SCIENCE

• The atmosphere of the earth is the layer of gases (commonly called air) that surrounds the earth and creates an inhabitable environment, maintains temperature, causes weather, and protects its inhabitants from solar radiation
• Layers of the Earth's Atmosphere


  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
• Troposphere


  Lowest layer of the atmosphere, where we live. It extends up to 5 to 10 miles (8 to 15 km) above the surface. It is the densest layer, containing more than half the volume of total air. Most of the atmospheric water vapor and dust are found here. This is where all the weather that we experience occurs, as clouds are formed here. The temperature falls as we get higher up, and is the lowest at the tropopause that acts as the boundary between this layer and the next. This is where Earth's jet stream is found.
• Stratosphere


  Lies just above the troposphere, extending up to 31 miles (50 km) high. It is the part of the atmosphere that contains the ozone layer, which is essential for our survival as it blocks the harmful UV rays of the Sun from reaching us. Unlike the troposphere, in this layer, the temperature increases as we go higher. Jet aircraft and weather balloons fly in this layer as there is less turbulence. The stratopause acts as the boundary between the stratosphere and the mesosphere.
• Mesosphere


  Extends from just above the stratosphere to 53-62 miles (85-100 km) high. It is the coldest layer of the atmosphere, with the temperature dropping to its lowest at the boundary between the mesosphere and thermosphere, called the mesopause. Nothing is known about this layer except that meteoroids burn up here, preventing them from reaching the Earth's surface.
• Thermosphere


  Extends from the mesopause to about 372 miles (600 km) high. It is the hottest layer of the atmosphere, but the air density is so low that the high temperature cannot be felt at all. Most of the thermosphere is actually considered part of outer space due to this low air density. This is where the Aurora Borealis and Aurora Australis occur, caused by collisions between charged particles from space and the air molecules.
• Exosphere


  Extends from the upper boundary of the thermosphere, between 310 and 620 miles (500 and 1,000 km). Its lower boundary is called exobase or exopause, and this is the altitude above which atmospheric temperature remains almost constant. The exosphere is the least dense layer of the atmosphere, comprised of mostly helium and hydrogen.
• Satellites and space stations, like the International Space Station, orbit the Earth in the thermosphere
• Airplanes and other commercial aircraft fly in the troposphere
• The Kármán line, at 62 miles (100 km) above the surface, is often said to be the point at which outer space starts
• Ionosphere


  A layer of charged particles (ions) that stretches from 48 km above the surface to around 965 km, spanning the mesosphere, most of the thermosphere, and some parts of the stratosphere. It is important for radio communications and is responsible for auroras. Its size varies with daytime and nighttime.
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• Air pressure changes with altitude
• Air is all around us, but we cannot see it
• Gravity from the Earth pulls air down - this is called air pressure
• We don't feel this pressure because our bodies push an equal amount of pressure outward
• This graph shows how air density and air pressure changes with altitude (the distance above sea level)
• Barometers are used to measure air pressure in milibars
• This graph shows how air pressure changes with altitude (the distance above sea level) as one moves upward in the atmosphere
• The density of air is computed based on the mass of air molecules, divided by the volume of air
• Density and pressure change similarly with height
• The atmosphere is divided into different layers depending on how temperature changes
• This graph shows how temperature changes with altitude
• Near the Earth's surface, air gets cooler the higher you climb. As you climb a mountain, you can expect the air temperature to decrease by 6.5° C for every 1000 meters you gain. This is called the standard (average) lapse rate
• If air temperature is 27° C at sea level as shown, you can expect it to be around 1° C at air altitude of 4000 meters because of the lapse rate
• Plan an Expedition


  You are going to climb Mount Audubon in Colorado today!
• When you leave your house at 2000 meters, the air temperature is 15° C. What is the temperature likely to be at the 4000 meter summit?