Chapter 4 Notes - Chapter Four Atmosphere and Surface...

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Chapter Four: Atmosphere and Surface Energy Balances Energy Essentials The flows of energy are manifest in swirling weather patterns, powerful oceanic currents, and the varied distribution of vegetation. Specific energy patterns differ for deserts, oceans, mountaintops, plains, rainforests, and ice covered landscapes. The presence or absence of clouds may make a 75% difference in the amount of energy that reaches the surface because clouds reflect incoming energy. Energy Pathways and Principles Solar energy heats Earth’s atmosphere and surface is unevenly distributed by latitude, and fluctuates seasonally. Transmission – the passage of shortwave and long wave energy through either the atmosphere or water. Our budget of atmospheric energy comprises shortwave radiation inputs and long wave radiation outputs that pass through the atmosphere by transmission. Insolation Input – single energy input driving the Earth-atmosphere system. Decreases pole-ward from about 25 degrees latitude in both the Northern and Southern Hemispheres. Greater insolation occurs in low latitude deserts worldwide because of frequently cloudless skies. Scattering (Diffuse Radiation) Insolation encounters an increasing density of atmospheric gases as it travels toward the surface. Atmospheric dust and gases physically interact with insolation. The gas molecules redirect radiation changing the direction of the lights movement without altering its wavelengths. This phenomenon is known as scattering. ^ It represents 7 percent of the earth’s reflectivity or albedo. Dust particles pollutants, ice, cloud droplets, and water vapor produce further scattering. Blue Sky – Rayleigh scattering. The shorter wavelength, the greater the scattering and the longer wavelength the less the scattering. Small gas molecules in the air scatter shorter wavelengths of light. The shorter wavelengths of visible light—blues and violets—scatter the most and dominate the lower atmosphere. A sky filled with smog and haze appears almost white because the larger particles associated with air pollution act to scatter all wavelengths of visible light. The angle of the suns rays determines the thickness of atmosphere they must pass through in order to reach the surface. Direct rays from overhead experience less scattering and absorption than do low oblique angle rays that must travel farther through the atmosphere. Insolation from the low altitude sun undergoes more scattering of shorter wavelengths, leaving only the residual oranges and reds to reach the observer at sunset or sunrise.
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