The Dynamic Earth:The Atmosphere and Climate

Chapter 3, section 2Earth’s Atmosphere

Relatively thin layer of gases that envelope the earth

Composition of the atmosphereAtmosphere – mixture of gases that surround the Earth; these gases include:

◦Nitrogen – 78%◦Oxygen – 21%◦Other gases, including carbon dioxide, water,

methane – 1%

Layers of the atmosphere – look at the scales on x and y axis carefully; what do you notice?

Layers differ in temperature, density and composition

exosphere

thermosphere

mesosphere

troposphere

stratosphere

Layers of the atmosphere

What layers of the atmosphere do you think we will focus on in Environmental Science? Why?

exosphere

thermosphere

mesosphere

troposphere

stratosphere

Two layers most important to ES are troposphere and stratosphere

Why?Troposphere Life can exist here (part of the biosphere)It provides the gases required for life (oxygen,

carbon dioxide, nitrogen)Where weather occurs (it is part of the water cycle

which is necessary to sustain life on earth)Where most of our air pollutants goStratosphereContains the ozone layer which protects earth from

some of the sun’s UV rays (see next slide…)Some air pollutants reach the stratosphere

The ozone layer is • made of ozone molecules or O3• is located within the stratosphere • filters certain types of damaging ultraviolet

light - UV light can damage the genetic material (DNA) in living things (that is why we wear sunscreen and sunglasses)

Review: name the layers of the atmosphere

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Review: locate the ozone layer and explain its importance

exosphere

thermosphere

mesosphere

troposphere

stratosphere

Thought question: Locate the “planetary boundary layer” in this diagram. What does that mean?

exosphere

thermosphere

mesosphere

troposphere

stratosphere

The sun’s energy reaches the earth as radiationNotice what happens to the incoming solar radiation:

*The 19% that is absorbed by atmosphere and clouds causes the earth to be warmed*This warming effect is called the Greenhouse Effect and is defined as the process by which gases in the atmosphere trap heat near Earth*It is an important function of the atmosphere – it makes earth warm enough to support life

Greenhouse effectOnly certain gases in the atmosphere absorb heat and are called greenhouse gases

Greenhouse gases include:water (H2O)carbon dioxide (CO2)methane (CH4)

Non-greenhouse gases include oxygen and nitrogen

The atmosphere also protects us from objects reaching earth from space The objects usually burn up before reaching earth due to friction as they pass through the atmosphere

And the atmosphere is part of the cycling of water, carbon, and nitrogen which are necessary for life – more on this later….

Summary and review:The earth’s atmosphere carries out many beneficial functions for us:• filters ______________ and keeps some of it from

reaching us• ______________ effect warms the planet• provides a protective barrier for objects from

__________• plays a role in the cycling of _________ and

nutrients

Summary and review:The earth’s atmosphere carries out many beneficial functions for us:• filters UV radiation and keeps some of it from

reaching us• greenhouse effect warms the planet• provides a protective barrier for objects from

space• plays a role in the cycling of water and

nutrients

The atmosphere drives weather and climate

(Chapter 13-1)

Weather = specifies atmospheric conditions over short time periods and within a small geographic areas

Climate = describes patterns of atmospheric conditions across large geographic regions over long periods of time

Mark Twain said “Climate is what we expect;

weather is what we get”

Factors that affect climate1. Latitude – distance from the equator At the equator, sun’s rays are more direct – result is higher

and consistent temperatures, more precipitation (tropical rainforests)

At higher latitudes – sun’s rays are at an angle, less intense, also seasons occur, so climate is cooler and less consistent year-round

The reason for this is the fact that the earth is a sphere

Oblique rays

Vertical rays

Factors that affect climate2. Seasons occur because the Earth is tilted on its axis and revolves around the sun

◦ Each hemisphere tilts toward the sun for half the year◦ Results in a change of seasons◦ Equatorial regions are unaffected by this tilt, so days average

12 hours through the year

Factors that affect climate

3. Atmospheric circulationAir near Earth’s surface is warmer and moister than air at higher latitudesConvective circulation = less dense, warmer air rises and creates vertical currents

◦ Warm air is less dense, it expands, rises and cools

◦ As it cools, water condenses out as precipitation

◦ Cool air sinks replacing warm air

◦ Influences both weather and climate

Factors that affect climateConvective circulation along with the earth’s rotation establishes certain patterns within earth’s atmosphereWind – movement of air within the atmospherePrevailing winds – blow predominantly in one direction throughout the yearTrade winds – belts of prevailing winds that are found in both hemispheres between 30° north and south latitudesWesterlies – prevailing winds blowing from the west between 30° and 60° north and south latitudesPolar easterlies – prevailing winds blowing from the east in the polar regions

Factors that affect climate

4. Oceanic circulation patterns

Two types of ocean currents:1. surface2. deep – very slow moving

These currents result in a redistribution of heat on the planet – from the equator to the poles

Also affects location of nutrients and oxygen

(more on this when we study the hydrosphere)

Notice that the warm (red) currents move away from the equator and the cool (blue) currents move toward the equator and around the south pole

Factors that affect climate5. Altitude – increasing altitude results in decreasing

temperature (drops 3°F for every 1000’ increase in elevation)

Factors that affect climate 6. Topography of the landWinds carrying moisture from the ocean rise up the windward side of

the mountainAs air cools, moisture condenses and precipitation falls on the

windward side of the mountainDry air flows down leeward side of the mountain, often there are

deserts on that side of the mountain – called the rain shadow

Examples of deserts formed by rain shadows

Mohave Desert, U.S. – rain shadow of Sierra Nevada Mountains

Gobi Desert – rain shadow of Himalayas

Factors that affect climate

7. Volcanic activity – emits gases and particles that block sunlight

1816 – called the “Year without a Summer” – due to combination of low solar activity and powerful volcanic eruptions (Tamboro)

Pinatubo 1991

Quick check of understanding:

What factors affect earth’s climate? How many can you list and explain?

Take 2 minutes to review with a partner.