Download Properties of the Atmosphere Lesson 2

Properties of The Atmosphere
UNIT 9
STANDARDS: NCES 2.5.1, 2.5.2
LESSON 2
Lesson Objectives
 In this lesson, you will learn about:
 The
various properties of the atmosphere
 How the different properties interact
 Why do atmospheric properties change
with altitude
 How clouds form
 The basic characteristics of cloud types
Temperature versus Heat
 Temperature is a
measurement of the
amount of heat
generated by moving
molecules.
 Measuring temperature
uses the Kelvin scale.
 The Kelvin scale is set
to absolute zero, the
point where all motion
stops.
 Heat is the transfer
of energy from hot
to cold.
Dew Point
 Definition
 Saturation
 Condensation
 The temperature which air
must be cooled to reach
saturation.
 When the air hold as much
water as possible
 A state change from a gas to a
liquid. Generally forms in
dew,fog, or rain.
Relative Humidity
 Humidity
 The amount of water in
the air.
 The ratio of how much
 Relative Humidity
water is in the air
versus how much water
the air can hold. Like
how “full” the air is.
 Expressed in a
percentage.
Wind
 As the air heats, it
 As the warm air
expands.
rises, cool air
settles.
 As the volume of air
expands, the density  The upward
decreases.
movement creates a
convection current.
 Less dense (warm)
air will rise.
 This movement is
called “wind”.
Wind
 We call the movement of the air in the atmosphere. Some
parts of the atmosphere are warmer than other parts. Since
warm air is lighter than cool air, it rises. Cool air sinks
beneath the warm air. When the air moves that way, we feel
the wind blow.
Warm air rises and moves up
Cool air settles and move in
Section Review 9.2.1
 How is dew point related to saturation?
 How does atmospheric pressure
change with altitude?
 Compare and contrast humidity and
relative humidity.
 Explain how winds form.
Clouds: Introduction
 The temperature differences in the
atmosphere also cause clouds to form.
 Clouds are made up of water vapor, so they
provide rainwater.
 Rainwater lets plants, animals, and people
live.
 Sometimes the temperature is so cold that
the clouds are made of ice crystals, rather
than water, and then snow and ice fall instead
of rain.
How clouds form
 Two conditions have to be met before clouds
can form. The air has cool enough so that the
water in the air can condense. When the air
rises, it cools off. That means that the water
vapor rising will turn back into water.
 The second condition for clouds to form
requires some solid surface be present for
water to “stick to”. That is why dust in the
atmosphere is so important.
Formation of “droplets”
 Most clouds are formed high above the
earth’s surface when rising air cools off and
the water vapor condenses by sticking to
solid particles in the air.
 These tiny bits of water clinging to dust
particles are called water droplets. They are
so tiny, that they float and keep rising on air
currents as warm air rises.
 More and more droplets are formed, and they
get larger as more water vapor condenses
and sticks to them.
Let it Precipitate
 Each water droplet reflects light. Direct sunlight looks
white when it is reflected, and that is why a cloud
looks white on the side facing the sun.
 On the other side of the cloud, the side not facing the
sun, the cloud looks gray.
 Since water and ice are heavier than gas, water
droplets eventually get too heavy to stay in the air.
 Then depending upon how warm or cold the air
temperature is, rain, sleet, snow, or hail falls to the
earth.
Types of Clouds (Binary name)
 Cirro: Clouds above
 Cirrus: Wispy or
6000 meters
 Alto: Middle clouds
between 2000 and
6000 meters
 Strato: Clouds from
ground level to 2000
meters.
feather clouds
 Cumulus: fluffy
clouds
 Stratus: layered
clouds
 Nimbus: Rain
Clouds
The name of a cloud is formed by joining the two parts.
Stratocumulus: Low level, fluffy cloud
Cloud Chart
Cloud Chart with Descriptions
Section Review 9.2.2
 Explain why a cumulonimbus cloud is
not considered to be a low, middle, or
high level cloud.
 Describe the process that causes a
water droplet to fall to the Earth.
 What determines whether precipitation
will fall as rain or snow?