Aerosols Why are we interested in them?

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1 Aerosols Why are we interested in them? Health problems Decrease visibility Reduce (normally) the amount of solar radiation that reach the ground Affects surface energy balance Plant growth Provide cloud condensation nuclei Provide surface area for heterogeneous chemical reactions

2 OZONE AND PARTICULATE MATTER (PM): THE TOP TWO AIR POLLUTANTS IN THE U.S. # millions of people living in areas exceeding national ambient air quality standards (NAAQS) in ppb (8-h average) 15 mg m -3 (day), 65 (annual) 65 mg m -3 (24-h), 15 (annual)

3 The famous T-shirt figure

4 Potential impact of BC reductions (UNEP, 2011)

5 A general view of the CCTV towers, headquarters of China Central Television, in Beijing on January 12, 2013 Illustrasjon av redusert siktbarhet. Elektronisk manipulert. rg/topics/sustainability/w hat-would-your-city-lookbeijings-air-smogsimulator

6 Shenyang, November 2015

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8 VISIBILITY IN U.S. WILDERNESS AREAS 2001 observations Natural Background; includes transboundary pollution Deciviews Visual range (km) Park et al. [2006]

9 Høy relativ fuktighet i luften i grenselaget gjør at partiklene sveller mer spredning av lys.

10 The aerosol lifecycle Dråpevekst Köhler teori

11 Composition of aerosols Fine Mode (d < 1.0 μm) Sulphate Organics (Primary and secondary) Nitrate Ammonium Black carbon Coarse mode (d > 1.0 μm) Sea salt Mineral dust Biological material Fly ash

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13 WORLDWIDE MEASUREMENTS OF FINE AEROSOL COMPOSITION

14 Forurenset byluft Kontinental bakgrunn Marin bakgrunn Aerosol surface area distribution Principle sources for aerosols

15 1 um 1 nm

16 Kulmala et al, 2013.

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18 Små og store partikler blir lettere tatt opp av dråper Partikler med diameter rundt 0.1 um (accumulation mode) blir tatt opp minst effektivt

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22 Effekter på kortbølget stråling - Sikt - Strålingspådriv (klima)

23 Strålingspådriv (radiative forcing)

24 Strålingspådriv (radiative forcing)

25 Direkte, semi-direkte og indirekte effekter av aerosoler

26 Strålingspådriv pga. direkte effekten av spredende aerosoler (sulfat, nitrat, organisk karbon, mineralstøv). Finner da ΔF=-0.9 Wm -2

27 IPCC, 2013

28 Indirekte effekter av aerosoler på skyer

29 IPCC,2013

30 Remaining fraction (%) Hvordan sammenlikne klimaeffekten av et utslipp av 2 ulike komponenter? Forskjellene i tidsskalaene er hovedutfordringen når vi skal sammenlikne effektene 100 % 80 % 60 % 40 % 20 % CO2 CH4 SF6 N2O HFC-134a CF4 0 % Years

31 IPCC (1990, 1992, 1996) ++ Global Warming Potential (GWP) IPCC, 2007

32 GTP en alternativ metric som bruker ΔT ved tiden H, jfr. 2º mål

33 AOD (Aerosol Optical Depth) Fra Myhre et al., ACP, AOD (δ): F t =F s e -δ Ulike observasjonsbaserte estimater spriker Modellene avviker omtrent like mye som forskjellen mellom observasjonene

34 Total aerosol forcing er lavere, pga. skyer og absorberende partikler Myhre, Science, 2009

35 ANNUAL MEAN PM 2.5 CONCENTRATIONS (2002) derived from MODIS satellite instrument data

36 GLOBAL SULFUR BUDGET [Chin et al., 1996] (flux terms in Tg S yr -1 ) cloud 42 SO SO 2 t = 1.3d OH 8 H 2 SO 4 (g) t = 3.9d NO 3 OH (CH 3 ) 2 S (DMS) t = 1.0d dep 27 dry 20 wet dep 6 dry 44 wet 22 Phytoplankton Volcanoes Combustion Smelters

37 U.S. SO 2 EMISSIONS Main source is coal combustion GLOBAL Industrial UNITED STATES Sulfur emissions, Tg a -1 Volcanoes Biomass burning Oceans

38 FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS HO 2 2 H SO ( g) SO 2H HO 2 NH ( g) NH OH 3 4 HO 2 HNO ( g) NO H 3 3 NH ( g) HNO ( g) NH NO ( aerosol) Thermodynamic rules: Sulfate always forms an aqueous aerosol Ammonia dissolves in the sulfate aerosol totally or until titration of acidity, whichever happens first Nitrate is taken up by aerosol if (and only if) excess NH 3 is available after sulfate titration HNO 3 and excess NH 3 can also form a solid aerosol if RH is low Condition aerosol ph Low RH High RH [S(VI)] > 2[N(-III)] acid H 2 SO 4 nh 2 O, NH 4 HSO 4, (NH 4 ) 2 SO 4 [S(VI)] 2[N(-III)] neutral (NH 4 ) 2 SO 4, NH 4 NO 3 (NH 4 +, H +, SO 4 2- ) solution (NH 4 +,NO 3 - ) solution

39 FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS HO 2 2 H SO ( g) SO 2H HO 2 NH ( g) NH OH 3 4 HO 2 HNO ( g) NO H 3 3 NH ( g) HNO ( g) NH NO ( aerosol) Thermodynamic rules: Sulfate always forms an aqueous aerosol Ammonia dissolves in the sulfate aerosol totally or until titration of acidity, whichever happens first Nitrate is taken up by aerosol if (and only if) excess NH 3 is available after sulfate titration HNO 3 and excess NH 3 can also form a solid aerosol if RH is low Condition aerosol ph Low RH High RH [S(VI)] > 2[N(-III)] acid H 2 SO 4 nh 2 O, NH 4 HSO 4, (NH 4 ) 2 SO 4 [S(VI)] 2[N(-III)] neutral (NH 4 ) 2 SO 4, NH 4 NO 3 (NH 4 +, H +, SO 4 2- ) solution (NH 4 +,NO 3 - ) solution

40 FORMATION OF SULFATE-NITRATE-AMMONIUM AEROSOLS HO 2 2 H SO ( g) SO 2H HO 2 NH ( g) NH OH 3 4 HO 2 HNO ( g) NO H 3 3 NH ( g) HNO ( g) NH NO ( aerosol) Thermodynamic rules: Sulfate always forms an aqueous aerosol Ammonia dissolves in the sulfate aerosol totally or until titration of acidity, whichever happens first Nitrate is taken up by aerosol if (and only if) excess NH 3 is available after sulfate titration HNO 3 and excess NH 3 can also form a solid aerosol if RH is low Condition aerosol ph Low RH High RH [S(VI)] > 2[N(-III)] acid H 2 SO 4 nh 2 O, NH 4 HSO 4, (NH 4 ) 2 SO 4 [S(VI)] 2[N(-III)] neutral (NH 4 ) 2 SO 4, NH 4 NO 3 (NH 4 +, H +, SO 4 2- ) solution (NH 4 +,NO 3 - ) solution

41 AMMONIA EMISSIONS Ammonia, Tg N a -1 GLOBAL Livestock Fertilizer Humans Industry Biofuels Soils/vegetation UNITED STATES Oceans 55 Biomass burning 2.8

42 What is black carbon aerosols? Product of incomplete combution Fossil fuels or biomass

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44 Bond et al., JGR, 2012

45 ng/g Annual BC concentration in snow Ice-core location D4 Greenland McConnell et al. (Science, 2007) 6 5 BC concentration in snow 1 st Aug ICEC-D4 FFC BIO

46 Geoengineering. En mulighet er å øke albedoen ved å øke aerosolmengden. SRM: Solar radiation management kan nøytralisere globalt midlet temperaturøkning, men ser ut til å redusere nedbør. Katharine L. Ricke, M. Granger Morgan & Myles R. Allen Nature Geoscience 3, (2010)

47 WILDFIRES: A GROWING AEROSOL SOURCE S. California fire plumes, Oct Total carbonaceous (TC) aerosol averaged over U.S. IMPROVE sites Interannual variability is driven by wildfires