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Chapter 4

GG101 Chapter 4 Notes.docx

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Department
Geography
Course
GG101
Professor
James Hamilton
Semester
Winter

Description
GG101 Chapter 4 Notes- Atmosphere and Surface Energy Balances Energy Esssentials  Solar energy heating Earth’s atmosphere and surface is unevenly distrubted by latitude, and fluctuates seasonally  Refer to: flow diagram of shortwave and longwave radiation  Transmission: the passage of shortwave and longwave energy through either the atmosphere or water o Shortwave: includes radiation inputs (UV light, visible light, and near-infrared wavelengths) o Longwave: OUTPUTS such as thermal infrared  Insolation Input: insolation is the single energy input driving the Earth-atmosphere system o Solar energy (watts per square metre) is distributed unevenly throughout the world o Insolation decreases poleward from about 25 degrees latitude in both North and South hem’s o Consistent daylength and high Sun altitude produce average annual values of 180-220 W/m^2 throughout equatorial and tropical latitudes o Greater insolation occurs in low-latitude areas due to lack of clouds: Sonoran, Saharn, Arabian, Gobi, Atacama, Namib, Kalahari, Australian  Scattering (Diffuse Radiation): the process of insolation encountering increasing density of atmospheric gases as it travels toward the surface; the downward component of scattered light o Atmospheric gases and physically interact with insolation o Gas molecules redirect radiation, changing direct of light movement WITHOUT altering wavelength o Rayleigh Scattering: The shorter the wavelength, the greater the scattering and vice versa  Small gas molecules in the air scatter shorter wavelengths of light  Thus, the shorter wavelengths of visible light- the blues and violets- scatter the most and dominate the lower atmosphere  A blue sky prevails because there are more blue than violet wavelengths in sunlight  A sky filled with smog and haze appears white b/c the larger particles associated with air pollution act to scatter all wavelengths of visible light  Refraction: a bending action where insolation passes through various mediums, shifting direction in speed o Think: a ray of light passing through a prism/crystal- rainbows are created this way (reflected at precise angles towards witness) o Mirage: an image that appears near the horizon where light waves are refracted by layers of air at different temperatures (and consequently of different densities) o The atmospheric distortion of the setting Sun iis also a product of refraction  Refraction also causes the sun’s image to appear 4 minutes before it rises above horizon  Albedo and Reflection o Albedo: the proportion of K that is reflected or scattered from the surface and/or the atmosphere o Reflection: a portion of arriving energy bounces directly back into space without being absorbed or performing any work o Albedo: the reflective quality or intrinsic brightness of a surface (mirror vs dirt?)  i.e. dark colours have lower albedos, lighter colours have higher albedos o ERB- Earth Radiation Budget: sensors in satellites that measure Albedo concentration (19-38% in areas between tropics, and 80% near the polar regions)) o Earth and its atmosphere reflects 31% of all insolation when averaged over a year; comprised of clouds, land, ocean and reflections o Snow and ice also contribute to higher albedo o Albedo (reflective shortwave radiation/incoming shortwave radiation)*100%  24% absorbed in atmosphere, 31% reflected/scattered back to space, 45% reaches surface and is absorbed  Clouds, atmospheres and the atmosphere’s albedo o Cloud-Albedo forcing: an increase in albedo caused by clouds; yet clouds act as insulation, trapping longwave radiation from Earth and raising minimum temps o Cloud-greenhouse forcing: an increase in greenhouse warming caused by clouds o Eruption of Mount Pinatubo in the Philippines: caused 15-20 megatons of sulfur dioxide to be injected into the stratosphere; an average cooling of 0.5 degrees C was caused o Industrialization is producing a haze of pollution that is increasing the reflectivity of the atmosphere, including sulfate aerosols, soot and fly ash, and black carbon o Emissions of sulfur dioxide and subsequent chemical reactions in the atmosphere from sulfate aerosols  This pollution causes both atmospheric warming and surface cooling through reduction in insolation reaching ground and water surfaces (global dimming)  Absorption: the assimilation of radiation by molecules of matter and its conversion from one form of energy to another o Insolation in all forms that is NOT part of the 31% reflected from Earth’s surface and atmosphere is absorbed  Converted into longwave radiation or chemical energy by plants in photosynthesis o Warmer surfaces radiate more total energy at shorter wavelengths- the hotter the surface, the shorter the wavelengths that are emitted  Conduction, Convection and Advection o Conduction: molecule-to-molecule transfer of heat energy as it diffuses through a substance  As molecules warm, their vibration increases, causing collisions that produce motion in neighbouring molecules  Solids, liquids and gases conduct sensible heat directionally from areas of higher temp to those of lower temp  Example: heating of surfaces and overlying air, and soil temps o Convection: when physical mixing involves a strong vertical motion  Example: atmospheric and oceanic circulation, air mass movements and weather systems, internal motions deep within Earth that produce a magnetic field and crust movement o Advection: horizontal motion dominates  Example: horizontal movement of winds from land to sea and back, fog that forms and moves to another area, and air-mass movements from source regions o Solid, Liquids and Gases: remember particle theory…evaporation Energy Balance in the Troposphere  The earth-atmosphere energy system budget naturally balances itself in a steady-state eq’m  The greenhouse effect and atmospheric warming o Some of Earth’s
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