The Earth’s Atmosphere

What is the atmosphere? View of the atmosphere from the space shuttle thin layer of gases surrounding the Earth no well-defined upper boundary – just fewer and fewer atoms density decreases with altitude because number of atoms decrease

Air Pressure atmosphere – exerts pressure Why? Because the atoms have weight. Gravity holds it on the Earth Pressure is higher near surface because more atoms pressing from above. sea level pressure = 15 lb/in2

Think about air pressure as being a stack of books. Here at the surface of the earth, we have more air “stacked” on top of us. That means we feel more pressure than if we were higher in the atmosphere. http://curriculum.calstatela.edu

Fill in this as we go along

Composition of Atmosphere atmosphere is a mixture of gases solid particles water droplets Small changes are always happening

Permanent Gases – they are always in the air! N2: nitrogen 78% O2: oxygen 21% This means that most of what you breath is NOT oxygen! lesser amounts of other gases

Variable Gases – This means the percents are always changing. Water vapor (H20) – can change by the minute! Carbon Dioxide (CO2) Ozone (O3)

Water Vapor This satellite image shows the relative amounts of water vapor: Dark – low water, white – high water vapor source of this gas: evaporation from Earth’s surface water cycle – moves water between oceans, land and atmosphere 75% Earth’s surface covered by some form of water

Carbon Dioxide (CO2) What do you think this graph is telling us about the amount of carbon dioxide in the air year by year? sources: respiration, organic decay, volcanoes, natural and man-made caused fires, burning of fossil fuels. important Greenhouse gas More Carbon dioxide means more heating of the Earth

highest concentration in stratosphere Ozone (O3) consists of 3 O atoms (O2 + O = O3 ) highest concentration in stratosphere shields surface from UV radiation It is good for us up in the stratosphere but bad at the surface where we are. Why? Because it forms smog – a type of air pollution.

Solids in the atmosphere http://learningoasis.org/mrmc Pollen Copyright © Michael Collier Dust particles from combustion small solid particles put in the air by nature or humans examples: volcanic ash, salt in sea spray, pollen from plants, and ash from burning vegetation or fossil fuels

Fill in this chart Root prefix Prefix meaning New Word Fact(s) Sphere Ball, globe (layer of the atmosphere) Tropo- Turn, turning, change Troposphere Strato- Layer Stratosphere Meso- Middle Mesosphere Thermo- Heat Thermosphere Iono- Charged; characterized by ions Ionosphere Exo- Out of; away from; former Exosphere

Structure of the Atmosphere no clearly defined upper limit density decreases with elevation We divide the atmosphere into layers based on: Changes in temperature

Layers from Earth’s surface Troposphere Stratosphere Mesosphere Thermosphere The thermosphere has two parts: ionosphere and exosphere. Let’s learn a little about each layer!

Troposphere lowest layer; temperature decreases with altitude thinnest layer (8-16 km, avg. 11 km) where weather occurs, where we live

Troposphere – when a cloud reaches the top of this layer, they cannot go higher so they flatten out. Picture taken by the space shuttle.

Stratosphere found above the troposphere temperature rises with elevation Ozone Layer located here. Remember what we learned about ozone already? Without the ozone layer protecting us, we could not live on the surface of the Earth!

Mesosphere above the stratosphere temperature decreases with altitude Meteorites and space dust burns up in this layer

Thermosphere above the mesosphere temperature increases with altitude contains two parts – ionosphere and exosphere

Ionosphere contains ions: charged particles Visible light is given off when ions are hit by energy from the sun. This produces auroras. They are often called northern lights and are seen at night. Quartz Lake State Park, Alaska (Curtis, 1996) http://apod.nasa.gov

Exosphere The exosphere is the outer part if the atmosphere. Fewer and fewer atoms are found as you get farther from the surface of the earth. Because of this, there cannot be an actual point where you are no longer in the atmosphere. Satellites orbit in the exosphere.

What do you know about these layers?

Final 5 2 C questions Homework question: Using what we have discussed in class today, write a definition of the Earth’s atmosphere in your own words.