Name __________key______________
Mrs. G-M (200 Earth)
Date _______
Period ______
Ch. 18 Moisture, Clouds, & Precipitation REVIEW for Quiz
1. Which gas is most important in understanding atmospheric processes (ex.
weather)?
 water vapor
2. What is "humidity"?
 the general term for the amount of water vapor in the air (two types
absolute/specific & relative)
3. What is "water vapor capacity"?
 the amount of water air can "hold" at a given temperature
4. How does temperature affect the amount of water vapor needed to saturate the
air (...to reach water vapor capacity)?
 Warm air can hold more water than cold air (It takes more water vapor to
saturate warm air.)
 Cold air can hold less water than warm air (It takes less water vapor to
saturate cold air.)
5. What is "specific (absolute) humidity"?
 the ACTUAL amount of water vapor in the air (for a given time & place)
6. How do we express specific (absolute) humidity?
 specific humidity = mass of water vapor (g)
1 kg of air
7. What is "relative humidity (RH)"?
 RATIO of how close air is to maximum water vapor capacity (HOW "FULL" of
water vapor the air is)
Name __________key______________
Mrs. G-M (200 Earth)
Date _______
Period ______
8. How do we express relative humidity (RH)?
 relative humidity =
specific humidity
X 100
maximum vapor capacity
9. What is the approximate relative humidity of each container?

10.
A = 50%, B = 25%, C = 50%
What are the two ways that relative humidity (RH) can be changed?
 adding/removing water vapor
 changing the air temperature
11. How does air temperature affect relative humidity (RH)?
 inverse relationship
o as air temp goes down, RH goes up (b/c colder air can hold less
water/decrease capacity)
o as air temp goes up, RH goes down (b/c warmer air can hold more
water/increase capacity)
12.
The air is ____saturated_________ when it has reached 100% relative
humidity (RH) and the air is "full" of water vapor (...has reached its water vapor
capacity).
13.
What is the special name for the temperature at which saturation (100%
relative humidity) occurs?
 dew point temperature
14.
What happens when the air has reached the dew point temperature?
 condensation (gas/vapor turns to liquid) (& often precipitation)
Name __________key______________
Mrs. G-M (200 Earth)
15.
Date _______
Period ______
How does air temperature affect saturation?
 It takes more water vapor to saturate warm air b/c higher water vapor
capacity of warm air... and less water vapor to saturate cold air b/c lower
water vapor capacity of cold air
16.
What are the steps used to determine relative humidity using a sling
psychrometer (along w/ Ref. Tbls.)?
 Using a sling psychrometer:
o 1. Wet the wick on the wet bulb.
o 2. Spin the psychrometer for the specified amount of time.
o 3. Read temperatures on both the wet & dry bulbs. (Wet bulb temp. should
always be equal to or cooler than the dry bulb temp. due to the evaporation
of the water.)
o 4. Record your data.
 Using the RH chart
o 1. Calculate difference between wet & dry bulb temperatures
o 2. Locate difference on the (top of) RH chart
o 3. Locate dry bulb temp. on the (left of) RH chart
o 4. Where they intersect gives the RH (in %)
17.
What is the relative humidity if the dry-bulb temperature on the sling
psychrometer is 10° C and the wet-bulb temperature is 8° C? (difference = 2° C)
 76%
18.
What are the steps used to determine the dew point (temperature) using a
sling psychrometer (along with your reference tables)?
 same method as finding relative humidity (RH)... see #16... EXCEPT use dew
point chart on Ref. Tbls.
Name __________key______________
Mrs. G-M (200 Earth)
19.
Date _______
Period ______
What is the dew point (temperature) if the dry-bulb temperature on the sling
psychrometer is 10° C and the wet-bulb temperature is 8° C? (difference = 2° C)
 6° C
20.
Where in the atmosphere can clouds form? Why?
 anywhere in troposphere b/c only atmospheric layer w/ water vapor
21.
What two things make up clouds?
 water (liquid or ice) & condensation nuclei
22.
In general, how do clouds form?
 air rises, cools, reaches dew point, condenses (gas --> liquid) or undergoes
deposition (gas --> solid), & cloud forms (LIQUID water droplets or solid
water/ice crystals NOT gas/water vapor)
23.
What is the name for the atmospheric level where condensation occurs?
 condensation level
24.
What is the "orographic effect"?
 rainfall that results from the "lifting" of air over mountains
25.
What is the "windward" side of the mountain? What happens there?
 moist air blows toward mountain, is forced up mountain/rises, air expands &
cools (due to molecules moving apart), air reaches dew point & clouds
form/precipitation occurs (...wet on the windward side)
26.
What is the "leeward" side of the mountain? What happens there?
 air is now dry & cool at top of mountain, as air is leaving mountain it sinks
(b/c dry air is more dense) & warms (due to molecules getting closer), due
to drier/warmer air there are generally no clouds or precipitation & a "rain
shadow desert" forms (...leeward side of the mtn, was as dry as it could be)
Name __________key______________
Mrs. G-M (200 Earth)
27.
Date _______
Period ______
What happens during "frontal wedging"?
 masses of warm & cold air collide producing a front --> the warmer, less
dense air rises over the cooler more dense air (often resulting in clouds &
precipitation)
28.
What happens during the "convergence" of air?
 air flows horizontally, collides, gets pushed upward (often resulting in clouds
& precipitation)
29.
What is "localized convective lifting"?
 air is warmed more than surrounding air (usually due to heating of surface
below), becomes less dense, & rises (often resulting in clouds &
precipitation)
30.
What causes condensation?
 as air is cooled, water vapor capacity decreases (causing relative humidity to
increase)... when air reaches the dew point temperature, the air becomes
saturated (& RH = 100%) condensation occurs (gas/vapor --> liquid)
31.
What "features" form/what are the effects when air reaches the dew point
temperature and the air becomes saturated?
 dew, clouds, fog, precipitation
32.
What are "condensation nuclei"? Why are they needed for clouds to form?
 material needed for water vapor to condense onto (ex. dust, sand, salt,
aerosol particles)
33.
Clouds are classified according to ______shape______ & ____altitude_____.
Name __________key______________
Mrs. G-M (200 Earth)
34.
Date _______
Period ______
"Stratus" or "strato-" means that clouds have a ______layered____ shape or
appearance.
35.
"Cumulus" or "cumulo-" means that clouds have a _____puffy, heaped______
shape or appearance.
36.
Stratus, nimbostratus, cumulus, and stratocumulus are ______low_________
altitude clouds.
37.
Altostratus and altocumulus are ________middle_________ altitude clouds.
38.
"Cirrus" or "cirro-" indicate ____high_____ altitude clouds (such as cirrus,
cirrostratus, or cirrocumulus).
39.
"Nimbus" or "nimbo-" indicates ___dark, rain/storm_____ clouds (such as
nimbostratus or cumulonimbus).
40.
What is "precipitation"?
 any form of water that falls to Earth from a cloud
41.
What are examples of precipitation?
 drizzle, rain, glaze/freezing rain, snow, sleet, hail
42.
How is precipitation measured?
 measured to the hundredth of an inch (2 decimal places)
43.
What instruments are used to measure precipitation?
 rain = rain gauge
 snow = measuring stick