Popular in Earth: our habitable planet
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This 0 page Class Notes was uploaded by Bruce Kwon on Sunday February 28, 2016. The Class Notes belongs to GEOG-G105 at Indiana University taught by Bruce Douglas in Spring 2016. Since its upload, it has received 21 views. For similar materials see Earth: our habitable planet in Geology at Indiana University.
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Date Created: 02/28/16
11 How the earth differ from other planets Primarily because of the position in relation to the sun Average surface temperature of earth is 15 degrees C usually between 50 C and 50 C Life is concentrated towards the equator Formula of photosynthesis C02g H20 gtlightgt CH20 02g this process if called quotfixing carbonquot or the primary process Animals cannot x carbon therefore needs to consume primary producers Humans have direct affect in vegetation production through irrigation of land domesticated animal graze etc However primary production is determined by the movement of air and water over the surface of earth 12 Energy from the sun Solar Flux solar irradiance solar constant amount of solar energy that falls on a surface at right angle to the sun39s rays Average amount of solar ux effective solar ux 343 W m392 However about 30 is re ected back into space Albedo the fraction of incoming solar radiation that is re ected Earth39s atmosphere receives about 70 of the solar ux 240 W m392 Intensity of solar radiation at Earth39s surface is lower at high latitudes Also depends on the angle of the rays with respect to the surface The more oblique the angle 0 the larger the surface area to which rays can spread The greater the thickness of atmosphere through which the rays will travel If earth39s axis had no tilt Angle of the rays of the noonday would remain constant 0 Night and day would always be the same length each 12 hours long everywhere in the world Due to earth39s axis tilt 234 deg Latitude at which the noonday sun is overhead migrates between 234 N tropic of cancer and 234 S tropic of Capricorn Passes the earth twiceyear Equinox length of day and night are equal 0 Causes of seasons Cause of seasons 0 When tilting toward sun Tropic of Cancer 21 June northern summer solstice southern winter solstice No tilt Equator 21 Sept northern autumn equinox When tilting away from the sun Tropic of Capricorn 21 Dec northern winter solstice southern summer solstice No tilt Equator 21 March northern spring equinox Aphelion 152 x 10quot6 km Perihelion 147 x 10quot6 km Milankovich Cycle Eccentricity Precession tilt Eccentricity ellipticity due to varying gravitational attraction of the sun and other planets exaggerates the seasons Precession clockwise movement of the axis Tilt change of the angle of the poles with respect to the center of the earth the greater angle of tilt greater difference between winter and summer Some typical albedos Fresh snow and sea ice 8090 Clouds 55 Thawing snow 45 Desert 35 Grassland 25 33 Forest bare 50 rock cities 10 20 Water high sun elevation gt lt 5 40 deg Water low sun elevation 10 0 deg 50 121 The Atmosphere a protective lter Electromagnetic spectrum Gamma rays Xrays Ultraviolet Visible Infrared Microwaves Radio waves The process of radiation is different from re ection Energy is not absorbed and reradiated Energy bounce off with it39s frequency and wavelength unaffected StefanBoltzmann law 0 Any body above absolute zero emits radiant energy 0 The energy emitted per unit area per unit time is proportional to the fourth power of the temperature in Kelvin Remember that the kelvin scale starts at absolute zero or 27315 C so 27415 K Atmospheric window ranges from 813 micrometers area where there is relatively less energy absorption Greenhouse effect energy reradiates back towards the earth39s surface This is what keeps the earth39s average surface temp to 15 C Clouds absorb and reradiates ongwave radiation and they play a very important role in the greenhouse effect Unlike gases they also strongly affect the earth39s albedo The atmosphere is primarily heated from below due to the bouncing of the ongwaves The net atmosphere radiation budget is in balance so the earth is neither cooling norhea ng While the dominant cause of present global warming is human activity climatic changes in the 20th to let centuries can only be fully explained when both natural and anthropogenic effects are taken into account Forcing function external input that drives or forces much of the activity in the system radiation from the sun Sensitivity the size of the response of a system to a forcing of given magnitude response of the earth39s surface temp to a change in solar forcing Climate sensitivity change in average surface temp resulting from a given change in atmospheric C02 concentration 13 The Earth39s Surface Temperature Pattern The redistribution of solar energy from low to high latitudes in responsible for motions of atmosphere and oceans It is what controls diversity and habitability on ea h Speci c heat the amount of heat required to raise the temperature of 1 gram of substance by 1 C Because the speci c heat of water is higher than sand the continents change temperature more than the oceans over the course of seasonal changes Properties of water that are important for climate 0 Water can exist as gas liquid or solid 0 It39s speci c heat is 418 x 10quot3J kgquot1 Cquot1 highest of all solids and liquids except ammonia lt39s latent heat of fusion amout of heat needed to convert 1 kg of ice to water is 33 x 10quot5J kgquot1 is the highest of all solids and liquids except ammonia