The Dynamic Earth: The Atmosphere and Climate

Chapter 3, section 2 Earth’s Atmosphere Relatively thin layer of gases that envelope the earth

Composition of the atmosphere Atmosphere – 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? exosphere thermosphere mesosphere stratosphere troposphere Layers differ in temperature, density and composition 4

Layers of the atmosphere exosphere thermosphere mesosphere stratosphere troposphere What layers of the atmosphere do you think we will focus on in Environmental Science? Why?

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 go Stratosphere Contains 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 ? ? ? ? ? 8

Review: locate the ozone layer and explain its importance exosphere thermosphere mesosphere stratosphere troposphere 9

Thought question: Locate the “planetary boundary layer” in this diagram. What does that mean? exosphere thermosphere mesosphere stratosphere troposphere 10

The sun’s energy reaches the earth as radiation Notice what happens to the incoming solar radiation: Teacher notes: point out the different amounts being reflected and absorbed

*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 effect Only 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 climate 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 climate 2. 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 circulation Air near Earth’s surface is warmer and moister than air at higher latitudes Convective 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 climate Convective circulation along with the earth’s rotation establishes certain patterns within earth’s atmosphere Wind – movement of air within the atmosphere Prevailing winds – blow predominantly in one direction throughout the year Trade winds – belts of prevailing winds that are found in both hemispheres between 30° north and south latitudes Westerlies – prevailing winds blowing from the west between 30° and 60° north and south latitudes Polar 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. surface 2. 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 climate 5. Altitude – increasing altitude results in decreasing temperature (drops 3°F for every 1000’ increase in elevation)

Factors that affect climate 6. Topography of the land Winds carrying moisture from the ocean rise up the windward side of the mountain As air cools, moisture condenses and precipitation falls on the windward side of the mountain Dry 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 Gobi Desert – rain shadow of Himalayas Mohave Desert, U.S. – rain shadow of Sierra Nevada Mountains

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.