Chapter 7

Weather and Climate

*

*Describe what weather is, what

affects it, and where it occurs.

*Explain the connection between

air pressure and wind.

*

*Many factors affect a

region’s weather.

*

*atmosphere - The layer of gases

that surround Earth.

*troposphere - The layer of the

atmosphere closest to the surface

*insolation - The amount of the Sun’s

energy that reaches earth at a

given time or place.

*air pressure - The force exerted on a

given area by the weight of the air

above it.

*convection cell - A circular pattern of

rising air, sinking air, and winds.

*sea breeze - Wind that blows from sea

to land.

*land breeze - Wind that blows from

land to sea.

*Coriolis effect - The shift in winds to

the right or left caused by Earth’s

rotation.

*

*As you climb a high mountain, the air

gets colder.

*This change in temperature would

occur because you were traveling

upward through the atmosphere, the

layers of gases that surround Earth.

*The atmosphere extends about 700

kilometers high.

*The layer of the atmosphere closest to

Earth’s surface is the troposphere; this

is where most of our weather occurs.

*The troposphere is about 11 kilometers

(7 miles) thick and contains about 80

percent of the total amount of air in

the atmosphere.

*Air is mainly a mixture of gases, dusts,

and water vapor.

*Jet airplanes normally fly within the

stable stratosphere; the stratosphere

contains the ozone layer, which absorbs

the harmful rays from the Sun.

*Rock fragments from space sometimes

burn up in the next layer, the

mesosphere, where the coldest

temperatures are found.

*The outermost layer the thermosphere,

is where space shuttles orbit.

*

Weather is the state of Earth’s

troposphere at a given time and place.

Weather variables which include

temperature, wind, moisture, cloud

cover, and precipitation can change

periodically.

*People have always tried to predict

weather.

*The ancient Egyptians relied mainly

on stars so they would know when

the Nile River would flood.

Scientists can obtain data

by using weather balloons

which get readings while

going through the

atmosphere, weather

satellites which provide

information from space,

and Doppler radar can show

an area’s current weather,

including precipitation,

wind direction, and wind

speed.

*

Fact and Opinion

“Oxygen is the most important gas in

the troposphere, because people need

it to breath.”

Is this a fact or an opinion? Explain.

This statement is an opinion because we

need all of the gases equally.

They all support our and other living

organisms life functions.

Critical Thinking

Why is it important to be able to

predict the weather accurately?

How to dress appropriately,

whether food must be gathered in

advanced,

when to plant or harvest crops,

and to know when to build shelter.

*

*In February it might be hot in

Argentina and cold in Michigan

because as the sunlight reaches the

Earth, the Sun’s energy penetrates the

atmosphere at different angles and

warms Earth’s surface.

*As the surface is warmed it also

warms the air above it.

*The angle of insolation is the angle

at which sunlight hits Earth’s

surface.

*As the angle of insolation increases,

the air becomes warmer.

*The greater the angle, the more

intense the Sun’s rays.

*The rays are the most intense when

the Sun is directly overhead.

*The angle of insolation depends on

several factors: latitude, time of

year, and time of day.

*The angle is greater near the

equator and smaller near the poles.

*The Sun’s rays are less

concentrated and more spread out

near the poles, so they do not warm

the surface there as much.

*Because Earth is on a tilted axis,

seasonal differences affect

insolation.

*In the summers of the Northern

Hemisphere, the Sun’s rays hit Earth

at steeper angles than it does for

the winter.

*Insolation also varies during the course

of the day.

*At dawn, the Sun appears close to the

horizon, and the angle of insolation is

small.

*By midday, the Sun appears much

higher in the sky, and the angle of

insolation is the greatest.

*At dusk, the angle of insolation is

small once again.

*You can measure the angle of

insolation by the shadows it casts.

*The shorter the shadow, the steeper

the angle of insolation.

*

*We use three different scales, the

Fahrenheit scale, the metric Celsius

scale, and the Kelvin scale.

*The Kelvin scale does not have any

negative numbers.

*Water freezes at 320F, 00C, or 273 K.

Water boils at 2120F, 1000C, or 373 K.

*An average room temperature is about

720F, 220C, or 295 K.

*

Fact and Opinion

“Solar energy enters the atmosphere

and warms Earth’s surface and the air

above it.”

Is this a fact or an opinion?

This is a fact, based on evidence.

The Sun’s energy’s warming of Earth is

not an opinion.

Critical Thinking

Why does the angle of insolation

change between midday and

evening, and how does this affect

the air temperature?

The angle of insolation decreases

because of Earth’s rotation, and the air

temperature usually decreases.

*

*Leaves scatter in the wind because the

force of the impact of the air particles is

what pushes the leaves.

*Air particles still move even if it is not a

windy day.

*Air particles have mass so Earth’s gravity

attracts them.

*Standard air pressure or the air pressure

at sea level is about 1 kilogram per square

centimeter.

*A balloon that is filled has expanded

until the air pressure inside the balloon

is higher than the air pressure outside

the balloon.

*When you release the balloon the higher

pressure air can escape, reducing the

pressure inside the balloon.

*When air flows out of the balloon,

moving from an area of high air pressure

to an area with low air pressure it is

called wind.

Earth’s air pressure varies; the higher

you go - the less air pressure. This

happens because there aren’t as many

air particles being pulled toward Earth

by gravity.

Air

pressure

variations

help

produce

wind.

As air warms it spreads out and takes up a

larger area resulting in less air in a given

volume. The air is then less dense and its

pressure decreases. Warmer air with lower

density and pressure rises above cooler air.

*

If a nearby place is warmer and at a

lower pressure, air will move from

the high-pressure area to a low-

pressure area.

This is called surface wind.

Unequal heating and cooling of a

region’s air forms a convection cell.

*

During the day the wind blows from the

water to the land, a sea breeze; at

night the wind usually reverses, going

from the land to the sea, a land breeze.

During the day, air expands over the

land faster than air over water, and the

cold air blows towards land.

*

Weather maps, such as a station model,

are used to display wind speed and

direction.

Anemometer is a device that has cups

on it, it measures wind speed.

A weather vane is a device that

measures the wind’s direction; the

arrow points in the direction the wind

blows.

*Barometer measures the surrounding air

pressure.

*The old

barometers

measured the air

pressure in

millibars, the air’s

ability to maintain

the height of a

column of

mercury.

*

Fact and Opinion

"Land breezes are more refreshing

than sea breezes." Is this statement a

fact or opinion? Explain your answer.

This statement is an opinion. It is based

on one’s preference, not on facts.

Critical Thinking

What role do changing air temperatures

play in a convection cell?

In a convection cell, warm air rises and is

replaced by surrounding cooler air. As the

warm air cools, it sinks, and completes the

cycle.

*

*Winds blow from

areas of higher

pressure to areas of

low pressure.

*However, Earth’s

rotation pushes the

winds to either the

right or the left; this

is called the Coriolis

effect.

*The Coriolis effect causes winds in the

Northern Hemisphere to curve to the

right, or clockwise.

*In the Southern

Hemisphere,

the winds curve

to the left, or

counter-

clockwise.

*

*Global winds are sometimes called

prevailing winds.

*The Coriolis effect causes these winds to

curve.

*Trade winds, the winds that blow toward

the equator, are curved to the west by

the Coriolis effect.

*The winds that blow towards the poles

curve to the east.

*They are called westerlies.

*These

winds are

referred to

by the

direction

from which

they come.

*

Fact and Opinion

“The Coriolis effect causes winds to

curve to the right or the left.” Is this

statement a fact or an opinion?

Explain your answer.

It is a fact, based on verifiable evidence.

Earth’s rotation pushes the winds to

either the right or the left, this shift is

called Coriolis effect.

Critical Thinking

What causes global wind patterns?

Convection currents set air into

constant motion, producing global

winds due to the Earth’s rotation.