lab 4.docx - The atmosphere exercises a significant...

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The atmosphere exercises a significant influence on the Earth’s energy system, filtering the  types of shortwave energy that enter the top of the atmosphere and delaying the release of  longwave energy from the Earth back to outer space. Atmospheric temperature and pressure  are determined to a large part by this balance of energy in the lower atmosphere and at the  Earth’s surface. The global pattern of pressure and wind belts result from this balance of energy at the Earth’s surface. Additionally, variations in humidity and temperature determine the  stability of our atmosphere and contribute to the formation of distinct weather patterns. The Earth’s energy budget is driven by solar energy entering the atmosphere as   shortwave  radiation , intense energy that peaks in the visible wavelengths of light.   The amount of solar  radiation reaching the Earth’s atmosphere varies slightly with the Earth’s orbital distance from  the Sun and fluctuations in solar activity.   The most recent information provided by NASA  indicates that the total energy coming from the Sun varies by only 0.1% during typical periods of solar fluctuation, and varies between 0.2% and 0.6% over several centuries.   The term   solar  constant   refers to the short-term average amount of solar energy received over the course of a  year, which is currently estimated to be approximately 1366 W/m 2 . Understanding the interaction of shortwave solar radiation with the Earth’s atmosphere  is critical to understanding all other atmospheric processes. Only 28% of all incident  shortwave energy makes it directly through the atmosphere to the surface of the planet  without being reflected or absorbed. Another 28% is either reflected or scattered by the  atmosphere (7%) and clouds (21%).  An additional 24% is absorbed by the atmosphere  (18%), clouds (3%), and stratospheric ozone (3%). Not all of the shortwave energy that does make it to the surface is absorbed. The  proportion of incident energy that is reflected by a surface is referred to as  its  albedo . Variations in albedo typically are controlled by surface texture and color.   High albedo substances are those that are highly reflective and tend to be smooth in  texture and light in color. Low albedo substances are those that reflect a smaller portion  of the incident energy, instead absorbing more of the shortwave radiation. These  substances tend to be dark in color and rough in texture. On average, 3% of the incident energy is reflected back into space from the surface of the Earth. This reduces the total  share of direct shortwave energy absorbed by the Earth's surface to 25%.
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  • Summer '14
  • Polar Front, adiabatically. Rising

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Christopher Reinemann
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