EARTH’S ATMOSPHERE

Origins of the Atmosphere

• Boom.• Our atmosphere was created by gases that

vented from erupting volcanoes.• Outgassing• There were three main gasses emitted:1.Water Vapor2.Carbon dioxide3.Nitrogen

• Now the atmosphere is mainly….• If your not sure look at your…..• ESRT1. Nitrogen2. Oxygen• How did this occur?• Plant life began to grow so they converted

carbon dioxide to oxygen• Photosynthesis

The Structure of the Atmopshere• The atmosphere is broken into four layers:1. Troposphere2. Stratosphere3. Mesosphere4. Thermosphere• The layers in between the spheres are called:• -pauses

Changes in Air Temperature

• There are two cycles that control our weather:1.The daily weather cycle

2.The season weather cycle

Daily Weather Cycle

• Morning-----------

• 2pm----------------

• 6pm----------------

Seasonal CycleMARCH 21-23 DECEMBER 21-23JUNE 21-23 SEPTEMBER 21-23

What Causes Air Pressure?

• Air Pressure: is the weight of the atmosphere• Proof: Weigh a flat basketball compared to a

basketball filled with air. • At sea-level, the air pressure is nearly 15 lbs

per square inch, or 1013.2 mb.• Millibars: the metric unit of atmospheric

pressure.

STRAW PROOF AIR GOES OUT OF THE STRAW SO PRESSURE DECREASES

Less pressure means that the liquid has nothing holding it back so it moves up the straw

Measuring Air Pressure• ometer:• Instrument that measures air pressure.• Use to use mercury as a liquid in it to gauge the air

pressure (like a thermometer) so that is how we got the unit inches of mercury.

• In. of Hg• We also use millibars to measure air pressure

Bar

Factors that Affect Atmospheric Pressure

• Altitude• As air rises it expands and there is less gravity

pushing down on it. • More elevation = less air pressure• Indirect relationship

Altitude (elevation)

Air Pressure

Factors (cont)• Temperature:• If air is cooled it comes together and becomes

more dense• More dense air makes it heavier so there is

more air pressure• If air is heated it’s molecules expand and it

becomes less dense• Less dense air makes it lighter so there is less air

pressureAir Pressure

Temperature

Factors (cont)• Humidity• Is the amount of water vapor in the air• Humid air is less dense than dry air• The mass of water is less than the mass of

nitrogen • The atmosphere is made up of primarily which

gas….• Nitrogen• More humidity = less air pressure Air Pressure

Humidity

Dew Point

• When the humidity of the air cools to a certain point, you see water in some form.

• This temperature in which we see water is what we call the dew point.

• The dew point comes mostly when the greatest change in temperature occurs which is…..

• (Think the daily weather cycle)• The morning

How to Find the Dew Point• Using a sling psychrometer you:1.Record the dry bulb reading2.Record the difference between the dry bulb and the

wet bulb (wet bulb will always be less)3.Go to your ESRT and match up those two numbers

to find the Dew Point

Dry Bulb:

22°C

Wet

Bulb:20°CDiff: 2°C

Relative Humidity

• The percentage of humidity in the air is called the relative humidity.

• We use a sling psychrometer to find this as well.

• You also use the same procedure to find the relative humidity.