ATOC 1060 1st Edition Lecture 5 Outline of Last Lecture Outline of Current Lecture I. Black Body RadiationII. Cause of Greenhouse Effect III. Cloud influence on ClimateCurrent LectureI. Black Body RadiationBlackbody: an object which absorbs and emits radiation perfectly. The final radiation emitted (type and amount) is determined by the temperature. We see colors because lights from a certain wavelength get reflected/scattered into our eyesLight of all wavelengths are reflected into our eyes.-White is not a color-When we see black, no light of any wavelength is being reflectedBlack bodies absorb and emit all radiationAnything with a temperature greater than 0K emits radiationBlack body emissions depend on temperatureWein’s Law =2898(umK)/T(K)Sun=6000K so =2898/6000=0.48umEarth=300K so =2898/300=9.7umThese 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. Sun has higher temperature than earth so sun emits peak radiation at a smaller wavelength (higher frequency) than earthSun’s Peak radiation visible light 480nmEarths Peak radiation infrared radiation 9700nmyyyTotal Energy: Add up radiation at all wave lengths Stephan-Boltzmann Laweverything emits radiationcolder items emit less radiation than warmerExample: cold blooded snake emits less radiation than warm blooded person cold earth emits less radiation than warm sunBlackbody’s that are hotter emit more radiationNegative Feedback---- The “Planck Feedback”When earth warms the emission of outgoing long wave radiation increases Additional long waveemission cools and tends to reduce warming.II. Greenhouse Effect1. Suns radiation passes through atmosphere and is absorbed at the surface2. Surface is warmed by the sun and emits long wave radiation3. Atmospheric greenhouse gases absorb surface radiation and emit it back to the surface. The additional radiation back warms the surface1. Greenhouse gasses do not absorb shortwave radiation2. Do absorb and re-emit infrared or long wave radiation – warming the surfaceCarbon Dioxide: Strongly absorbs outgoing long wave radiation due to a bending modeWater Vapor: Strongly absorbs outgoing long wave radiation due to a rotation modeNitrogen gas is not a greenhouse gas.III. Clouds-Albedo of Earth 0.3 - Without clouds Albedo of Earth 0.1Carbon Dioxide and water vapor absorb 100% of outgoing long wave radiation at many wavelengths.Greenhouse gasses absorb and emit long wave radiation but not at all wavelengths.Atmosphere is made ofNitrogen=78Oxygen=21Argon= 0.9Solar energy during the day is reflected off of clouds back into spaceWarm air is trapped between clouds and the Earth’s surface at nightTherefore, a cloudy night is warmer than a clear nightGreenhouse Effect with Clouds-Surface is warmed by the sun and emits long wave radiation-clouds absorb surface radiation and emit it back towards the surface the additional backradiation warms the