Chapter 4 Outline

Chapter 4 Outline - Chapter 4: Atmosphere and Surface...

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Chapter 4: Atmosphere and Surface Energy Balances Introduction Earth’s outpus of reflected light/emitted infrared energy fr atmosph/surface envt counter input of insolation; input + output determine net energy available to perform work; Energy Essentials Land/water surfaces, clouds, atmos gases, dust intercept solar energy; specific energy patterns diff for deserts, oceans, mtntops, plains, rain forests, ice-covered land; clouds reflect incoming enrgy Energy Pathways and Principles Transmission - passage of shortwave/longwave energy thru atmos/water; our budget of atmos’ic energy comprises s-wave radiation inputs (UV, visible, ~infrared light) & l-wave radiation outputs (thermal infrared) tht pass thru atmos by transmission Insolation Input Insolation- single energy input driving Earth-atmos sys; decr poleward fr 25°lat in N/S Hems; constant daylength/high Sun alt produce avg annually 180-220 W/m 2 thruout equatorial/tropical lats; greater insolation of 240-280 W/m 2 occurs in low-lat deserts worldwide b/c ~cloudless skies there Scattering (Diffuse Radiation) Insolation meets incr’g density of atmos gases/dust as travels surface; gas molcs redirect radiation, changing direction of light’s movement w/o altering its wavelengths - this= scattering , represents 7% of Earth’s reflectivity/ albedo ; also due to pollutants, ice, cloud droplets, water vapor Rayleigh scattering principle - shorter wavelength= greater scattering, longer wavelength=less; shorter wavelengths visible light (blue/violet) scatter the most, dominate lower atmos; thus blue sky; angle of Sun’s rays determines thickness of atmos they must pas thru to reach surface: Direct/overhead rays less scattered/absorbed b/c travel sml distance; reds/oranges at sunset b/c shrter wavelengths scatter much; sme incming insolation diffused by clouds/atmos, goes Earth as diffuse radiation - dwnwrd component of scattered light; multidirectional, casts shadowless light to ground Refraction As insolation enters atmos, travels thru many mediums- thus change of speed/shift in direction, a bending action called refraction ; eg light thru prism to get spectrum; or mirage - image tht appears near horizon where light waves refracted by lyrs of air at diff temps on hot day Refraction adds 8 min daylight-4 min sunrise, 4 min -set; degree of refraction cont’ly varies w/atmos temp, moisture, pollutants, so cannot predict exact time of visible sunrise/set w/in thse 4 mins Albedo and Reflection Some arriving energy bounces directly back to space- reflection process; albedo - reflective quality/ intrinsic brightness of surface- impt control over amt of insolation available for absorption by a surface; albedo stated as % of insolation that is reflected- eg. 0% total absorption W/visible wavelengths, darker colors= lower albedos, lighter colors= higher; on water surfaces, lower angles of solar rays= greater reflection than higher angles; smooth surfaces incr albedo- opp of
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This note was uploaded on 06/24/2008 for the course GEOG 1 taught by Professor Okin during the Fall '06 term at UCLA.

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Chapter 4 Outline - Chapter 4: Atmosphere and Surface...

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