(WC) Earth's Atmosphere Lesson

Earth's Atmosphere

Layers of the Atmosphere Diagram In order to truly understand weather and climate you must have an understanding of the Earth's atmosphere.

The earth's atmosphere is composed of gases of just the right types and in just the right amounts to warm the earth to temperatures suitable for life. The effect of the atmosphere to trap heat is the true "greenhouse effect".

The Earth's atmosphere is divided into 5 layers

  • The troposphere
  • The stratosphere
  • The mesosphere
  • The thermosphere
  • The exosphere

Troposphere 

  • Tropo - means "turning" or "changing" 

  • Extends from the surface of the Earth to 10 km above surface. 

  • Contains approximately 90% of all the Earth's gases (air). 

  • Layer where most weather occurs. 

Stratosphere 

  • Strato - means "layer" or "spread out" 

  • Extends from10 km above surface to 50 km above surface. 

  • Contains the ozone layer. 

Mesosphere 

  • Meso - means "middle" 

  • Extends from 50 km above surface to 80 km above surface. 

  • Coldest layer of the atmosphere. 

  • Meteors are seen as shooting stars. 

Thermosphere 

  • Thermo - means "heat" 

  • Extends from 80 km above surface to 500 km above surface. 

  • Is very hot (can be over 1000º C) but it does not feel hot. 

FYI: the thermosphere does not feel hot you must first understand the difference between temperature and heat. 

  • Temperature is an average measure of how much kinetic energy moving particles have. Particles in the troposphere have a lot of energy and are moving very fast so their temperature is high. 

  • Heat is felt when that energy (the thermal energy) is transferred between colliding objects that are at different temperatures. 

So…even though the particles have a lot of energy, the layer is almost a vacuum so there is not enough contact with the few atoms of gas to transfer much heat to your skin so you wouldn't feel warm. 

Exosphere 

  • Exo - means "outer" 

  • Extends from over 500 km above surface to where it merges with outer space.

The atmosphere is a mixture of gases that surround the earth.

The Earth's Atmosphere is composed of:

  • 78% nitrogen
  • 21% oxygen
  • 1% water vapor, argon, carbon dioxide, neon, helium, and other gases

Atmosphere Gases Pie Chart

As stated in the presentation above, Earth is surrounded by a blanket of air composed of nitrogen, oxygen, and argon, as well as trace amounts of other gases. Our planet's atmosphere, extends hundreds of kilometers from Earth and protects Earth's surface from damaging solar radiation.

Atmosphere and Altitude

A relationship between, altitude, pressure, density, chemical composition and temperature exists.

Air Pressure

Air is all around us and that air exerts pressure in all directions.

At sea level, the air pressure is about 14.7 pounds per square inch. As your altitude increases (for example, if you climb a mountain), the air pressure decreases. At an altitude of 10,000 feet, the air pressure is 10 pound per square inch (and there is less oxygen to breathe). 

Air pressure is measured with a barometer. An aneroid barometer is a scientific instrument used in meteorology to measure atmospheric pressure. A mercury barometer is a device that uses the various physical properties of mercury contained in a tube to measure barometric pressure.

On a weather map an L marks an area of low pressure while an H marks an area of high pressure.

Air Density

Air density decreases with altitude.

Air Temperature

Temperatures in the atmosphere change with altitude. Density and pressure correlate with a decrease as altitude increases.

Air temperature is usually measured with a thermometer.

Temperature is different. The decreased air pressure causes the air to expand and become cooler.

When temperature is graphed with altitude the graph will display a more zigzag like line.

Temperature in the Atmosphere Graph

[CC BY 4.0] UNLESS OTHERWISE NOTED | IMAGES: LICENSED AND USED ACCORDING TO TERMS OF SUBSCRIPTION