Air Pressure &Layers of the Atmosphere

Air Pressure the force exerted on

you by the weight of tiny particles of air

the particles have weight and take up space.

Why doesn't all that pressure squash me?

You have air inside your body too

The air inside your body is pushing out as the air outside your body is pushing in.

Air Pressure Earth's atmosphere is

pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch) at sea level.

The force on 1,000 square centimeters (a little larger than a square foot) is about a ton!

Air Pressure As your altitude

increases the air pressure decreases.

As your altitude decreases the air pressure increases.

This is an inverse relationship!

Barometers are used to measure air in "inches of mercury“ (in Hg) or in "millibars" (mb).

Air pressure can tell us about what kind of weather to expect as well.

If a high pressure system is on its way, often you can expect cooler temperatures and clear skies.

If a low pressure system is coming,

then look for storms and rain.

Pressure & Weather

Early Earth Atmosphere A dense atmosphere emerged from the vapor and

gases that were given off as the planet began cooling. These gases consisted of: Hydrogen (H2) Water Vapor (H2O) Methane (CH4) Carbon Oxides (CO2, CO)

What’s missing? Oxygen!

Early algae and plants eventually changed the atmosphere by giving off “free” oxygen (O2).

Composition of Air Today Nitrogen (N2) 78.084 % Oxygen (O2) 20.9476 % Argon (Ar) 0.934 % Carbon Dioxide (CO2) and other trace

elements 0.0344 %

Troposphere

90% of content of the atmosphere within 16 km of surface

Most weather occurs here

Temperature goes down with altitude

Stratosphere Contains ozone

layer which plays a major role in regulating temperature

Temperature goes up with altitude

Ozone Layer

Found in the Stratosphere

Ultra-Violet light creates O3 from O2

Prevents a lot of UV radiation from reaching surface

O3 destroyed by manmade gasses (CFCs)

Mesosphere The mesosphere is characterized by

temperatures that quickly decrease as height increases.

With increasing distance from Earth's surface the chemical composition of air becomes strongly dependent on altitude and the atmosphere becomes enriched with lighter gases.

Thermosphere In the thermosphere, temperature

increases with altitude because molecular oxygen absorbs the intense solar radiation.

Auroras are found in this layer

Exosphere/ Ionosphere The outermost layer of the Earth's atmosphere. The exosphere is a transitional zone between

Earth's atmosphere and interplanetary space.

Lab: Air Pressure Eight stations Start at your group station Rotate COUNTERCLOCKWISE Spend 2-3 minutes at each station You have 20 minutes total Questions? Go!