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Global Linkages Between Vegetation, Atmospheric Composition and Climate

Global Linkages Between Vegetation, Atmospheric Composition and Climate. Colette L. Heald Acknowledgements:

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Global Linkages Between Vegetation, Atmospheric Composition and Climate

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  1. Global Linkages Between Vegetation, Atmospheric Composition and Climate Colette L. Heald Acknowledgements: Dominick Spracklen,Russ Monson, Mick Wilkinson, Clement Alo, Guiling Wang, Alex Guenther, Daven Henze, Larry Horowitz, Johannes Feddema, Jean-Francois Lamarque, Peter Hess, Francis Vitt, John Seinfeld, Allen Goldstein, Inez Fung Fall AGU Meeting, San Francisco December 19, 2008

  2. + FEEDBACKS FROM CLIMATE CHANGE (moisture, precipitation, T, hv) ? SOA + oxidants ↓ OH = ↑ CH4 lifetime PBAP EMISSIONS: Particles Organics NOx … C5H8 O3 + oxidation DISTURBANCE: Fires, beetles, land use change ANTHROPOGENIC INFLUENCE

  3. FUTURE PREDICTION OF SECONDARY ORGANIC AEROSOL Sources may be large(?), how MIGHT they change? ZONAL MEAN SOA CONCENTRATIONS: 2100-2000 Global Model: NCAR CAM3-CLM3 (2x2.5) • (ANTHROPOGENIC EMISSIONS):POA (partitioning) • Aromatics (precursor) • Trace gases (NOx, oxidants) • (BIOGENIC EMISSIONS): • BVOC (precursor) • (CLIMATE): • Precipitation (lifetime) • T (partitioning, oxidation) • Convection (distribution, lifetime) • Lightning (NOx aloft) • Water vapour (POH)  (ANTHROPOGENIC LAND USE) Climate impact is complex/compensatory/uncertain. Predict large increase in SOA burden (> 20%) tied to T-driven BVOC emissions, with large sensitivity to future land use. [Heald et al., 2008]

  4. METEOROLOGICAL AND PHENOLOGICAL VARIABLES CONTROLLING ISOPRENE EMISSION • LIGHT • Diffuse and direct radiation • Instantaneous and accumulated (24 hrs and 10 days) • TEMPERATURE (Leaf-level) • instantaneous and accumulated (24 hrs, 10 days) Eisoprene≈ ECH4 T L T PAR AMOUNT OF VEGETATION  Leaf area index (LAI) • LEAF AGE • Max emission = mature • Zero emission = new LAI SUMMER Month SOIL MOISTURE  suppressed under drought [Guenther et al., 2006]

  5. ISOPRENE IN THE FUTURE NPP ↑ Temperature↑ 2000 2100 Methane lifetime increases [Shindell et al., 2007] SOA burden ↑ > 20% [Heald et al., 2008] Surface O3 ↑ 10-30 ppb [Sanderson et al., 2003] Isoprene emissions projected to increase substantially due to warmer climate and increasing vegetation density.  LARGE impact on oxidant chemistry and climate 

  6. CO2 INHIBITION COMPENSATES FOR PREDICTED TEMPERATURE-DRIVEN INCREASE IN ISOPRENE EMISSION Empirical parameterization from plant studies [Wilkinson et al., GCB, in press] MEGAN MEGAN with CO2 inhibition 696 Eisop (TgCyr-1) 523 508 479 2000 2100 (A1B) * With fixed vegetation CONCLUSION: Isoprene emission predicted to remain ~constant Important implications for oxidative environment of the troposphere… Global Model: NCAR CAM3-CLM3 (2x2.5)

  7. UNLESS…CO2 FERTILIZATION IS STRONG • CLM DGVM projects a 3x increase in LAI associated with NPP and a northward expansion of vegetation. • [Alo and Wang, 2008] • Isoprene emissions more than double! (1242 TgCyr-1) • BUT, recent work suggests that NPP increases may be overestimated by 74% when neglecting the role of nutrient limitation • [Thornton et al., 2007] [Heald et al., GCB, in press]

  8. PRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP) ALGAE VIRUSES BACTERIA POLLEN FUNGUS LARGE particles (> 10 µm) PLANT DEBRIS Jaenicke [2005] suggests may be as large a source as dust/sea salt (1000s Tg/yr) Elbert et al. [2007] suggest emission of fungal spores ~ 50 Tg/yr How much does this source contribute to fine-mode OC?

  9. PRELIMINARY EMPIRICAL PBAP SIMULATION Elbert et al. [2007] identify that mannitol is a tracer for fungal spores 1 pg mannitol = 39 pg OM* Emission = constant [Elbert al., 2007] Emission = f(LAI, H2O) PBAP OA (PM2.5) PBAP OA (PM2.5) Test a series of meteorological drivers for mannitol emission. BEST MATCH A number of meteorological drivers could be expected to modulate fungal PBAP emissions. Here we find LAI and atmospheric water vapour concentrations are the best predictors for observed average mannitol concentrations. Global Model: GEOS-Chem (2x2.5)

  10. FUNGAL PBAP CONTRIBUTES <10% TO FINE-MODE OA SOURCE Global Model: GEOS-Chem (2x2.5) Annual Mean Surface Concentrations Global Annual Emissions: 2003 66 Tg 30 21 7 POA SOA PBAP fine PBAP coarse 2.5-10 m < 2.5 m Consistent with AMS observations from AMAZE where OA concentrations were low. Need more PBAP observations! [Heald and Spracklen, in prep]

  11. CHALLENGES FOR UNDERSTANDING IMPACT OF VEGETATION ON COMPOSITION & CLIMATE AT THE GLOBAL SCALE HOW MUCH IS THERE??? • Land Use (Present/Future) • Species Diversity • Connecting scales: SCALE UP?

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