The AtmosphereEarth’s Atmosphere and Distribution of Earth’s

Heat on Land and Water

EQ: How do air pressure and temperature vary in the

atmosphere?

StandardsS6E3b; S6E4a,b; S6E5j; S6E6a

The Air Around YouAtmosphereChapter 12Section One

The Air Around YouWeather is the condition of Earth’s

atmosphere at a particular time.Atmosphere: the layer of gases that surrounds

EarthEarth’s atmosphere is composed of nitrogen,

oxygen, carbon dioxide, water vapor, and other gases.

Earth’s atmosphere contains oxygen and other gases that living things need to survive.

Composition of the AtmosphereNitrogen

Makes up ¾ of the air we breathe.Oxygen

2nd most abundant gas in the atmospherePlant and animals take oxygen from their

surroundings and use it to release energy from food in a cellular process.

Is needed for fire to burnOzone

Form of oxygen that has three oxygen atoms in each molecule

Composition of the AtmosphereCarbon dioxide

Is present in small amounts in the atmosphereEssential to lifeAnimals produce carbon dioxideBurning fossil fuels increases the amount of

carbon dioxide in the atmosphere.Water Vapor

Water in the form of a gasProduces clouds

Importance of the AtmosphereEarth’s atmosphere makes conditions on

Earth suitable for living things.Traps energy from the sun which keeps most

of the Earth’s surface warm.Water exist in liquid form.

Air PressureChapter 12Section Two

Air PressureProperties of air:

Consists of atoms and molecules that have mass

MassDensityPressure

Pressure is the force pushing on an area or surface.

Air pressure is the result of the weight of a column of air pushing down on an area.

Air PressureHow are mass and air pressure related?

The weight of air in the atmosphere causes air pressure.

So why doesn’t air pressure crush objects?The reason is that the molecules of air push in

all directions. The air pushing down on an object is balanced by the air pushing up on the object.

How does the density of air affect air pressure?Denser air exerts more pressure than less

dense air.

Measuring Air PressureAn instrument used to measure air pressure is

a barometer. Two kinds of barometers

Aneroid Mercury

Unit of Air Pressure2 different units of measurement

Inches of mercury millibars

How does altitude affect air pressure?Altitude, or elevation,

is the distance above seal level.

Air pressure decreases as altitude increases.Less oxygen

molecules to breathe at higher altitudes.

As air pressure decreases, so does density.

Altitude Affects Air PressureSea level air has the weight of the whole

atmosphere pressing on it.So air pressure is greater at sea level.The air near the top of the atmosphere has

less weight pressing on it , and thus has lower air pressure.

Altitude Also Affects DensityAs you go through the atmosphere, the

density of the air decreases.This means the gas molecules that make up

the atmosphere are farther apart at high altitudes than they are at sea level.

The air contains 21% oxygen.There are fewer oxygen molecules at high

altitudes.

Layers of the AtmosphereKey Concepts

What are the four main layers of the atmosphere?

What are the characteristics of each layer?

What are the layers of the atmosphere?Scientists divide Earth’s atmosphere into four

main layers classified according to changes in temperature. TroposphereStratosphere (Ozone layer)MesosphereThermosphere

Ionosphere Exosphere

TroposphereWe live in the

troposphere.All weather and

water vapor are in this layer.

Gets colder as you go up.

Clouds0-18 km

Stratosphere2nd layer of the atmosphereTemperature s get warmer are you go up.12 – 50 kmContains the Ozone layer.

Absorbs ultraviolet radiation

MesosphereProtects Earth’s surface from being hit by

meteoroids.Coldest region of atmosphere50 – 80 km

ThermosphereOutermost layer of Earth’s atmosphereAbove 80 kmAir is thin, it is very hot because the sun

strikes this layer firstDivided into 2 layers:

Ionosphere, lower layer of thermosphere 80 – 400 km Radio waves bounce back to Earth’s surface

Exosphere, outer layer of thermosphere 400 – 1000 km Artificial satellites orbit here

Energy from the SunKinds of energy from the sun

Visible lightInfrared radiationUltraviolet radiation

Can cause sunburns, skin cancer, and eye damageWhen Earth’s surface is heated, it radiates most

of the energy back into the atmosphere as infrared radiation.

Greenhouse effect Process by which a blanket of gases around the

Earth that hold heat in the atmosphere.

Heat TransferThree forms of heat transfer:

Radiation Direct transfer of energy by electromagnetic waves

Ex. – heat from the sun travels by radiation Conduction

Direct transfer of heat from one substance to another substance by direct contact. Ex. – pot on a stove

Convection The transfer of heat by the movement of fluid

Ex. – Upward movement of warm air and the downward movement of cool air form convection currents.

Heat Transfer

WindsA wind is the horizontal movement of air from an

area of high pressure to an area of low pressure.Winds are

Caused by the unequal heating of the earth.Cool, dense air flows under warm, less dense air.

Measuring windSpeed (anemometer)Direction (wind vane)

Wind-chill factor – the increased cooling a wind can cause.

Local WindsWinds that blow over short distances.Caused by the unequal heating of Earth’s

surface within a small area.During the day, land warms up faster than

water.At night, the land cools faster than water.

Local WindsSea Breeze

Local wind that blows from an ocean or lake.

Local WindsLand Breeze

The flow of air from land to a body of water.

Global WindsWinds that blow steadily from specific

directions over long distancesCreated by unequal heating of Earth’s

surface.Occur over a large areaGlobal convection currents

Produced by temperature differences between the equator and the poles

Coriolis EffectEarth’s rotation makes winds curve

Global Wind BeltsMajor wind belts

Trade windsPolar easterliesPrevailing westerlies

Atmosphere ReviewCan you answer the following questions:

What are the main gases in the atmosphere?Name the 6 layers of the atmosphere?What are 3 forms of heat transfer?What causes wind?What are the major global winds?