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BIOGENIC VOCs

BIOGENIC VOCs. TOPICS FOR TODAY. Why do we care about BVOCs? How are they climate-relevant? What are BVOCs? Why are they emitted? How do we measure BVOC emissions? How do we model BVOC emissions? How well do we understand BVOC emissions?

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BIOGENIC VOCs

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  1. BIOGENIC VOCs

  2. TOPICS FOR TODAY • Why do we care about BVOCs? How are they climate-relevant? • What are BVOCs? Why are they emitted? • How do we measure BVOC emissions? • How do we model BVOC emissions? • How well do we understand BVOC emissions? • How might BVOC emissions respond to a changing climate?

  3. LARGE SUPPLY OF BIOGENIC VOCs – unrecognized until the 1990s Switches polluted areas in U.S. from NOx-saturated to NOx-limited regime! recognized in Revised Clean Air Act of 1999 Anthropogenic VOCs Isoprene (biogenic VOC) Jacob et al., [1993]

  4. LATEST INVENTORIES OF BIOGENIC vs. ANTHROPOGENIC VOCs …notice difference in scale! Millet et al. [2007]

  5. ISOPRENE: CONTROLLING AIR QUALITY AND CLIMATE C5 H8: Reactive hydrocarbon emitted from plants (primarily broadleaf trees) Annual global emissions ~ equivalent to methane emissions CLIMATE Depletes OH = ↑ CH4 lifetime + OH O3 AIR QUALITY Beijing IPCC, 2007

  6. TOPICS FOR TODAY • Why do we care about BVOCs? How are they climate-relevant? • What are BVOCs? Why are they emitted? • How do we measure BVOC emissions? • How do we model BVOC emissions? • How well do we understand BVOC emissions? • How might BVOC emissions respond to a changing climate?

  7. GLOBAL ESTIMATES OF BIOGENIC NON-METHANE VOC EMISSIONSTotal: ~1250 Tg yr-1 Other non- reactive VOCs 260 Tg Isoprene 600 Tg Other reactive VOCs 260 Tg Monoterpenes 130 Tg Guenther et al. 1995; Guenther et al. 2006

  8. WHICH BVOCs ARE IMPORTANT? Christine Wiedinmyer, NCAR

  9. BIOGENIC VOCs: MANY COMPOUNDS AND PATHWAYS R. Fall 1999

  10. PARTICULARLY “IMPORTANT” COMPOUNDS Isoprene (C5H8) Monoterpenes(C10H16) Sesquiterpenes (C15H24) MBO (2-methyl-3-buten-2-ol, C5H10O)

  11. TOPICS FOR TODAY • Why do we care about BVOCs? How are they climate-relevant? • What are BVOCs? Why are they emitted? • How do we measure BVOC emissions? • How do we model BVOC emissions? • How well do we understand BVOC emissions? • How might BVOC emissions respond to a changing climate?

  12. TOOLS FOR INVESTIGATING TRACE GAS FLUXES Analysis using ambient concentrations, isotopes and oxidation products Satellite data (e.g. HCHO) Regional Characterization Years Process studies Tower-based flux meas. systems Days Aircraft and blimp-based flux measurement systems Enclosure flux meas. systems TIME SCALE Hours Seconds Leaf Canopy Landscape Regional/global SPATIAL SCALE Christine Wiedinmyer, NCAR

  13. Leaf and Branch-Level Enclosure Studies

  14. Above Canopy Flux Studies

  15. Aircraft Studies

  16. Satellite Studies: GOME HCHO 2.5x1016 molecules cm-2 2 1.5 1 South Atlantic Anomaly (disregard) detection limit 0.5 0 -0.5

  17. TOPICS FOR TODAY • Why do we care about BVOCs? How are they climate-relevant? • What are BVOCs? Why are they emitted? • How do we measure BVOC emissions? • How do we model BVOC emissions? • How well do we understand BVOC emissions? • How might BVOC emissions respond to a changing climate?

  18. MODELING BIOGENIC EMISSIONS: MEGAN Model of Emissions of Gases and Aerosols from Nature Guenther et al., 2006 • Input files available at: http://cdp.ucar.edu

  19. Model of Emissions of Gases and Aerosols from Nature: MEGAN [Guenther et al., ACP, 2006]

  20. Model of Emissions of Gases and Aerosols from Nature: MEGAN

  21. HOW EMISSIONS ARE CALCULATED IN MEGAN F: Emission Flux (g m-2 hr-1) i: gridbox index j: vegetation type index : Emission Factor (g m-2 hr-1) at standard conditions for each vegetation type : fractional area coverage of vegetation type : Activity Factor (accounting for non-standard conditions) : production/loss within canopy factor Guenther et al., 2006

  22. VEGEATION TYPES (PLANT FUNCTIONAL TYPES) CLM landcover

  23. PFT-SPECIFIC EMISSION FACTORS On average, emission from broadleaf trees are 6x higher than needle evergreen, 20x higher than needle deciduous, and 2 orders of magnitude higher than crop emissions! Guenther et al., 2006

  24. BVOC EMISSIONS SCHEME Flux = Emission Factor x Activity Factor () SOIL MOISTURE LIGHT TEMPERATURE LEAF AGE ISOPRENE MONTERPENES [Guenther et al., 2006] [Guenther et al., 1995]

  25. ACTIVITY FACTORS: METEOROLOGICAL AND PHENOLOGICAL VARIABLES CONTROLLING EMISSION • LIGHT • Diffuse and direct radiation • Instantaneous and accumulated (24 hrs and 10 days) • TEMPERATURE (Leaf-level) • instantaneous and accumulated (24 hrs, 10 days) 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

  26. GLOBAL DISTRIBUTION OF ISOPRENE EMISSIONS Distinct seasonality due to vegetation cover and activity factors Guenther et al., 2006

  27. TOPICS FOR TODAY • Why do we care about BVOCs? How are they climate-relevant? • What are BVOCs? Why are they emitted? • How do we measure BVOC emissions? • How do we model BVOC emissions? • How well do we understand BVOC emissions? • How might BVOC emissions respond to a changing climate?

  28. HOW WELL DO WE KNOW EMISSIONS? • How well to we know the rates of compounds we can currently measure? • What chemical species don’t we see? • Controlling variables? • Long-term Controls • Chemical Environment • Effects of stress • Drought • Oxidants • Herbivory • … LOTS YET TO LEARN!

  29. SPRING 2006 TERPENOID EMISSIONS FROM A EUCALYPTUS FOREST NEAR TUMBARUMBA AUSTRALIA We are using the controlled environment of a growth chamber to investigate the processes controlling this behavior Snowstorm but not this Models can predict this A. Guenther

  30. A MISSING FACTOR: ISOPRENE EMISSION INHIBITION BY CO2 Long-Term growth environment: gene adaptation Dependent on ambient CO2 Short-term exposure: changes in metabolite pools and enzyme activity Dependent on intercellular CO2 Empirical parameterization from plant studies: [Wilkinson et al., GCB, in press] LESS Isoprene in a higher CO2 environment!

  31. TOPICS FOR TODAY • Why do we care about BVOCs? How are they climate-relevant? • What are BVOCs? Why are they emitted? • How do we measure BVOC emissions? • How do we model BVOC emissions? • How well do we understand BVOC emissions? • How might BVOC emissions respond to a changing climate?

  32. HOW WILL BVOC EMISSIONS RESPOND TO A FUTURE CLIMATE? NPP ↑ Temperature↑ 2000 2100 2000 2100-2000 Isoprene emissions projected to increase substantially due to warmer climate and increasing vegetation density. Some/all of this negated by increasing CO2 concentrations…? Heald et al. [2008]

  33. WHAT IS THE IMPACT OF THESE INCREASING EMISSIONS? 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]

  34. Greener biosphere? Shift in vegetation northwards? Changing plant species? ADDITIONAL COMPLICATION: CHANGING VEGETATION CLM DGVM projects a 3x increase in LAI and a northward expansion of vegetation. [Alo and Wang, 2008; Heald et al., in press]

  35. OTHER UNKNOWN FACTOR: DISTURBANCE Wildfires Pine Beetle Outbreak Kurz et al., 2008 Running et al., 2008

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