地球大气圈变化英文版.ppt

Evolution of the AtmosphereReview of last lectureThe modern climatology(meteorology)was born in the 1940s(a very young science!),but has been growing very fast!Now we have a global observational network with many satellites,ships,radars and surface stations,as well as very comprehensive prediction models running on the worlds fastest supercomputers.The current status of weather and climate predictions:(1)weather prediction good to 10 days,(2)tropical cyclone prediction good in track but not in intensity,(3)climate prediction good to two seasons,(4)climate change projections have a 3-fold difference in magnitude.The main reasons of the difficulties in weather and climate predictions:(1)Teleconnection problem,(2)Feedback problem,and(3)Subgrid-scale problem.Some basic conceptsUnits of measurementScientific notationStandard units of measurementSI(System International)QuantityNameUnitsSymbolLengthmetermmMasskilogramkgkgTimesecondssTemperatureKelvinKKDensitykilogramkg/m3kg/m3per cubic meterSpeedmeter perm/sm/s secondForcenewtonm.kg/s2NPressurepascalN/m2PaEnergyjouleN.mJPowerwattJ/sWScientific Notationnanoone-billionth10-90.000000001microone-millionth10-60.000001millione-thousandth 10-30.001centione-hundredth10-20.01decione-tenth10-10.1dekaten10110hectoone hundred102100kiloone thousand1031000megaone million1061000000gigaone billion1091000000000yotta1024The UniverseThe Universe is made up of voids and filaments,that can be broken down into superclusters,clusters,galaxy groups,galaxies,and subsequently into stars and their constituents(e.g.our Solar System).Hubble(2012)vieweachlightspeckisagalaxysomeoftheseareasoldas13.2billionyearstheUniverseisestimatedtocontain200billiongalaxies.Our Milky Way galaxyOursolarsystemisintheOrionarm,andweareabout25,000lightyears(2.5X1017miles)fromtheverycenteroftheGalaxy.Life cycle of the Sun and EarthTheearthwillbeinhabitableforanother0.5billionyears,ifweprotectitwellenough.Afteranother1billionyears,alloceansandriverswillhavecompletelydisappeared.Themeanglobaltemperaturewillreach160F.Formation of the Earth4.6billionyearsago,aspartofthebirthofthesolarsystemEarths first AtmosphereTopic of much debateProbably H and He,no oxygenNo oceansNo magnetic field to deflect solar winds and cosmic rays Differentiation of the Earth Cooled enough to form crust,heavily populated with volcanoesFormation of magnetic field that deflects the solar wind and cosmic raysIncreasing volcano activity,releasing gases into atmosphereEarths Second AtmosphereAround 4-3.8 billion years agoComposition similar to gases released from volcanoes(CO2,water vapor,nitrogen)Large concentration of gases in the atmosphere(100 times of todays)Greenhouse effect keeps the earth from freezingEarth Begins to CoolWater condenses to form oceansCarbon Dioxide dissolves into oceans eventually forming carbonates Nitrogen becomes major component of the atmosphereLife and oxygenAround 3.5 billion years ago cyanobateria were known to be carrying out photosynthesis CO2+H2O+sunlight=organic compounds+O2Eukaryotes capable of respiration emerge around 2.5 billion years ago.Photosynthesis becomes more efficient Increased oxygen concentration,around 1%of atmosphere,produced the ozone layerLife emerges outside of the oceans.Formation of terrestrial plants lead to atmospheric saturation of oxygenEarths third atmosphere(current)Reached around 400 million years agoConsisting of gases,water droplets(clouds/precipitation)and aerosolsFormation of the continents and ocean basins225 million years ago from Pangaea(the super continent)Permanent gases and variable gasesResidencetime:TheamountoftimeagasisintheatmosphereThepermanentgases:gaseshavinglongresidencetimes(N2=42,000,000y,O2=5,000y),99.999%oftotalatmospheremassThevariablegases:Gasesgenerallyhavingshorterresidencetimes(H2O=10days,CO2=150y).Importance of the Variable GasesCO2 and water vapor are the major greenhouse gasesWater can exist in all three phases(vapor,liquid,ice)on Earth.The released latent heat during phase changes of water drives global atmospheric circulation and many weather systems(e.g.hurricanes).O3 protects us against harmful ultraviolet radiationMontrealProtocoltobanfreonEarths climate historyTemperature variation during the past 2.4 billion years-The ice agesAn ice age is a long interval of time(106 to 107 of years)when global temperatures are relatively cold and large areas of the Earth are covered by continental ice sheets and alpine glaciers.At least 5 ice ages have occurred throughout Earths history.Currently,we are living in an ice age!Typically develop slowly,but end more abruptly.Variations within an ice age:Abrupt climate change and tipping pointSome examples of tipping pointsVariations within an ice age:The 100,000-year glacial cyclePossible causes:Change in atmospheric composition(e.g.CO2,CH4)Change in earths orbit(e.g.Milankovitch cycles)Motion of tectonic platesChange in solar outputThe little ice age(1350AD-1850AD)Evolution of the atmosphereThe standard units of measurements(SI)Earths three atmospheres:1st:4.6 billion years ago,H,He Transition:formation of magnetic field,volcano activities 2nd:4 billion years ago,CO2,H2O,N2 Transition:emergence of life,formation of ocean 3rd:400 million years ago,O2 Important event:formation of seven continentsWhat is the residence time?What is the difference between the permanent and variable gases?Name 3 of each.What are the most and second most abundant gases?Given that variable gases are so rare,why are they considered at all?How are CO2 and O3 changing?Earths climate history:ice ages(at least 5 have occurred so far.Were in an ice age!),100,000-year cycle,little ice age(1350-1850AD)Works citedhttp:/ase.tufts.edu/cosmos/view_picture.asp?id=850http:/www.waterconservation.co.za/2010/10/26/theres-never-been-a-better-time-to-start-harvesting-rainwater/