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UNC-Chapel Hill GEOG 111 - Solar and Terrestrial Radiation

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GEOG 111 1st Edition Lecture 3 Outline of Last Lecture I. Elements of a forecast (cont’d)II. Forecast skilla. Accuracyb. Factors involvedIII. Specificity of a forecastIV. Solar and Terrestrial RadiationOutline of Current Lecture I. Solar and Terrestrial RadiationII. Radiation Lawsa. Stefan-Boltzmann Lawb. Weins LawIII. SunspotsIV. Earth-atmosphere influences on radiationa. Absorptionb. Reflectionc. ScatteringCurrent LectureI. Solar and Terrestrial Radiationa. Radiation is energy that comes in a wide variety of forms (the electromagnetic spectrum)b. Discriminated on the basis of wave length: gamma xrays UV visible light infrared radiation microwaves radio wavesi. Wavelength is the distance from one peak to anotherii. Short end- powerful gamma rays that can go through solid materialsiii. Long end- microwaves and radio waves that have long wavelengths and are far less powerful II. Radiation LawsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Stefan-Boltzmann Law- the hotter a body is the more radiation it emitsi. Blue is shorter part of the wavelength so it’s the hottest part of the flameii. E = Stefan-Boltzmann constant * temperature ^4b. Weins Law- the wavelength of maximum emissioni. The sun peaks at a shorter wavelength than the Earth which ensures that it’s hotter1. Temperatures generally decrease with increasing height above the earth, therefore higher clouds are colder than lower clouds and the eartha. Infrared satellite images help to discern cloud heights ii. Likewise, blue stars are hotter and red stars are coolerIII. Sunspotsa. Solar constant- solar output is relatively constant over timeb. When solar radiation does vary we attribute it to sunspot activityi. Sunspots- storms on the surface on the sunii. More sunspots  more solar radiation  higher temperature on Earth’s surfaceIV. Earth-atmosphere influences on radiationa. Three important processesi. Absorption- to assimilate or take in energy1. The atmosphere absorbs some of the radiation from the sun2. Example: the ozone (part of the stratosphere, above the atmosphere) is very effective at absorbing ultraviolet radiation from the sun which creates a warming effect3. Example: clouds made of microscopic sized water droplets or ice crystalsat high temperatures4. Greenhouse gases- gases such as CO2 and water vapor that are very effective in absorbing infrared (long wave) radiation emitted from the Earth’s surface. This warms the atmosphere up and re-radiates more energy back to the surfaceii. Reflection- the temperature of the reflecting object is unchanged1. Albedo (A)- describes the overall reflectivity of the Earth’s surfacea. A = (outgoing K/incoming K) x 100%b. Where K is reflected radiationc. Light colors have high albedos and dark colors have low albedosd. Example: fresh snow has the highest albedoe. Example: this is why people where dark colors in the colder months and light colors in the warmer monthsiii. Scattering- redirecting part of the visible light spectrum1. As visible light comes into the atmosphere, blue light is cycling rapidly and reds are cycling slowly2. Blues are more likely to collide with an atmospheric particles and be redirected (scattered)3. This is why blue light is preferential the sky is blue in an average midday skya. The color of the sky indicates the amount of scattering taking place4. Why does volcanic dust make sunsets red/orange? About six months after an eruption volcanic dust covers the atmosphere. This dustcontains much larger particles than the atmospheric molecules that are normally present. This dust increases the possibility that the reds, oranges and yellow light (longer wavelengths of the visible light spectrum) are more likely to collide and scatter, thus making a red


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