Weather and
Climate
Chapter 2
Weather Factors
Section 3 Key Terms
• Wind—
The horizontal movement of air from
an area of high pressure to an area
of lower pressure.
• Anemometer—
An instrument used to measure wind
speed.
• Wind-chill factor—
Increased cooling caused by the wind.
Section 3 Key Terms (con’t)
• Local winds—
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Winds that blow over short distances.
Global winds—
Winds that blow steadily from specific directions
over long distances.
Coriolis Effect—
The way Earth’s rotation makes winds in the
Northern hemisphere curve to the right and
winds in the southern hemisphere curve to the
left.
Jet Streams—
Bands of high-speed winds about 10 kilometers
Objective
The students will explain
what causes winds and
describe major wind
belts and where they are
located.
What Causes Wind?
• Brain Pop- Wind
• Wind is the horizontal movement of
air. The air always moves from an
area of high pressure to an area of
lower pressure.
• Differences in air pressure are
caused by differences in how places
are heated by the sun. Warm air
has less pressure than cooler air.
What Causes Wind?
Measuring Wind
• The name of a wind tells you where the
wind is coming from. For example, a
west wind blows from the west.
• Wind speed is measured with an
anemometer.
• Wind direction is
measured with a wind
vane.
Types of Winds
• Local winds are winds that blow
over a short distance. A cool
breeze blowing from the water
over a beach is an example of a
local wind.
• A global wind is a wind that blows
steadily over long distances. A
global wind blows from the same
directions every time.
Global Wind Belts
• Earth rotates from east to west. Earth’s
rotation makes global winds curve. The
way that winds curve is called the Coriolis
effect. The Coriolis
effect makes winds in
the Northern
hemisphere curve to
the right. It makes
winds in the Southern
hemisphere curve to
the left.
Global Wind Belts
• A series of
wind belts
circles the
earth.
Between
the wind
belts are
calm areas.
Wind Belts
Global Wind Belts
 High-speed
winds called
jet streams
blow at the
top of the
troposphere.
Jet streams
Sections 4 & 5 Key Terms
• Humidity—
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A measure of the amount of water vapor in the air.
Relative humidity—
The percentage of water vapor in the air compared
to the maximum amount the air could hold at that
temperature.
Dew point—
The temperature at which condensation begins.
Psychrometer—
An instrument used to measure relative humidity,
consisting of a wet-bulb thermometer and a drybulb thermometer; also known as a hygrometer.
Rain gauge—
An instrument used to measure the amount of
precipitation, consisting of an open-ended can
topped by a collecting funnel and having a collecting
tube and measuring scale inside.
Objective
The students will describe
how relative humidity is
measured and name the
three main types of clouds.
Water in the Atmosphere
• The water cycle is the movement of
water between the atmosphere and
Earth’s surface. During the water
cycle, water enters the air through
evaporation. Evaporation is when a
liquid becomes a gas.
• Humidity is the measure of how
much water vapor is in the air.
Warm air can hold more water vapor
than cold air.
Water in the Atmosphere
• Relative humidity is a percentage
measurement. Relative humidity is the
percentage of water vapor in the air
compared to how much humidity the air
can hold.
Measuring Humidity
 A psychrometer, or
hygrometer, is an
instrument that
measures relative
humidity. A
psychrometer has two
thermometers. One
thermometer has a wet
cloth covering it. You
can tell the relative
humidity of the air by
comparing the
temperatures on the
two thermometers.
How Clouds Form
 Condensation is when a gas becomes a
liquid. When this happens in the
atmosphere, clouds form. For clouds to
form, there must be cooling in the
atmosphere and particles in the air.
 Cold air holds less water vapor than
warm air. When air cools, water vapor
condenses into little drops of water or
ice crystals. The temperature at which
this happens is called the dew point.
Types of Clouds
 There are three main types of clouds:

cirrus, cumulus, and stratus. Cirrus clouds
are wispy clouds that form high in the sky.
Cumulus clouds look like fluffy piles of
cotton. Cumulus clouds can produce
thunderstorms. Thunderstorm clouds are
called cumulonimbus clouds. Stratus clouds
are flat layers of clouds. Stratus clouds
usually cover most of the sky. Stratus
clouds that produce rain are called
nimbostratus clouds.
Clouds that form near the ground are called
fog. Fog often forms when the ground
cools at night. Fog is common near bodies
Objective
The students will identify
the main types of
precipitation and describe
how they are measured.
Types of
Precipitation
• Precipitation is any form of
water that falls from
clouds and reaches Earth’s
surface. Types of
precipitation include rain,
snow, sleet, hail, and
drizzle. The types of
precipitation are classified
by their size and how they
form and reach the surface
of Earth.
Measuring Precipitation
• Snow can be measured with a measuring
stick. It can also be measured by
melting the snow and measuring how much
water there is.
• Rain is measured
with a rain gauge.
Making Clouds
• To make a cirrus cloud, take one fourth of a
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cotton ball and pull it apart into feather-like
pieces.
To make a stratus cloud, take the rest of
that cotton ball and pull it apart slightly into
a flat piece.
To make a cumulus cloud, take 2 cotton
balls. Pull them apart slightly to make them
puffy.
Now that you’ve made each type of cloud,
sort the characteristics of each type of
cloud and write them next to your cloud
sample.
Making Clouds
Color
Shape/Physical Description
Weather
White
• look like big puffy cotton balls
• flat at the bottom with lumpy tops
• often have a popcorn-like
appearance
• indicate fair weather,
but can get very tall
and turn into a
thunderhead that
brings thunderstorms
White
• long, thin, wispy streamers
• thin appearance is because they are
very high in the sky
• made of ice crystals
• usually means fair
weather, but can be a
sign of approaching
weather systems and
air disturbances
Grey
• form layers with no distinct edges;
look like flat sheets of clouds
• create overcast blankets
• flat and straight
• low clouds that cover the sky
• create overcast skies
and often bring rain
Making Clouds
Cloud
Type
Color
Shape/Physical Description
Weather
Cumulus
White
• look like big puffy cotton balls
• flat at the bottom with lumpy tops
• often have a popcorn-like
appearance
• indicate fair weather,
but can get very tall
and turn into a
thunderhead that
brings thunderstorms
Cirrus
White
• long, thin, wispy streamers
• thin appearance is because they
are very high in the sky
• made of ice crystals
• usually means fair
weather, but can be a
sign of approaching
weather systems and
air disturbances
Stratus
Grey
• form layers with no distinct edges;
look like flat sheets of clouds
• create overcast blankets
• flat and straight
• low clouds that cover the sky
• create overcast skies
and often bring rain
Brain Pop
• As you watch the video,
answer the questions on
the worksheet!
• Humidity