GEOG 111 1st Edition Lecture 3 Outline of Last Lecture I Elements of a forecast cont d II Forecast skill a Accuracy b Factors involved III Specificity of a forecast IV Solar and Terrestrial Radiation Outline of Current Lecture I Solar and Terrestrial Radiation II Radiation Laws a Stefan Boltzmann Law b Weins Law III Sunspots IV Earth atmosphere influences on radiation a Absorption b Reflection c Scattering Current Lecture I Solar and Terrestrial Radiation a 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 waves i Wavelength is the distance from one peak to another ii Short end powerful gamma rays that can go through solid materials iii Long end microwaves and radio waves that have long wavelengths and are far less powerful II Radiation Laws These 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 emits i Blue is shorter part of the wavelength so it s the hottest part of the flame ii E Stefan Boltzmann constant temperature 4 b Weins Law the wavelength of maximum emission i The sun peaks at a shorter wavelength than the Earth which ensures that it s hotter 1 Temperatures generally decrease with increasing height above the earth therefore higher clouds are colder than lower clouds and the earth a Infrared satellite images help to discern cloud heights ii Likewise blue stars are hotter and red stars are cooler III Sunspots a Solar constant solar output is relatively constant over time b When solar radiation does vary we attribute it to sunspot activity i Sunspots storms on the surface on the sun ii More sunspots more solar radiation higher temperature on Earth s surface IV Earth atmosphere influences on radiation a Three important processes i Absorption to assimilate or take in energy 1 The atmosphere absorbs some of the radiation from the sun 2 Example the ozone part of the stratosphere above the atmosphere is very effective at absorbing ultraviolet radiation from the sun which creates a warming effect 3 Example clouds made of microscopic sized water droplets or ice crystals at high temperatures 4 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 surface ii Reflection the temperature of the reflecting object is unchanged 1 Albedo A describes the overall reflectivity of the Earth s surface a A outgoing K incoming K x 100 b Where K is reflected radiation c Light colors have high albedos and dark colors have low albedos d Example fresh snow has the highest albedo e Example this is why people where dark colors in the colder months and light colors in the warmer months iii Scattering redirecting part of the visible light spectrum 1 As visible light comes into the atmosphere blue light is cycling rapidly and reds are cycling slowly 2 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 sky a The color of the sky indicates the amount of scattering taking place 4 Why does volcanic dust make sunsets red orange About six months after an eruption volcanic dust covers the atmosphere This dust contains 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 tinted sky
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