Humidity and Air Pressure Study guide
Review your notes, textbook, and labs.
Relative Humidity & Dew Point- review relative humidity lab
1.What is humidity?________The amount of water vapor in the atmopshere._________________________
2.What is relative humidity?__The amount of water vapor in the atmosphere compared to how much the atmosphere
can hold at that temperature (% of how saturated or unsaturated the air is)__
3.What is the dew point?__The temperature that condensation will occur at a certain relative humidity.____
4. For condensation to occur the dry bulb temperature has to be equal to the dew point. (circle all that are true)
5. As the wet bulb depression decreases, the relative humidity increases (use the chart)
6. If the wet bulb depression is zero than the wet bulb is equal to the dry bulb
7. When the dry bulb and wet bulb are equal relative humidity is 100% .
8. When the dry bulb and wet bulb are equal the dry bulb temperature is also the dew point. What will happen?
___condensation___
9. When air gets cooled, it can hold
less
water vapor than warmer air.
10. When the dew point = dry bulb = wet bulb:
What is the relative humidity?__100%______ wet bulb depression?___0 Celsius____
If the dew point is above 0 Celsius what kind of precipitation will occur?___rain_____________________
If the dew point is below 0 Celsius what kind of precipitation will occur?___snow_____________________
11. Use the charts on the class web page.
City
Dry Bulb
C
Wet Bulb
C
Wet Bulb
Depression C
Relative
Humidity %
Dew
Point C
Will it rain, snow, or does the temperature need
to drop? How much does it need to drop?
Shobcago
-1
-6
5
8
-9
From -1 to -9 = 8 C drop before
condensation can happen
Shobe Francisco
7
Between In between
2&1
5 & 6….5.5
38 to 26….
0
7-0 = 7 It must drop 7 C to reach the dew
point so condensation can occur
15
Rain
32
1.5
East Shobwick
15
15
0
100
dry=wet=dew point which is above 0C
Shobington DC
14
10
4
60
11
14-11 = 3 degrees. It needs to drop 3 C
before condensation can occur
Shobe Angeles
-3
-3
0
100
-3
Snow
dry=wet=dew point which is above 0C
12. What is a psychrometer and how does it work?
__2 thermometers. One dry (tells the temperature of the air) and one wet (it will evaporate and show a lower
temperature). One can then calculate the difference between these 2 bulbs (the depression) and using a chart can
determine the relative humidity and dew point.)___
Clouds-review cloud lab
13. Match the cloud types.
Word bank: cirrus, cumulus, cumulonimbus, nimbostratus, stratus
a. Low altitude flat layers they are ___stratus______________________
b. Wispy, curly, made of ice crystals and at high altitudes they are ____cirrus___________________
c. Puffy cottony piles they are __cumulus___________________________
d. Puffy clouds that produce rain___cumulonimbus__________________________
e. Flat clouds that produce rain_____nimbostratus________________________
14. What stage of the water cycle produces clouds?____condensation______________________________
15. What is condensation?___when gases become liquids._________________
16. How do clouds form? What ingredients are needed?
__When water vapor cools and condenses around condensation nuclei. Water vapor, aerosols, and cool air______
Air Pressure- review pressure demos
17. Complete the table below
Rise or
Sink
Clockwise or
counterclockwise
Cyclonic or Warm or
anticyclonic cool
Moist or
Dry
High or low
numbers
What kind
of weather
High
Pressure
sink
clockwise
anticyclonic cool
dry
high
Fair
Low Pressure
rise
(happy)
counterclockwise
cyclonic
warm
moist
low
Rainy
(lousy)
18. What is air pressure?___pressure exerted by gasses. Denser air equals higher pressure.___________
19. What are 2 instruments used to measure pressure?__mercury barometer______ & ___aneroid barmometer__
20. Be able to read these instruments and identify them in a picture.
21. On a mercury barometer what are the units for the following measurements:
996___mm of mercury______
30.5____inches of mercury__
22. What happens to pressure with elevation?__decreases__________________________________
Isotherms and Isobars- review the packet on isobars
23. Be able to draw isotherms/isobars. Which shows temperature?___isotherms________Pressure?____Isobars___
24. Determine where low pressure and high pressure centers are and what kind of weather there will be.
25. Will wind blow from high to low pressure OR low to high pressure?_____high to low___________________
Air Masses
26. Complete the table below:
Type of air mass
Where it forms
(land or ocean)
Humidity
(moist or dry)
Temperature
(warmer or colder)
Maritime Polar (mP)
ocean
moist
colder
Maritime Tropical (mT)
ocean
moist
warmer
Continental Polar (cP)
land
dry
colder
Continental Tropical (cT)
land
dry
warmer
Fronts- review fronts demonstration
27. What is a front?____the location where 2 air masses meet_______________________________
28. Does weather change at a front or within an air mass?___at a front________________
29. Why do cold air masses flow underneath warm air masses?___cold air is denser than warm air________
30. Complete the table below:
A front is a boundary between air masses with different properties (like temperature, moisture, pressure, wind
direction, etc). The type of front is determined by which air mass is advancing: e.g., cold front = cold air
advancing.
There are four types of fronts (pictured below) 



stationary front (no movement of either air mass)
cold front (cold air advancing)
warm front (warm air advancing)
occluded front (cold front overtakes the warm front - signals the weakening phase of a midlatitude cyclone).
Front type
Drawing
Symbol
Weather
(point in the direction the air
mass is moving)
Warm
Long storms
Both move in the
same direction.
Warm air does the
pushing and over
takes the cold.
cold
Severe short storms
Both move in same
direction. Cold does
the pushing and
overtakes the warm.
Stationary
Move in opposite
directions pushing
into each other. No
movement for a
while.
Occluded
cold front catches
up to and overtakes
a warm and pushes
it up so that none of
the warm air mass
is in contact with
the ground
Clear to partially
cloudy
Wide spread
cloudiness and rain