職位詳細說明書銷售總監(jiān)

1、職位詳細說明書銷售總監(jiān)SpeciesNatural processesanthropogenicPresent burden vs pre-industrialElements of climate affecting emissionsPrimary particlesMineral dust Wind erosionLand use change, industrial dustIncr.Changing winds and precipitationSea saltWindChanging windsBiolog. Part.Wind, biolog. processesAgricult

2、ure?Changing windsCarb. Part.Vegetation firesFossil fuel & biomass burningIncr.Changing precip.SecondaryDMSPhytoplankton degradationMore sulfateChanging windsSO2Volc emissionsFossil fuel comb.More sulfateNH3Microbial activityAgricultureMore ammonium nitrateNOxLightningFossil fuel comb.Incr. nitrateC

3、hange in convective activityVOCVegetationIndustrial processesIncr. Org. aerosolAerosol propertiesGas emissions leading to secondary aerosolDimethylsulfide (DMS) SO2 emissions from volcanoesIndustrial SO2 emissionsNitrogen oxides and ammoniaVolatile Organic compounds (VOC)DMS, (CH3)2S, is the major o

4、ne of biogenic gases emitted from sea is produces during decomposition of dimethyl-sulfonpropionate (DMSP) from dying phytoplanktonmean residence time is about 1-2 days - most of S from DMS is also re-deposited in the ocean only small fraction lost into the atmosphereDimethylsulfideRecent global est

5、imates of DMS flux from the oceans range from 8 to 51 Tg S a-1This is 50% of total natural S-emissions (presently nearly equivalent to anthropogenic emissions, 76 Tg S a-1)- Differences in the transfer velocities in sea-to-air calculationsUncertainties are due to:- DMS seawater measurements (paucity

6、 of data in winter months and at high latitudes)DMS and ClimateDMS is emitted by phytoplankton as a natural biproduct of metabolismPossibly related to radiation protectionGives sea water its characteristic smellForms much of the natural aerosol (sub-micron particles) in oceanic airDMS is the major b

7、iogenic gas emitted from sea and the major source of S to the atmosphere. It contributes to the sulfur burden in both the MBL and FT.Figure adapted from Charlson et al. (1987) “Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate” Nature, vol. 326, pp. 655-661The CLAW Hypothesis(Char

8、lson, Lovelock, Andreae and Warren, 1987)DMS from the ocean affects cloud properties and can feedback to the plankton communityThis acts to regulate climate by increasing cloud albedo when sea-surface temperatures rise.DMS oxidationThe atmospheric oxidation pathways that lead from DMS to ionic speci

9、es (essentially sulfate and methanesulfonic acid, MSA, CH3SO3H) are complex and still poorly understood The first step to sulfate is SO2SO2 is largely dominant vs MSA, except at high latitudes (reasons unclear)MSA is unique for tracing marine biological activity, since it has no other sourceAbout at

10、mospheric SO2SO2 has several sources: either natural: marine MSA and volcanismor anthropogenic: mining and fossil fuel burningIts oxidation ways to SO4- are still matter to investigation, in particular with the aid of S & O stable isotopesThis can occur either in the gaseous phase by OH radicals or

11、in the liquid phase by O3 or H2O2 .Generally gaseous phase process is dominant, except in regions of high sea salt concentrations0%50%100%Percent (%) change in concentrations (yearly average)Case A: SO2/SO42- concentration without sea-salt chemistry Case B: With sea-salt chemistrySO2 (decrease)SO42-

12、 (small increase)Effect of sea-salt chemistry on SO2 and SO42- concentrations50%0%100%Effect of sea-salt chemistry on gas-phase sulfate production ratesMar/Apr/MayJun/Jul/AugSep/Oct/NovDec/Jan/FebPercent (%) decrease (seasonal average):Aqueous versus Gas Phase OxidationBiological regulation of the c

13、limate? (Charlson et al., 1987)DMSOHNO3SO2H2SO4OHNew particle formationCCNH2O2Light scatteringGas-phaseAqueous-phaseAqueous-phaseO3SO2 emissions from volcanoes (1)Volcanoes are a major natural source of atmospheric S-speciesInjections are generally occurring in the free troposphereMost active volcan

14、oes are in the Northern Hemisphere (80%)The strongest source region is the tropical belt, in particular IndonesiaEmissions are in the form of SO2, H2S and SO4- SO2 emissions from volcanoes (2)560 volcanoes over the world are potential SO2 sources, but only a few have been measuredVolcanic activity i

15、s sporadic, with a few cataclysmic eruptions per centuryCataclysmic eruptions inject ash particles and gases (mainly SO2) into the stratosphere, where H2SO4 formed forms a veil (Junge layer) Volcano locationsContinuously erupting volcanoesAtmospheric impact of volcanoesSO2 relatively insoluble, resi

16、sts tropospheric washoutInjected into the stratosphere in large quantities (Pinatubo, 1991 20 Tg)In stratosphere, SO2 oxidises to produce sulfuric acid aerosols (H2SO4)Conversion of SO2 to H2SO4 slow (months), aerosol cloud replenished months after eruptionThe total amount of volcanic tropospheric S

17、-emissions is presently estimated at: 14 +/- 6 Tg a-1 Mean volcanic sulfur emissions are of comparable importance for the atmospheric sulfate burden as anthropogenic sources because they affect the sulfate concentrations in the middle and upper troposphere whereas anthropogenic emissions control sul

18、fate in the boundary layer.S-isotope measurements in central polar regions (i.e. in the free troposphere) seem to support the important role of volcanic sulfur Acid aerosols reside in the stratosphere for several yearsAerosol veils increase optical depth of the atmosphere (inc. optical depth of 0.1%

19、 = 10% reduction sunlight reaching Earth surface). Spread around the globe by stratospheric winds Injection of acid aerosols into stratosphere is thefundamental process governing the atmospheric impact of volcanic eruptionsVolcanic aerosol and global atmospheric effectsAtmospheric effects of volcani

20、c eruptions1. Tropospheric cooling due to increased albedoEffects of aerosols can be direct or indirectAlbedo increased indirectly when aerosols fall out of the stratosphereNucleate clouds in troposphere - increase albedoRecent major volcanic eruptions produced significant cooling anomalies (0.4-0.7

21、oC) in the troposphere for periods of 1 to 3 yearsMagnitude of volcanic effects masked by natural variations (e.g. El Nino)2. Stratospheric warmingAcid aerosols absorb incoming solar radiation, heating the tropical stratosphere, e.g. Mt. Agung (1963), El Chichon (1982), and Pinatubo (1991) all cause

22、d warming of the lower stratosphere of 2oC3. Enhanced destruction of stratospheric ozoneEl ChichonPinatuboLower stratospheric temperature (global mean)Localised heating in the stratosphere can influence how far volcanic aerosol veils spread, by influencing stratospheric wind patterns+3oC-3oC0oCStrat

23、ospheric warmingVolcanoes do not inject chlorine into the stratosphere.Aerosols improve efficiency with which CFCs destroy ozone,by activating anthropogenic bromine and chlorine, indirectly leading to enhanced destruction of stratospheric ozoneRelatively short lived - aerosols last only 2-3 years in

24、 the stratosphereReduction in ozone following the June 1991 eruption of Pinatubo Enhanced destruction of stratospheric ozoneSeveral factors combine to determine whether a volcanic eruption has thepotential to influence the global atmosphere1. Eruption styleEnergetic enough to inject aerosols into th

25、e stratosphereLarger eruptions do not necessarily have greater effects Increased SO2 results in larger particles, not moreFall from the stratosphere faster, smaller optical depth per unit massvolcanic effects on the atmosphere may be self-limiting2. Magma chemistryImportance of acid aerosols means t

26、hat large eruptions of sulphur-poormagma less significant than sulfur-rich magmase.g. Mt St Helens - sulfur poor - negligible global effectsAtmospheric “effectiveness”3. LatitudeProximity to the stratosphere: smaller eruptions at high latitude can inject as much SO2 into the stratosphere as larger e

27、ruptions at lower latitudesStratospheric dispersal: Aerosols from tropical eruptions have the potential to spread around the globe (e.g Pinatubo). Atmospheric influence of eruption outside the tropics is contained within the middle and polar latitudes of the hemisphere of originAtmospheric“effective

28、ness”Atmospheric processes are complex !Understanding how an atmospheric perturbation influences climate and weather is still problematic, even for largest eruptionsHowever, understanding how volcanoes effect climate necessary to isolate other forcing processesComparison of chronology of known erupt

29、ions and climatic data shed light on the ways climate responds to large volcanic eruptions Volcanic eruptions and climate1. The written recordCompare eruption chronologies with written records of unusualclimatic eventse.g. Benjamin Franklin (1784) During several months of the summer of the year 1783

30、, when the effects of the Suns rays to heat the Earth should have been the greatest, there existed a constant fog over all of Europe, and great parts of North America. = 1783 - Laki fissure eruption, IcelandDisadvantages: record only a couple of thousand years, humans unreliable, eruption chronologi

31、es incomplete, geographical bias (e.g. no humans = no record)Making the connection2. Ice coresAcid aerosols fall on ice fieldsAccumulation of ice preserves information - acidity profileClimatically significant eruptions can be identified with great precisionAdvantages: objective, precise, records cl

32、imatically significant eruptions onlyDisadvantages: Which eruptions and why? Only those with high sulfur contents. Geographical bias. HALF of known large eruptions not recorded in Greenland ice coresMaking the connection3. Tree ringsProxy witnesses to eruptionsTemperate trees record passage of seaso

33、ns in growth rings - dendochronologyChanges in ring spacing, frost damage correlate with known eruptions Advantages: Trees, are old! Record extends back thousands of years. Objective, preciseDisadvantages: Tree growth sensitive to things apart from climate. Local environmental factors significantMak

34、ing the connection20 km3 of pyroclastic material in a Plinian column 40 km highAerosol veil circumnavigated the globe in 2 weeksInitially confined to the tropics, later spread to higher latitudes inboth hemispheresCaused spectacular sunsets worldwide 20% fall in radiant energy reaching Europe after

35、the eruptionAverage Northern Hemisphere cooling of 0.25oC, more pronounced athigher latitudes (-1oC)Case study: Krakatau, 188350 km3 of pyroclasts, Plinian column 43 km highAerosol veil reached London in about 3 monthsMany climatic effects attributed to Tambora1816 - the year without a summerinspire

36、d FrankensteinAnomalously cold winter in North America and EuropeWidespread crop failures, famineCase study: Tambora, 1815Global sulfur emissions GLOBAL SULFUR EMISSION TO THE ATMOSPHERE (1990 annual mean)Chin et al. 2000Industrial SO2 emissionsDuring the last decade, researchers from different coun

37、tries have prepared separate country-level inventories of anthropogenic emissions (GEIA= Global Emission Inventory Activity). In regions were local inventories were not available, estimates based on fossil fuel consumptions and population were calculated.In 1985: about 81% of anthropogenic sulfur em

38、issions were from fossil fuel combustion, 16 % from industrial processes, 3 % from large scale biomass burning and 1% from the combustion of biofuels, but these figures have to be revised for more recent years.The total amount for 1985 is estimated at :76 Tg S a-1, accurate to 20-30%Anthropogenic su

39、lfur emissionsFuture SO2 emissions in Asia are likely to be much lower than the latest IPCC forecastsSources of nitrogen oxidesand ammoniaAircraft0.5NOx: 32 TgN anthropogenic 11 TgN naturalFluxes in TgN/yearNitrogen oxidesThey are important in atmospheric oxidant chemistryThey are precursors for nit

40、ric acid which is a contributor to atmospheric acidity and reacts with NH3 and alkaline particlesGlobal NOx emissions (Tg/yr)A century of NOx emissions(van Aardenne et al., GBC, 15, 909, 2001)1890: dominated bytropical biomass burning1990: dominated bynorthern hemisphereindustrializationGlobal NOx f

41、rom lightningAmmonia NH3Ammonia is the primary basic (i.e. not acidic) gas in the atmosphere, and after N2 and N2O, the most abundant nitrogen containing gas in the atmosphereThe significant sources of NH3 are animal wastes, ammonification of humus, emissions from soils, loss of fertilizer from soils and industrial sources see next tableThe ammonium ion, NH4+ is an important component of continental tropospheric aerosols (as is NO3-) forming NH4NO3NH3 is highly water soluble and therefore has a residence time in the troposphere