in order to reach saturation.
-If temperature decreases, the relative humidity will increase. This is because cooler air needs less
water vapor in order to reach saturation.
24. What does it mean if the relative humidity is 79%?
This means that the air is currently holding 79% of the maximum amount of water vapor it can hold
(its saturation value).
26. Compare and contrast the weather conditions at a cold front and the weather at a warm front.
Both produce clouds and precipitation.
Cold front- high winds, large cumulonimbus clouds, brief showers/thunderstorms, dropping
temperatures
Warm front- extended precipitation events (hours), nimbostratus clouds, rising temperatures
30. You take a hot shower. The mirror in the bathroom fogs up. Infer from this information what
has happened.
The water vapor in the air due to your shower has condensed on the cooler surface of the mirror.
The mirror needs to be at or below the dew point.
33. If the air temp is 25 degrees C and the relative humidity is 55%, will the dew point be reached if
the temperature drops to 20 degrees C.
Need to use the information on the chart.
First have to figure out how much water vapor is actually in the air. You know that it is currently
holding 55% of what it can hold. You need to determine what 55% of 22 g/m3 is. Multiply 22 * .55
to find that 55% of 22 is 12.1. By looking at the chart you see that at 20 degrees C, the air has a
saturation value of 15 g/m3. Therefore the dew point would not be reached at 20 degrees, because
you would still be holding less than the maximum amount of water vapor possible.
34. If the air temp is 30 degrees C and the RH is 60%, will the dew point be reached if the
temperature rises to 35 degrees C.
No, because the air would be able to hold MORE water vapor at a higher temperature. Therefore the
RH would drop. An RH of 100% is needed at the dew point.
Heath Book page 521
Critical Thinking 1-4
Temp degrees C
16
20
20
28
28
DP degrees C
12
12
16
12
20
Condensation level
500 m
1000 m
500 m
2000 m
1000 m
*these are all based on the second line of the chart. That information showed that it takes 1000 m
for this air mass to cool 8 degrees
1. This would make the cloud base higher because the temperature would have to cool more.
2. If the temperature is constant, but the dew point rises, the cloud base would be lower. The air
wouldn’t have to cool as much.
3. 50% RH at 26.5 degrees C would have more water vapor than saturated air at 5 degrees C. This
is because warmer air has a higher capacity for water vapor.
4. At warmer temperatures, there would be less temperature change with height. At very cold
temps, the air holds little water vapor and the moist adiabatic lapse rate approaches the dry adiabatic
lapse rate.
Pg 571
Procedure
2.
City
Indianapolis
Louisville
Chattanooga
DP
43
52
59
Temp
52
64
64
3. A- cold, moving east
B. warm, moving North
C. occluded, was moving North to Northeast
1. Low pressure is moving air counterclockwise. It spirals the cold front into the warm front to
create an occluded front.
2. The dew point increases from N to S.
Warm moist air is coming from the South.
3. Warm front has passed over leaving warm air behind. Winds are coming from the South
where it is warmest.
4. Fast uprising of warm moist air ahead of the front causes thunderstorms.
5. Memphis has the highest winds because it is right at the cold front.