Download - 2-3 Moisture Precipitation Clouds PPT LESSON
Do You Remember?1. Which heats faster: land or
water?2. What causes the transfer of
energy (heat) from one object to another?
3. Which has greater temperature variation: land or water?
Moisture, Clouds and Precipitation2.5.4c Explain the importance of water vapor and its influence on weather (clouds, relative humidity, dew point, precipitation).
ObjectivesToday I will be able to:
◦Evaluate the most important gas in the atmosphere.
◦Compare and contrast saturation and relative humidity.
Key Points - MoistureWater vapor is the most important gas for
understanding atmospheric processes.Water vapor makes up 0-4 % of atmospheric
gases.Air that has reached its water vapor capacity
is said to be saturated.Warm, saturated air contains more water
vapor than cold air.Relative humidity is the ratio of air’s water-
vapor content to its capacity to hold water vapor at that same temperature.
Water in the AtmosphereWater exists in three different
forms.What are they?
1. SOLID Examples: Snow, ice2. LIQUID Examples: Rain, water3. GAS Examples: Clouds, water vapor
How do each of these forms of water influence weather?
Water in the Atmosphere When it comes to understanding
atmospheric processes, water vapor is the most important gas in the atmosphere.
Why do you think water vapor is so important?
Water in the AtmosphereEven though water vapor is
important, it only makes up from 0 – 4% of the atmospheric gases.
When have you felt water vapor at close to 4%?
What about 0%?How do you know?
◦Water vapor is the HUMIDITY that you feel in the air!
Water in the AtmosphereWhat do you think the word
“SATURATED” means?What do you think it would mean
if air is Saturated?Air that has reached its water
vapor capacity is said to be saturated.
Water in the AtmosphereWarm, saturated air contains
more water vapor than cold air.Dew point is the temperature to
which air is cooled to reach saturation.◦The point at which condensation can
occurWhen have you noticed the
humidity more, in the summer or in the winter?
That’s because warm air can hold more water vapor!
Water in the AtmosphereRelative humidity is the ratio of air’s
water-vapor content to its capacity to hold water vapor at that same temperature.
Relative humidity indicates how near the air is to saturation, not the actual quantity of water vapor in the air.
Relative Humidity varies with temperature.
Cooling air increases its relative humidity.Warming air decreases its relative
humidity.
Water in the AtmosphereRelative Humidity – Why does lowering the air temperature cause
Relative humidity to increase?◦Because colder air cannot hold as much water
vapor!Why does increasing air temperature cause
relative humidity to decrease?◦Because warm air can hold more water vapor and
it will take more water vapor for it to become saturated.
◦Why is it important to know humidity?
Vocabulary and QuestionsDefine the following terms:Water vaporSaturationRelative humidity
Answer the following questions:1. What gas is most important for understanding
atmospheric processes?2. Water vapor makes up what fraction of
atmospheric gases?3. Which holds more water vapor: warm air or cool
air?4. How is the humidity different from the
summertime to the wintertime?
Matching- answer a, b or c for each of the situations.Situation1.Water vapor is
added2.Air temperature
decreases3.Water vapor is
removed4.Air temperature
increases
Change in Relative Humidity:
A.IncreasesB.No changeC.decreases
Follow up1. Air that has reached its water-vapor
capacity is said to be:a. Dry b. unstable c. stable d. saturated2. The ratio of air’s water content to
its capacity to hold water at the same temperature is:
a. Vapor pressure b. relative humidity c. specific humidity d. wet adiabatic rate3. Water vapor makes up what fraction
(%) of atmospheric gases?
ObjectivesI will be able to:
◦Describe how air is lifted to form clouds.
◦Differentiate between the different types of clouds by making a poster.
◦Describe the weather associated with the different types of clouds.
Key Points - CloudsWhen air is compressed the air
temperature rises and the air molecules move faster.
Processes that lift air include orographic lifting, frontal wedging and convergence.
Examples of condensation nuclei include dust, smoke and salt particles.
Nimbus means “rainy cloud”.Cumulonimbus clouds are often
associated with thunder and lightning.
Cloud Formation
• When air is allowed to expand, it cools, and when it is compressed, it warms.
When air is compressed the air temperature rises and the air molecules move faster.
Air compression causes temperature changes even though heat isn’t added or subtracted.
Cloud Formation
Clouds form because as you go up in elevation, it gets colder.
Cold air cannot hold as much water vapor so it transforms into clouds.
Cool, expanded air
Warm, compressed air
Cloud Formation
Four mechanisms that can cause air to rise are orographic lifting, frontal wedging, convergence, and localized convective lifting.
Fill out each box with the underlined words and a picture as we discuss them.
• Orographic lifting occurs when mountains act as barriers to the flow of air, forcing the air to ascend.
1. Orographic Lifting
Cloud Formation
• A front is the boundary between two adjoining of air masses having contrasting characteristics.
2. Frontal Wedging
Processes that lift the air
How does the relatively flat central region of the US receive precipitation?
Orographic Lifting and Frontal Wedging
1. Orographic Lifting 2. Frontal Wedging
Cloud Formation
• Convergence is when air flows together and rises.
3. Convergence
• Localized convective lifting occurs where unequal surface heating causes pockets of air to rise because of their buoyancy.
4. Localized Convective Lifting
Processes That Lift Air
Convergence and Localized Convective Lifting
3. Convergence 4. Localized Convective Lifting
Cloud Formation
For any form of condensation to occur, the air must be saturated.
• Generally, there must be a surface for water vapor to condense on.
Types of Surfaces
• Condensation nuclei are tiny bits of particulate matter that serve as surfaces on which water vapor condenses when condensation occurs in the air.
• Examples of condensation nuclei include dust, smoke and salt particles.
Condensation – How clouds form
Cloud Types and Precipitation
Clouds are classified on the basis of their form and height.
Types of Clouds
Cloud Types and Precipitation
There are three basic forms of clouds. All other clouds one of these three or are combinations or modifications of them.
1. Cirrus (cirrus = “curl of hair”) are clouds that are high, white, and thin.
2. Cumulus (cumulus = “a pile”) are clouds that consist of rounded individual cloud masses.
3. Stratus (stratus = “a layer”) are clouds best described as sheets or layers that cover much or all of the sky.
Types of Clouds by Form
Cloud Types and Precipitation
What type of cloud is this?
Cirrus
Cloud Types and Precipitation
What type of cloud is this?
Cumulus
Cloud Types and Precipitation
What type of cloud is this?
Stratus
Cloud Types and Precipitation
1. High Clouds• Cirrus clouds are high, white, and thin.• Cirrostratus clouds are flat layers of clouds.• Cirrocumulus clouds consist of fluffy masses.
2. Middle Clouds – “Alto”
• Altostratus clouds create a uniform white to gray sheet covering the sky with the sun or moon visible as a bright spot.
• Altocumulus clouds are composed of rounded masses that differ from cirrocumulus clouds in that altocumulus clouds are larger and denser.
Types of Clouds by Height
Cloud Types and Precipitation
3. Low Clouds• Stratus clouds are best described as sheets or
layers that cover most of the sky.
• Nimbostratus clouds are the main precipitation makers.
• Stratocumulus clouds have a scalloped bottom that appears as long parallel rolls or broken rounded patches.
Types of Clouds by Height
Cloud Classification
Answer the following1. What happens when air is
compressed?a. Air temperature rises.b. Air temperature cools.c. Air molecules move faster.d. both a and c2. What term means “rainy cloud”?a. stratus b. nimbus c. cumulus d. cirrus3. Name one example of
condensation nuclei:
