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GEOG 203 Midterm 1 Review.doc

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McGill University
GEOG 203
Bruce Murphy

Midterm 1 ReviewGeography Enironmental Systems Midterm 1 ReviewLecture 1Earth has four spheresHydrosphere Earths water exists in the crust the atmosphere and on the surfaceBiosphere The intricate interconnected web that links organisms with their physical environmentLithosphere Earths crust and a portion of the upper mantleAtmosphere A thin gaseous veil surrounding the earth held to the planet by the force of gravityOpen system is open to its surroundings and a closed system is one that is shutoff to its surroundings Planet earth is a good example of a closed system as very little matter exits earth or enters earth from spacePositive feedback is when a response to a change is amplified and negative feedback is when the response is reducedAttributes of environmental systemsFunction Scale Feedbacks Equilibrium statesLecture 2Radiation emissionAll bodies that possess energy emit radiationTemperature is a measurement of how much internal energy a body hasThe higher the temperature of a body the more radiation it will emit and the shorter the wavelengthsRadiation receptionAbsorbed reflected if the surface is reflective and has a relatively hig albedo transmittedSun surface is 6000 degrees celsius and emits shorter wavelengths around 05umEarths surface is about 15 degrees and emits longer wavelengths at around 10umlambdamax2898TEarth orbit is eccentric meaning there is a perihelion January 4 closest to sun and aphelion July 4 farthest from sun accounts for a 02 difference in sunlight received 100000 year cycleEarth wobbles between 22 and 24 degrees tilt 41000 year cycleThe average insolation Incoming Solar Radiation from the sun when it is at its average distace is 1370 Wm2If averaged over an sphere an not a disk it is 342 Wm2 insolation varies over a curved surfaceSun is directly vetical over the equators at the equinoxes and over the tropic of capricorn or cancer 235 degrees on the solstices occur on the 2123 of March June September and December The daily net radiation is positive approximately south of the 40 degree latitude and tendsto be negative north of the 36 degree latitude Incoming minus outgoing radiationFour main layers of the earths atmosphereThermosphere 80km300km high energy low densityMesosphere 50km80kmStratosphere 18km50km contains ozone layerTroposhere Final layer or the atmosphere 90 of atmospheric mass supports lifeThe normal environmental lapse rate is 64 degrees centigrade1000 metresConsider if earth was a blackbody it would effecitively radiate at 15 degrees but its average is 18 degrees This is due to the greenhouse effect of gases in the atmosphereLecture 3Earths average albedo is 31 meaning 31 of the incoming shortwave solar radiation is reflected back to spaceSome average albedo valuesFresh snow 8095 grass 2530 water bodies 1060 forests 1020 cropsgrasslands 1020 asphalt 510Water bodies can vary greatly depending on their latitude if the sun is directly overhead more radiation is absorbed less albedo If the sun is low in the sky the water has a higher albedoEnergy transformations in the radiation budgetRadiative loss depends on the temperature of the bodySensible heat transfersurrounding soil air and water are heatedLatent heat transferUptake and release of energy as water changes phaseWith increasing cloud cover the prediction for the affect on albedo can be misleadingThick stratus clouds low to surface tend to generally cool because they reflect alot of the suns raysThin cirrus clous tend to let the suns rays pass through
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