GEOL 108Lg 1st Edition Lecture 16Outline of Last Lecture- Finish River Morphology- Hydrographs- Floods and Flood Frequency- Erosion and Siltation- Groundwater and Groundwater Flow- Overdrafts- ContaminationOutline of Current Lecture- Weather vs. Climate- Greenhouse EffectCurrent LectureEa r t h ’s Cl i mat P t. IChanging storm frequency & damage associated with storms - due to climate changeEvents that cause a lot of damage...due to changing climate? Single storm vs. ClimateWeather vs. ClimateWeather: natural phenomena within the atmosphere at a given time (seconds, hours, days) Climate: the average weather conditions and their range of variability, over a long period of time (~30 years or more) - geology may discuss in terms of millions of yearsObviously these two are linked, yet distinctEarth is the Goldilocks Planet (just the right climate for life, habitable) - but why?We have to think about what determines climate:1. temperature determines ENERGY - climate is about energy and energy balanceEarth’s Climate is determined by ENERGY (from the sun)Principle of Radiative Balance: We (the earth and atmosphere) receive heat energy from the sun, but our planet/atmosphere has to radiate the same amount of heat back into space or we would completely overheat.Ra d iat iv e Ba l a n c e Eq u ati o n-->BALANCERadiative energy of the sun in relation to radiative energy of the planet into space. What is the light from the Sun?Electromagnetic radiation - all light is made up of photons - they behave like particles (like mass) and like waves (no mass, just propagated energy).Si n g l e Slit a n d t h e D o ub le Slit P at t e r n : used to prove that light behaves like a wave.Wave speed = (frequency - how often the crests come) x (wavelength)Photons always travel at the same speed - the speed of light (c), at least in a vacuumAs you change frequency or wavelength, you must change the other in responseThe amount of energy associated with different wavelengths of light changesRed Light v. Blue LightEle c t r o mag n et i c S p e c t r u mWavelengths of different types of light from Gamma Rays to Radio WavesBlack Body RadiationA black body is a hypothetical body consisting of a sufficient number of molecules absorbing and emitting electromagnetic radiation in all parts of the electromagnetic spectrum so that: a. all incident radiation is completely absorbed; andb. in all wavelengths bands and in all directions, maximum possible emission is realized.Although a blackbody does not really exist, we will consider the planets and stars (including the earth and the sun) as blackbodies. Even though by definition, they are not perfect blackbodies, for the sake of understanding and simplicity we can apply the characteristics of blackbodies to them.According to the above definition, a blackbody will emit radiation in all parts of the EM spectrum, but by intuition, we know that one will not radiate in all wavelengths equally. So the first thing we would like to know about blackbody radiation is in what wavelengths is radiation emited primarily. Secondly, we know that all blackbodies do not radiate energy at the same rate, certainly shown by the sun's power compared to that of the earth. Therefore, itwould be beneficial to know something about the rate of blackbody emission. Fortunately for us, we can answer both questions knowing only one characteristic of an object -- temperature.Wien's Displacement LawWien's displacement law says that the wavelength of the maximum emitted radiation is inversely proportional to the absolute (°K) temperature. If we plug in the temperatures of the earth and the sun, we will see that lambda max is 10µm and .49µm, respectively. Whereas theearth emits mostly infrared radiation, the sun emits mostly visible light. In fact, 43% is visible, 37% is near infrared and only 7% is ultraviolet. Wien's law allows us to determine temperatures of other stars depending on its color. Something that glows blue hot is much warmer than one that glows red hot.Diferent wavelength (or diferent frequency) of solar light and infrared light have an efect.1. About 70 to 75% of the solar radiation passes through the atmosphere and reaches the Earth2. This solar radiation is absorbed on the Earth surface, which warms up the Earth surface.3. When a body is warmer than its environment, it emits infrared radiation. The is also true for the warmed up surface of the Earth: The surface of the Earth emits infrared radiation 4. Because infrared radiation has a diferent wavelength than solar radiation, its transmission behaviour through the atmosphere is diferent: 15-30% will be transmitted and 70 to 85% will be reflected back to the Earth. This leads to a further increase of temperature on Earth.The G r e e nh o us e Ef f e c tThe greenhouse efect refers to circumstances where the short wavelengths of visible light from the sun pass through a transparent medium and are absorbed, but the longer wavelengths of the infrared re- radiation from the heated objects are unable to pass through that medium. The trapping of the long wavelength radiation leads to more heating and a higherresultant temperature. Besides the heating of an automobile by sunlight through the windshield and the namesake example of heating thegreenhouse by sunlight passing through sealed, transparent windows, the greenhouse efect has been widely used to describe the trapping of excess heat by the rising concentration of carbon dioxide in the atmosphere. The carbon dioxide strongly absorbs infrared and does not allow as much of it to escape into space. When incoming solar energy is not evenly distributed, the greenhouse efect happensBasic physical principles are what keeps the climate just rightIncoming Solar Energy not evenly distributedResult: convective heat transport from equator to poles through air and oceansW a y s o f Tra n s fe rr i n g Ene r gy-Radiation-Convection-ConductionA tm o s ph e r ic Ci r c u lat i o nIntense radiation at the equator warms the air, it rises - lower pressure - condensation - clouds - rain’Other problems:Depletion of aquifiersOgallala Aquifier – being depleted