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Objectives for Chapter 11 –PART #2:
Water in the Atmosphere: Clouds, Humidity, Water Cycle
1. I can explain how clouds are formed. This means I can:
A. List the 3 requirements for cloud formation, describe why they are needed and how they interact.
B. Describe explain the 2 main lift mechanisms that drive air upward and facilitate cloud formation.
C. Explain how cloud formation is related to atmosphere stability.
D. Compare & contrast humidity and relative humidity.
E. Explain the concept of dew point and relate it to cloud formation.
2. I can identify the basic characteristics of different cloud groups. This means that I can:
A. Define the following Latin words or prefixes and tell how they are related to cloud classification: cirro, alto,
strato, cirrus, cumulus, stratus, nimbus.
B. Classify, identify and label pictures of clouds into basic categories using the terms in Objective 2A.
C. Compare and contrast the 2 types of fog, identify the fog cloud type and explain how fog occurs.
3. I can determine the relative humidity in the following 2 ways. I can:
1. Use a sling psychrometer and its data table to determine the relative humidity of air.
2. Calculate the relative humidity if given the humidity and the water vapor capacity of a given air parcel.
4. I can compare and contrast various phase changes, including whether heat energy is absorbed or released.
5. I can describe the water cycle using the following terms and describe their interrelationships: evaporation,
condensation, collision-coalescence, and precipitation.
6. I can define and use the following miscellaneous terms: heat, dew point, saturation, condensation, lifted
condensation level (LCL), humidity, relative humidity, condensation nuclei, orographic lifting, frontal wedging, stable
atmosphere, unstable atmosphere, latent heat, collision-coalescence.
Dew Point, Lifted Condensation Level, Wind & Humidity
1. Dew Point = Temperature to which air must be cooled to reach saturation (until it can hold no more water)
A. __________________________: The point where air holds as much water vapor as it can
B. At this point water will ____________________________________
C. ________________________________ is when matter changes state from a gas to a liquid
D. Dew Point is AKA “Condensation Point”
E. NOTE:
Dew ≠ rain
&
Cloud condensation ≠ rain
2. Vertical Temperature Changes
A. In the troposphere, temperature ____________________ with altitude
B. Warm air rises until it reaches cooler atmosphere with the temperature of its dew point(condensation point)
C. Lifted Condensation Level (LCL) is the height where __________________________________
i.
ii.
iii.
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It is level with the bottom of clouds.
Clouds form when water vapor condenses
See Fig. 11-8, p. 279
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3. Humidity vs. Relative Humidity
A. Humidity is the ACTUAL amount of ____________________ in the air
B. Relative humidity is a ratio comparing the humidity (ACTUAL amount) to how much water vapor a parcel of
air is CAPABLE of ____________________________

What is a parcel of air? Think of a balloon, or air at a certain location at a certain time/day/temperature
i.
Warm air can hold ______________ water
ii.
Cold air is capable of holding ___________water
iii.
Relative humidity is expressed as percentage
 ___________ relative humidity = saturation
 Equation: Relative Humidity = Actual Humidity / Capacity x 100%
iv.
Relative humidity percentage affects the probability of cloud formation & precipitation
Cloud Formation
Cloud Formation: Requires 3 things: ***water vapor, ***condensation nuclei & ***a lifting mechanism
1. Water vapor
A. Clouds form when moist warm air rises, then cools & condenses at the LCL
B. ____________________is the tendency to rise or sink due to _________________________
2. Condensation Nuclei are small particles in the atmosphere that ___________________ condense on
i.
Examples: Dust, salt, smoke particles
ii.
As air reaches area with temperature of its dew point, water vapor condense on the__________
3. Lift mechanisms:
 Warm, moist air does expand and rise, but to quickly form clouds, the warm, moist air must be forced
upward faster than convection can carry it.
 **There are 2 main Lift Mechanisms :
1. 1st Method: Orographic lifting = Lifting when wind encounters a __________________ and has
nowhere to go but up
A. Mountain is ____________________ so the air rises over
B. Air rises until it hits condensation temperature at the LCL & clouds form
2. 2nd Method: Frontal Wedging = Lifting when two air masses of different temperatures collide
A. Cold air is very _____________, therefore the warm air is forced ____ .
B. Warmer mass (less dense) rises. Clouds form when the warm air reaches
its__________________ temperature at its ______________
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Types of Clouds
1. Cloud Classification
A. Based on 2 things: Height in Atmosphere & Shape
i.
ii.
iii.
See Table 11-3 pg. 287 for Cloud Classification
See Figure 11-14 pg. 288 for cloud pictures
Know the Latin meanings and recognize drawings/pictures of the clouds
2. Height Descriptions = Prefixes
A. Cirro = _______________ in the troposphere. Made of ___________ crystals
B. Alto = _______________ . All liquid or a mixture of _____________________________
C. Strato = ______________ in the troposphere. All liquid.
3. Shape Descriptions = 2nd part (Main Part) of Name
A. Cirrus – ___________________. Very high. Looks stringy, wispy, curled up at end. “Like hair”.
B. Cumulus = __________________. Looks like cotton balls or popcorn.
C. Stratus = ___________________. Continuous cloud. Looks like a sheet or blanket.
Stratus = “stretched” or sheet
4. Special Cloud s & Terms
A. Nimbus = _______________________ Looks like it will rain. What would a nimbostratus cloud look
like? ___________________________
B. Cumulonimbus
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i.
It is a special storm cloud AKA __________________________
ii.
It is a “Vertical Development Cloud”. Develops and reaches
through all altitudes from low to high in the troposphere.
iii.
Top has _________ crystals
iv.
Strong ______________give the top an anvil shape
v.
Capable of strong __________ and _____________,
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C. Fog = _______________cloud that forms when dew point of water vapor is reached close to Earth’s
surface
 There are many mechanisms that can cause fog. Following are the 2 mechanisms we’ll discuss
in class that can cause this cooling close to ground:
1. Radiation Fog – occurs on cool/clear/calm nights
 Type of fog here in Iowa

______________________ from earth’s surface is lost to space with ________________

Cool surface means cool air above it.

Cool air _________ hold as much water vapor & becomes ________________.

Depth of fog is the height to which air temp has dropped to its _________________.

Radiation Fog is ______________________________

Fog dissipates (goes away) quickly when sun comes up. Why? ___________________
2. Advection Fog – Moist warm ocean air moves over cold land

What part of the U.S. frequently experiences this type of fog? __________________

NOT caused by a decrease in surface temperature like radiation fog, but by MOVEMENT
over a cold surface
Big water bodies (oceans) don’t lose heat as fast as land at night, so the moist air above
the water stays warmer at night.


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Water vapor condenses as it _________________ colder land, losing the heat energy in
the air to the cold land surface. (Advection Fog is NOT stationary)
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Can you identify the type of this cloud? :
Of the following, which describes a layered cloud that is dense enough to block out the Sun & is composed
entirely of ice crystals?
A. Stratus
B. Cirrostratus
C. Altostratus
D. Clouds of vertical development
Air Stability & Latent Heat
Stability: Is the ability of an air mass __________
1. All rising air expands and cools
2. The _________________________at
which a parcel of air rises & cools
determines its stability
3. Speed of rising depends on the
____________________________ in air
temperature near the ground to the
upper troposphere
http://www.cssforum.com.pk/attachments/css-optional-subjects/groupd/geography/3391d1280601535-diagrams-related-physical-geographyimage002.jpg
4. Stable Atmosphere: High stability = little rising
A. Air at surface is _____________ & _________________________,resulting in little to no rising.
B. Clouds are _____________________________
5.
Unstable Atmosphere: (Instability)
A. Air at the surface is ______________with ____________density.
B. The temperature quickly ________________________ with altitude.
C. The resulting rapid rise (instability) can produce ____________________and intense ____________
D. Increased speed of rising & instability can be due to:
i. Temperature gradient as discussed above
ii. Increased further by a high amount of _________________________ in the rising air.


Lots of _____________________________at the LCL will release “latent heat”.
This heat continues to warm atmosphere, air continues to rise, cloud continues to grow.
iii. Warm air forced quickly up the face of a _______________air mass(front)
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Latent heat the energy absorbed by or released from a substance during a phase change from a gas to a liquid or a solid
or vice versa
1. Evaporation: For liquid water to change to vapor, energy must be _______________________________

Energy is needed to spread out the molecules into the less dense vapor (gas)

Example: you must__________________ water to cause boiling and evaporation
2. The absorbed (added) energy is _____________________in the ___________________
3. Condensation & Cloud Formation: Latent Heat energy is __________________when condensation occurs

Condensation = Phase change from _______________________ to _____________water

For molecules to slow down and come closer together, latent heat energy is released (given off)
during condensation
This released heat energy warms the atmosphere around the forming cloud, causing air to
continue to rise.
If lots of condensation & cloud formation occur, the latent heat energy heats the atmosphere &
causes it to be more _________________________.


Precipitation
1. Includes all forms of water, both liquid and solid, that fall from the sky
A. Rain, snow, sleet, hail, etc.
B. Caused by _____________________________: the formation of larger droplets as small clouds droplets
collide and ________________together
C. Droplet finally becomes ______________________ and gravity pulls it to Earth as precipitation.
The Water Cycle
1. Is the constant movement of water between the __________________________ and Earth’s surface
2. The total amount of water on Earth has been constant for millions of years:
A. _________ salt water
B. _________ fresh water, and 2/3 of fresh water is frozen in the polar ice caps
Steps of the Water Cycle
1. Step 1: Evaporation: Adds water to atmosphere through the process of changing from _____________
A. What is Evapotranspiration? ____________________________________________
2. Step 2: Condensation: Cloud formation due to ________________________________
3. Step 3: Precipitation: Returns to earth’s surface
4. The Cycle then ___________________________
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Study Tips
• Textbook reading
1. Objectives at the beginning of this note outline and of each textbook section
2. Vocab words: italicized at the beginning of each section, and bold throughout text
3. Questions at the end of each section and at the end of the chapter
4. Summary page at end of chapter
• Notes, labs and worksheets from class
• Class Webpage. Links to:
1. Videos on topics in the unit.
2. Quizlet website for vocabulary review, flashcards, games and quizzes
3. Textbook website with practice quizzes for each chapter
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