Layers of the Layers of the AtmosphereAtmosphere

Weather and ClimateWeather and Climate

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

over a certain area.over a certain area. Liquids and gases are fluids.Liquids and gases are fluids.

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

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

Inflating exampleInflating example Air inside a ball Air inside a ball

pushes against the pushes against the sides. The more sides. The more air we put in a ball, air we put in a ball, the more the the more the molecules push. molecules push. So the pressure So the pressure increases as we increases as we add air.add air.

Remember this Remember this

Air PressureAir Pressure

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

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

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

equal in all equal in all directions.directions.

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

Diagram on page 5Diagram on page 5Analogy for air Analogy for air pressurepressure

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

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

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

Shows Shows density of airdensity of air

Layers in a different diagram

Temperature and the Temperature and the TroposphereTroposphere Troposphere: Troposphere:

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

Air cools as it rises (air Air cools as it rises (air molecules lose molecules lose energy)energy)

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

In 10 KM air will coolIn 10 KM air will cool6.5*10=656.5*10=65

Temperature and the Temperature and the StratosphereStratosphere

Ozone absorbs Ozone absorbs ultraviolet radiation ultraviolet radiation from the sun, from the sun, causing the causing the temperature to temperature to increase.increase.

Temperature and the Temperature and the MesosphereMesosphere

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

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

Temperature and the Temperature and the ThermosphereThermosphere

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

But the air is so thin here But the air is so thin 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 hot (over 1000°C), it would hot (over 1000°C), it would feel cold because there are feel cold because there are so few particles to transfer so few particles to transfer heat to you.heat to you.

The TroposphereThe Troposphere Lowest (inner) layerLowest (inner) layer weather occurs hereweather occurs here we live in it.we live in it. ““tropo” means turning or tropo” means turning or

changing conditionschanging conditions depth varies from 9km depth varies from 9km

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

shallowest (least thick) layer, shallowest (least thick) layer, but contains most of the but contains most of the mass (90%).mass (90%).

The StratosphereThe Stratosphere

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

Contains the ozone Contains the ozone layer which absorbs layer which absorbs energy and causes energy and causes the temperature to the temperature to riserise

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

The MesosphereThe Mesosphere

Drop in Drop in temperature temperature marks beginning marks beginning of mesosphereof mesosphere

““Meso” means Meso” means middlemiddle

Most meteors Most meteors burn up hereburn up here

The ThermosphereThe Thermosphere Very top layerVery top layer Air is very, very thin, about Air is very, very thin, about

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

““Thermo” means heatThermo” means heat Extends from 80km to spaceExtends from 80km to space No definite outer edgeNo definite outer edge Very hot (over 1000Very hot (over 1000°C), but °C), but

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

Divided into two parts, the Divided into two parts, the ionosphere and the ionosphere 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 ions.particles called ions.

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

The aurora borealis The aurora borealis (Northern Lights) occur here(Northern Lights) occur here

The ExosphereThe Exosphere ““Exo” means Exo” means

outerouter Extends for Extends for

1000’s of miles1000’s of miles Satellites orbit Satellites orbit

herehere No definite edgeNo definite edge Molecules Molecules

gradually escape gradually escape out into spaceout into space