The AtmosphereThe Atmosphere

What is the atmosphere?What is the atmosphere? The thin layer of The thin layer of gasesgases that that

surrounds our surrounds our planet.planet. WeatherWeather is the condition of is the condition of

the atmosphere at a certain the atmosphere at a certain place and time.place and time.

Our atmosphere makes Our atmosphere makes lifelife possible on our planet.possible on our planet.

Provides us with Provides us with oxygen.oxygen. Keeps surface Keeps surface warmwarm so water so water

can exist as a liquid.can exist as a liquid. Protects the surface from Protects the surface from

dangerous dangerous radiationradiation from the from the sun.sun.

Protects us from most Protects us from most meteoroidsmeteoroids or rocks from or rocks from space.space.

WeatherWeather : state of : state of atmosphere at any given atmosphere at any given time and placetime and place– temperaturetemperature–precipitationprecipitation–air pressureair pressure–wind wind –humidityhumidity

ClimateClimate Aggregate (average) of weather Aggregate (average) of weather

conditions over a long period of time.conditions over a long period of time.– ExampleExample: A place that doesn't get much : A place that doesn't get much

rain over many years would have a dry rain over many years would have a dry climate. A place where it stays cold for climate. A place where it stays cold for most of the year would have a cold climate. most of the year would have a cold climate.

Look out your window any day, any Look out your window any day, any time and you see weather. Look out time and you see weather. Look out your window every day for a month or your window every day for a month or longer, observe the weather each day, longer, observe the weather each day, and you can determine the climate. and you can determine the climate.

The Composition of the Atmosphere

NitrogenNitrogen makes up 78% of our atmosphere makes up 78% of our atmosphere OxygenOxygen makes up 21% makes up 21% ArgonArgon makes up almost 1% makes up almost 1% All other gases have only trace amountsAll other gases have only trace amounts

Trace elements/compoundsTrace elements/compounds Carbon dioxideCarbon dioxide: plants use to produce : plants use to produce

food. Plants take in food. Plants take in COCO22 and give off and give off oxygenoxygen as a waste product. as a waste product.

Animals take in Animals take in oxygenoxygen to make energy to make energy and give off and give off COCO22 as a waste product. as a waste product.

Fossil fuelsFossil fuels (coal, oil, natural gas) give (coal, oil, natural gas) give off COoff CO22 when they are burned. Rising when they are burned. Rising COCO22 levels may cause levels may cause global warmingglobal warming..

The fizz in The fizz in sodasoda is really CO is really CO22 bubbles.bubbles. Dry iceDry ice is CO is CO22 in the solid state. in the solid state.

OzoneOzone OzoneOzone is a molecule of is a molecule of

oxygen with oxygen with 33 oxygen atoms oxygen atoms instead of 2.instead of 2.

Often formed when Often formed when lightninglightning interacts with interacts with oxygen in the air or by UV oxygen in the air or by UV rays in the upper rays in the upper atmosphere.atmosphere.

Forms a layer in the Forms a layer in the atmosphere that absorbs atmosphere that absorbs ultraviolet radiationultraviolet radiation from from the sun. Without this layer the sun. Without this layer life might not be possible on life might not be possible on the surface of the planet.the surface of the planet.

Earth’s Early AtmosphereEarth’s Early Atmosphere The Precambrian atmosphere was The Precambrian atmosphere was

composed mainly of composed mainly of nitrogennitrogen and and carbon carbon dioxidedioxide, along with some methane and , along with some methane and ammonia.ammonia.

Volcanoes Volcanoes spewed water vapor, carbon spewed water vapor, carbon monoxide, and even more nitrogen and monoxide, and even more nitrogen and carbon dioxide into the air. Comets also carbon dioxide into the air. Comets also contributed water vapor, but no free contributed water vapor, but no free oxygen.oxygen.

So where did the abundant oxygen that So where did the abundant oxygen that has made life as we know it come from?has made life as we know it come from?

Precambrian LifePrecambrian Life The first life on Earth was The first life on Earth was

cyanobacteriacyanobacteria (like single (like single celled blue-green algae).celled blue-green algae).

They used They used photosynthesisphotosynthesis to to turn COturn CO22 into the food and into the food and energy they needed to energy they needed to survive.survive.

Photosynthesis gives off Photosynthesis gives off oxygenoxygen as a waste product. as a waste product.

So over the millions of So over the millions of years, oxygen given off by years, oxygen given off by algae built up in the algae built up in the atmosphere, while the atmosphere, while the amount of COamount of CO22 declined. declined.

Layers of the Layers of the AtmosphereAtmosphere

PressurePressure PressurePressure is a force that acts is a force that acts

over a certain area.over a certain area. Liquids and gases are Liquids and gases are fluidfluid. Fluid; . Fluid;

are any material that is able to are any material that is able to flowflow. Fluids exert pressure . Fluids exert pressure because of the motion of their because of the motion of their particles.particles.

Pressure will always move from a Pressure will always move from a highhigh pressure to a pressure to a lowlow pressure pressure area. The pressure will always area. The pressure will always try to equalize. You see this try to equalize. You see this when you get a hole in your when you get a hole in your bicycle tire.bicycle tire.

Air PressureAir Pressure

Air Air pressure is the pressure is the result of the column result of the column of air that is of air that is aboveabove you.you.

There is so much air There is so much air above you that at sea above you that at sea level you have 14.7 level you have 14.7 lbs/inlbs/in22 pushing on you. pushing on you.

GravityGravity causes most causes most of the air to be pulled of the air to be pulled down to the surface.down to the surface.

Why are we not crushed Why are we not crushed by air pressure?by air pressure? Air pressure is Air pressure is

equalequal in all in all directions.directions.

So air pushes So air pushes equally in all sides equally in all sides of us. The forces of us. The forces are are balancedbalanced!!

Units of Air PressureUnits of Air Pressure

TV weather stations TV weather stations and aviation use and aviation use inches of mercury.inches of mercury.

Meteorologists (and Meteorologists (and the NWS) use the NWS) use millibars, an SI unit.millibars, an SI unit.

Altitude and DensityAltitude and Density As the air pressure As the air pressure

decreasesdecreases, the density of , the density of the air the air decreasesdecreases. The . The air particles are not air particles are not squashed together as squashed together as tightly the higher one tightly the higher one goes. This is caused by goes. This is caused by gravity!gravity!

The air at sea level and The air at sea level and at 6km has the same 21% at 6km has the same 21% oxygen, but at 6km there oxygen, but at 6km there are are fewerfewer molecules, so molecules, so you take in less oxygen you take in less oxygen with each breath.with each breath.

Temperature and the Temperature and the TroposphereTroposphere Troposphere: Troposphere:

temperature at surface temperature at surface is warmed by the earth is warmed by the earth absorbing energy from absorbing energy from the sunthe sun ..

ConvectionConvection currents currents carry the heat upward, carry the heat upward, so the air so the air coolscools as it as it rises.rises.

The air The air coolscools by about by about 6.56.5°C for every 1-km °C for every 1-km above the ground.above the ground.

Temperature and the Temperature and the StratosphereStratosphere

OzoneOzone absorbs absorbs ultraviolet radiation ultraviolet radiation from the sun, causing from the sun, causing the temperature to the temperature to increaseincrease..

Temperature and the Temperature and the MesosphereMesosphere

This layer does This layer does not not absorb energy absorb energy from the sun, so it from the sun, so it starts to starts to coolcool again.again.

Without Without greenhouse greenhouse gasesgases, , energy pretty energy pretty much passes much passes straight through!straight through!

Temperature and the Temperature and the ThermosphereThermosphere

Solar radiation first hits Solar radiation first hits this layer, so the few this layer, so the few particles that are here can particles that are here can gain lots of energy. They gain lots of energy. They move rapidly, so they have a move rapidly, so they have a very very highhigh temperature. temperature.

But the air is so But the air is so thinthin here here that it takes special that it takes special instruments to measure the instruments to measure the temperature accurately.temperature accurately.

So even though it is very So even though it is very hothot (over 1000°C), it would (over 1000°C), it would feel feel coldcold because there are because there are so few particles to transfer so few particles to transfer heat to you.heat to you.

The TroposphereThe Troposphere LowestLowest (inner) layer (inner) layer weatherweather occurs here occurs here we live in it.we live in it. ““tropotropo” means turning ” means turning

or changing conditionsor changing conditions depth varies from 9km depth varies from 9km

above the poles to 16km above the poles to 16km at the equatorat the equator

thinnestthinnest layer, but layer, but contains most of the contains most of the mass (90%).mass (90%).

The StratosphereThe Stratosphere

““stratostrato ” means layer ” means layer or spreading outor spreading out

Contains the Contains the ozoneozone layer which absorbs layer which absorbs energy and causes the energy and causes the temperature to risetemperature to rise

The ozone layer The ozone layer protectsprotects the surface the surface from dangerous from dangerous UV UV raysrays

The MesosphereThe Mesosphere

DropDrop in in temperature temperature marks beginning of marks beginning of mesospheremesosphere

““MesoMeso” means ” means middlemiddle

Most Most meteorsmeteors burn up hereburn up here

The ThermosphereThe Thermosphere Very Very toptop layer layer Air is very, very Air is very, very thinthin, about , about

1/10001/1000thth as dense as the air at as dense as the air at sea levelsea level

““ThermoThermo” means heat” means heat Extends from Extends from 80km80km to space to space No definite outer edgeNo definite outer edge Very Very hothot (over 1000 (over 1000°C), but °C), but

since air is so since air is so thinthin it would not it would not feel warm at all.feel warm at all.

Divided into two parts, the Divided into two parts, the ionosphereionosphere and the and the exosphereexosphere

The IonosphereThe Ionosphere Energy from sun strips the Energy from sun strips the

electrons from the gas electrons from the gas molecules creating charged molecules creating charged particles called particles called ionsions..

Radio wavesRadio waves can bounce off of can bounce off of ions, allowing radio waves to ions, allowing radio waves to travel great distances.travel great distances.

The The auroraaurora borealis (Northern borealis (Northern Lights) occur hereLights) occur here

The ExosphereThe Exosphere ““ExoExo” means outer” means outer Extends for 1000’s Extends for 1000’s

of milesof miles SatellitesSatellites orbit orbit

herehere No definite No definite edgeedge Molecules Molecules

gradually escape gradually escape out into out into spacespace