UW ATMS 211 - Stratospheric vs Tropospheric Ozone

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AssignmentsAssignmentsRead Ch 17: OzoneRead Ch 17: OzoneRead Ch 16: Global warmingRead Ch 16: Global warmingAnnouncements Announcements Poster: single grade for each pairPoster: single grade for each pairIncludes grade on annotated bibliographyIncludes grade on annotated bibliographyIndividual grade included based on your Individual grade included based on your evaluation of two other postersevaluation of two other postersWriting credit Writing credit ––if you expect to receive writing if you expect to receive writing credit, you should have an email from me. If you credit, you should have an email from me. If you do NOT, see me immediatelydo NOT, see me immediatelyAnnouncements Announcements Poster MakingTitle and authorsIntroConclusionsFIGURES/SKETCHES/TABLESBig fonts!~24pt for normal textGet poster paper ~4’x3’from bookstoreWhere are we?Where are we?Finished with past climateFinished with past climateLook at two current issuesLook at two current issuesOzone depletionOzone depletionGlobal warmingGlobal warmingPoster weekPoster weekFinal reviewFinal reviewToday Today ––Ozone Ozone •Stratospheric vs Tropospheric Ozone•Ozone depletion and the “ozone hole”•Ozone and Global Warming: How are they related and not?Reading: Chapter 17From the From the ““Global Warming SurveyGlobal Warming Survey””Statement:Statement:The ozone hole over Antarctica is a The ozone hole over Antarctica is a result of global warmingresult of global warmingTrueTrue4343FalseFalse23 23 DebatableDebatable1515OzoneOzone’’s Many Facess Many Faces•Ozone-3 oxygen atoms•What’s the big deal? Depends, ”which ozone”?•Measuring ozone and finding where its distributedOzone and OxygenOzone and OxygenMolecular oxygen is 2 oxygen atoms bonded together- stableOzone is 3 oxygen atoms bonded together – unstable – wants to get rid of extra OO3is more reactive than O2Vertical Distribution of OVertical Distribution of O33Most O3(90%) in stratosphere.Remaining 10% in troposphere.“Ozone layer” (15-30 km) is 3000 – 5000 ppb of O3.Surface O3~ 40 –100 ppb.Ozone is Good and BadOzone is Good and BadOzone is reactive oxidizer: damages plant and animal tissues—reduced crop yields, forest growth, lung capacityO3is a greenhouse gas: increased tropospheric O3is a positive radiative forcing—leads to warmingBad QualitiesOzone absorbs UV radiation: has essentially allowed life to flourish—UV radiation damages DNAO3makes OH: OH is the atmosphere’s scavenger. Without it, we’d be hurting. OH chews up CO, CH4, etc.Good QualitiesEffects of Human ActivitiesEffects of Human ActivitiesO3existed naturally before humans. But human emissions tend to increase tropospheric ozone and decrease stratospheric ozone (for different reasons)Decreased stratospheric O3increased UV exposure (bad)Increased surface and UT O3increased health problems (bad)increased greenhouse effect (bad)Ozone DamageOzone DamageNeedle damage (tip necrosis) is a common sign of ozone damage on pines.Often observed in forests downwind of major urban areas—Sierra Nevada, New England, Mexico City, etc.Ozone MeasurementsOzone Measurements——Important to Important to solving Osolving O33Hole PuzzleHole PuzzleDirect MethodsPull air into an instrument, measure:•Ozone absorption of UV light•Current or light made by chemical reaction with ozone.--balloons, ground, aircraftRemote MethodsUse UV radiation from sun or laser to quantify ozone in a column by its absorption while traveling through atmosphere.--ground, aircraft, satellitesOzone MeasurementsOzone Measurements——Important to Important to solving Osolving O33Hole PuzzleHole PuzzleGlobal Distribution of Total OzoneGlobal Distribution of Total Ozonemostly stratospheric ozoneMeasured in Dobson Units, •total amount of ozone above a location on Earth surface.Total O3varies strongly with latitudeResult of chemistry and stratospheric winds.How is OHow is O33Produced?Produced?In stratosphere: photolysis of O2makes O3OO33DestructionDestructionO3is naturally destroyed by trace nitrogen and hydrogen oxides. (O atoms are only a minor sink for O3)O3+ X  XO + O2XO + O  X + O2NET: O3+ O  2O2XXOO2O3catalytic destructionA catalyst is a reactant that increases rate of reaction without being consumed Small amount of a catalyst can have great influenceO2OCatalytic “O3Grinder”“X” can be NO, OH, Cl,…Important OImportant O33Destruction CatalystsDestruction CatalystsNO* (nitric oxide): comes from N2O (nitrous oxide) which is produced by bacteria in soils.OH* (hydroxyl radical): comes from water vaporCl (chlorine atoms): come from “organic halogen”compounds (small natural sources)All of these have natural sources, but human activity can increase NO and N2O (aircraft, fertilizer use) and Cl (CFCs).*NO and OH are most important, natural, O3destruction catalystsNitrogen oxide and Halogen SourcesNitrogen oxide and Halogen SourcesYearYearTypical Chlorofluorocarbon (CFC)N2O increasing as a result of fertilizer use“Montreal Protocol”Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs)Non-toxic, non-flammable, stable gases that are easily compressed.Used as refrigerants and as propellants in spray cansThought to be ideal…due to safety and durability.“Aerosol” Spray Cans: NOT SAME AS ATMOSPHERICAEROSOL PARTICLESEarly Warning SignsEarly Warning SignsMario Molina (a graduate student at the time!), Sherwood Roland, and Paul Crutzen—developed understanding of how O3is destroyed (naturally and by humans)NOBEL PRIZE1974: Molina and Rowland predict depletion by Chlorine from CFCs (but did not predict ozone hole!)Nature, June 28 1974Trend in ExtraTrend in Extra--Polar Stratospheric OPolar Stratospheric O33Change in Average Column Amount from 60S – 60NMt. PinatuboeruptionYellow Line: Prediction from chlorine chemistryRelative change ~ 2-3% lowerPolar Ozone LossPolar Ozone LossSevere depletion of stratospheric O3occurs every spring (since 1980’s) over the poles (especially South Pole).Example of: •the far reach of human activities•an environmental catastrophe and the political blame game•scientific process and ability of humans to correctDiscovery of Antarctic Ozone Discovery of Antarctic Ozone HoleHoleOzone HoleOzone Hole•Characterization of Ozone Hole•Finding the “Smoking Gun” With Human Fingerprints•Evolution of the ozone hole: putting the pieces together•The


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UW ATMS 211 - Stratospheric vs Tropospheric Ozone

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