Orbiting above the Earth, an astronaut can look down on our home and see the thin blue ribbon that rims our planet. That transparent blanket – our atmosphere – makes life possible. It provides the air we breathe and regulates our global temperature. And it contains a special ingredient called ozone that filters deadly solar radiation.The AtmosphereThe gaseous area surrounding the planet is divided into several spherical strata separated by narrow transition zones which is the atmosphere. (Graedel 1998) The upper boundary at which gases disperse into space lies at an altitude of approximately 1000 kilometers above sea level. (Graedel 1998) More than 99% of the total atmospheric mass is concentrated in the first 40 km from Earth’s surface. (Graedel 1998) Atmospheric layers are characterized in chemical compositions that produce variations in temperature. (Graedel 1998) Here is a graph of the different layers in the atmosphere: TroposphereThe troposphere is the atmospheric layer closest to the planet and contains the largest percentage of the mass of the total atmosphere. (Garcia 1994) It is characterized by the density of its air and an average vertical temperature change of 6 degrees Celsius (C) per kilometer. (Graedel 1998)Temperature and water vapor content in the troposphere decrease rapidly with altitude. Water vapor plays a major role in regulating air temperature because it absorbs solar energy and thermal radiation from the planet's surface. (Graedel 1998) The troposphere contains 99 % of the water vapor in the atmosphere. Water vapor concentrations vary with latitudinal position. They are greatest above the tropics, where they may be as high as 3 %, and decrease toward the Polar Regions. All weather phenomena occur within the troposphere, although turbulence may extend into the lower portion of the stratosphere. (Graedel 1998) Troposphere means "region of mixing" and is so named because of vigorous convective ...
