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Black Carbon:Global Budget and Impacts on Climate

Black Carbon:Global Budget and Impacts on Climate. Soot Particle from a Wood-Burning Stove. Scanning electron microscope image of particles collected in Xianghe, W of Beijing. Structure of Soot. Outline. Soot: What is it? Climate Impact Physics Prior budgets INDOEX Budget evaluation

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Black Carbon:Global Budget and Impacts on Climate

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  1. Black Carbon:Global Budget and Impacts on Climate

  2. Soot Particle from a Wood-Burning Stove

  3. Scanning electron microscope image of particles collected in Xianghe, W of Beijing.

  4. Structure of Soot

  5. Outline • Soot: What is it? • Climate Impact • Physics • Prior budgets • INDOEX • Budget evaluation • Conclusions

  6. Climate forcing for atmospheric gases and aerosolsIPCC (2001) *Jacobson Nature, 2001.

  7. Radiation and fine particles

  8. Optical Properties & Visibility Change in intensity of light reflecting off an object I / I = exp(‑bextX) where: I = incident intensity of light I = change in intensity of light bext= extinction coefficient (m‑1) X = distance (m)

  9. Extinction Coefficient, bext Sum of scattering and absorption coefficients: bext = bscat + babs Decomposed further from gases and particles: babs = bag + bap bscat = bsg + bsp Where: bag= absorption coefficient due to gases (Beer's law) bap = absorption coefficient due to particles bsg = scattering coefficient due to gases (Rayleigh scattering) bsp = scattering coefficient due to particles (Mie scattering)

  10. Atmospheric Aerosols

  11. Optical Properties of Small Particles • = bscat/bext • = Single scattering albedo m = n + ik m = complex index of refraction n = scattering (real part) k = absorption (imaginary part)

  12. Refractive indicies of aerosol particles at  = 589 nm

  13. Radiative Effects (Climate Impact) of Soot • External mixture +0.27 Wm-2 • Coated core +0.54 Wm-2 • Well-mixed internally +0.78 Wm-2 (Jacobson, GRL., 2000)

  14. External vs. Internal Mixtures Sulfate & Soot mixed externally. Soot with sulfate coating (coated core). Well-mixed internally.

  15. Global Fossil Fuel Black Carbon Emissions(Cooke et al., JGR., 1999; Penner et al., 1993)

  16. Indian Today, 1996

  17. INDOEX, 1999 INDOEX Experimental Design

  18. NOAA R/V Ronald Brown

  19. Impactor Samples from Ship during INDOEX

  20. Origin of Soot? • Ratio of BC/OC near unity means origin should be fossil fuel • combustion (Novakov et al., 2001). • Low single scattering albedo, 0.81, indicates 70% from fossil • fuel combustion (Mayol-Bracero et al, 2001).

  21. Emissions InventoriesGg yr-1 Black Carbon from South AsiaHigh Estimate for 1999

  22. Estimate of BC Emissionfrom Ambient Measurements EBC = ECO*[BC]/[CO]/LBC Fort Meade, MD EBC = 90 Tg(CO)/yr * 0.0034 = 0.31 Tg(BC)/yr for N America (vs. 0.49 Tg(BC)/yr) INDOEX EBC = 87 Tg(CO)/yr * 0.0125/0.5 = 2.2 Tg(BC)/yr for South Asia (vs. 0.5 to 1Tg(BC)/yr)

  23. Two-Stroke Engine • No Valves • Oil mixed with gasoline • Part of fresh charged exhausted • Fuel adulteration

  24. Source Strength Black Carbon in China Estimated annual BC emissions from China: 1300-2600 Gg/yr Inventory: 1049 Gg/yr [Streets et al., 2003] Better agreement compared to a similar study for India [Dickerson et al., 2002] Single Scattering Albedo (SSA): Morning: ~0.81, Afternoon: ~0.85

  25. The ambient EC concentration decreases ~50% in the recent 11 years.

  26. The ambient OC concentration decreases ~10% in the recent 11 years.

  27. EC and OC are correlated (95-00) but show no obvious trend.

  28. EC shows a decreasing trend but no correlation with OC.

  29. At SHEN, EC decrease by ~15% in 8 years (1989-1997) while CO decrease by ~ 20% during the same period.

  30. Summary • Black Carbon (soot) may provide more forcing than methane. • Properties of aerosols suggest that fossil fuel combustion is main source of black carbon from South Asia. • Inventories suggest biofuels contribute substantially, and cannot support emissions above 1 Tg(BC) a-1. • Ambient measurements suggest major role for biomass burning and indicate 2-3 Tg(BC) a-1. • Combustion in S Asia is unlike anything seen in N America or Europe. • Time for direct measurements.

  31. Black Carbon References

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