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BIOGENIC VOCs TOPICS FOR TODAY 1. Why do we care about BVOCs? How are they climaterelevant? 2. What are BVOCs? Why are they emitted? 3. How do we measure BVOC emissions? 4. How do we model BVOC emissions? 5. How well do we understand BVOC emissions? 6. How might BVOC emissions respond to a changing climate? 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] LATEST INVENTORIES OF BIOGENIC vs. ANTHROPOGENIC VOCs …notice difference in scale! Millet et al. [2007] 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 TOPICS FOR TODAY 1. Why do we care about BVOCs? How are they climaterelevant? 2. What are BVOCs? Why are they emitted? 3. How do we measure BVOC emissions? 4. How do we model BVOC emissions? 5. How well do we understand BVOC emissions? 6. How might BVOC emissions respond to a changing climate? GLOBAL ESTIMATES OF BIOGENIC NON-METHANE VOC EMISSIONS Total: ~1250 Tg yr-1 Other nonreactive VOCs 260 Tg Other reactive VOCs 260 Tg Isoprene 600 Tg Monoterpenes 130 Tg Guenther et al. 1995; Guenther et al. 2006 WHICH BVOCs ARE IMPORTANT? CLASS Major Emission Minor Emission Hemiterpenes isoprene, 2,3,2-MBO 2 compounds ? Monoterpenes a-pinene, b-pinene, carene, myrcene, sabinene, b-ocimene, limonene 30 compounds Many Sesquiterpenes caryophyllene, farnescence 30 compounds Many OxyVOC Methanol, acetone, acetaldehyde, ethanol 29 compounds ? Other VOC Methane, ethene, propene 21 compounds ? Unknowns ? ? ? Negligible Emission Christine Wiedinmyer, NCAR BIOGENIC VOCs: MANY COMPOUNDS AND PATHWAYS R. Fall 1999 PARTICULARLY “IMPORTANT” COMPOUNDS Isoprene (C5H8) Monoterpenes(C10H16) Sesquiterpenes (C15H24) MBO (2-methyl-3-buten-2-ol, C5H10O) TOPICS FOR TODAY 1. Why do we care about BVOCs? How are they climaterelevant? 2. What are BVOCs? Why are they emitted? 3. How do we measure BVOC emissions? 4. How do we model BVOC emissions? 5. How well do we understand BVOC emissions? 6. How might BVOC emissions respond to a changing climate? Years TOOLS FOR INVESTIGATING TRACE GAS FLUXES Regional Characterization Days Hours Tower-based flux meas. systems Aircraft and blimp-based flux measurement systems Enclosure flux meas. systems Seconds TIME SCALE Process studies Analysis using ambient concentrations, isotopes and oxidation products Satellite data (e.g. HCHO) Leaf Canopy Landscape Regional/global SPATIAL SCALE Christine Wiedinmyer, NCAR Leaf and Branch-Level Enclosure Studies Above Canopy Flux Studies Aircraft Studies Satellite Studies: GOME HCHO 2.5x1016 molecules cm-2 2 1.5 South Atlantic Anomaly (disregard) 1 0.5 detection limit 0 -0.5 TOPICS FOR TODAY 1. Why do we care about BVOCs? How are they climaterelevant? 2. What are BVOCs? Why are they emitted? 3. How do we measure BVOC emissions? 4. How do we model BVOC emissions? 5. How well do we understand BVOC emissions? 6. How might BVOC emissions respond to a changing climate? MODELING BIOGENIC EMISSIONS: MEGAN Model of Emissions of Gases and Aerosols from Nature Formic acid Methyl salicylate Ocimene Formaldehyde Octanal p-cymene Methanol Nonanal Piperitone Acetic acid a-phellandrene Sabinene Acetaldehyde a-pinene Terpineol Ethane a-terpinene Terpinolene Ethene a-thujene Dimethyl nonatriene Ethanol b-phellandrene Bornyl acetate Acetone b-pinene Methyl jasmonate Propene Camphene a-bergamotene Butene Camphor a-cedrene Butanone Cineole a-copaene Isoprene D-3-carene a-farnesene Methylbutenol Decanal a-humulene Hexanal D-limonene b-caryophyllene Hexenol g-terpinene b-farnesene Toluene Linalool Longifolene Hexenyl acetate Myrcene Input files available at: http://cdp.ucar.edu Guenther et al., 2006 Model of Emissions of Gases and Aerosols from Nature: MEGAN [Guenther et al., ACP, 2006] Model of Emissions of Gases and Aerosols from Nature: MEGAN HOW EMISSIONS ARE CALCULATED IN MEGAN Fi g i i , j j j 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 g: Activity Factor (accounting for non-standard conditions) : production/loss within canopy factor Guenther et al., 2006 VEGEATION TYPES (PLANT FUNCTIONAL TYPES) CLM landcover 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 BVOC EMISSIONS SCHEME Flux = Emission Factor x Activity Factor (g) LIGHT ISOPRENE [Guenther et al., 2006] MONTERPENES [Guenther et al., 1995] TEMPERATURE LEAF AGE SOIL MOISTURE 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) gT gL 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 GLOBAL DISTRIBUTION OF ISOPRENE EMISSIONS Distinct seasonality due to vegetation cover and activity factors Guenther et al., 2006 TOPICS FOR TODAY 1. Why do we care about BVOCs? How are they climaterelevant? 2. What are BVOCs? Why are they emitted? 3. How do we measure BVOC emissions? 4. How do we model BVOC emissions? 5. How well do we understand BVOC emissions? 6. How might BVOC emissions respond to a changing climate? 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! SPRING 2006 TERPENOID EMISSIONS FROM A EUCALYPTUS FOREST NEAR TUMBARUMBA AUSTRALIA 2 1.5 isoprene monoterpenes 1 Models can predict this Snowstorm Canopy Emission 2.5 We are using the controlled environment of a growth chamber to investigate the processes controlling this behavior but not this 0.5 0 313 314 315 316 317 318 Day of Year A. Guenther 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! TOPICS FOR TODAY 1. Why do we care about BVOCs? How are they climaterelevant? 2. What are BVOCs? Why are they emitted? 3. How do we measure BVOC emissions? 4. How do we model BVOC emissions? 5. How well do we understand BVOC emissions? 6. How might BVOC emissions respond to a changing climate? 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] WHAT IS THE IMPACT OF THESE INCREASING EMISSIONS? NPP ↑ Temperature↑ 2000 2100 Methane lifetime increases Surface O3 ↑ 10-30 ppb [Sanderson et al., 2003] [Shindell et al., 2007] SOA burden ↑ > 20% [Heald et al., 2008] ADDITIONAL COMPLICATION: CHANGING VEGETATION Greener biosphere? Shift in vegetation northwards? Changing plant species? CLM DGVM projects a 3x increase in LAI and a northward expansion of vegetation. [Alo and Wang, 2008; Heald et al., in press] OTHER UNKNOWN FACTOR: DISTURBANCE Wildfires Running et al., 2008 Pine Beetle Outbreak Kurz et al., 2008