BIOGENIC VOCs

TOPICS FOR TODAY 1.Why do we care about BVOCs? How are they climate- relevant? 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 Isoprene (biogenic VOC)Anthropogenic VOCs Jacob et al., [1993] Switches polluted areas in U.S. from NO x -saturated to NO x -limited regime! recognized in Revised Clean Air Act of 1999

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

ISOPRENE: CONTROLLING AIR QUALITY AND CLIMATE C 5 H 8 : Reactive hydrocarbon emitted from plants (primarily broadleaf trees) Annual global emissions ~ equivalent to methane emissions + OH O3O3 Depletes OH = ↑ CH 4 lifetime IPCC, 2007 Beijing CLIMATE AIR QUALITY

TOPICS FOR TODAY 1.Why do we care about BVOCs? How are they climate- relevant? 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?

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

WHICH BVOCs ARE IMPORTANT? CLASSMajor EmissionMinor Emission Negligible Emission Hemiterpenesisoprene, 2,3,2-MBO2 compounds? Monoterpenesa-pinene, b-pinene, carene, myrcene, sabinene, b-ocimene, limonene 30 compounds Many Sesquiterpenescaryophyllene, farnescence 30 compounds Many OxyVOCMethanol, acetone, acetaldehyde, ethanol 29 compounds ? Other VOCMethane, ethene, propene21 compounds ? Unknowns??? Christine Wiedinmyer, NCAR

BIOGENIC VOCs: MANY COMPOUNDS AND PATHWAYS R. Fall 1999

Isoprene (C 5 H 8 ) Monoterpenes(C 10 H 16 ) Sesquiterpenes (C 15 H 24 ) PARTICULARLY “IMPORTANT” COMPOUNDS MBO ( 2-methyl-3-buten-2-ol, C 5 H 10 O)

TOPICS FOR TODAY 1.Why do we care about BVOCs? How are they climate- relevant? 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?

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

Leaf and Branch-Level Enclosure Studies

Above Canopy Flux Studies

Aircraft Studies

x10 16 molecules cm -2 South Atlantic Anomaly (disregard) detection limit Satellite Studies: GOME HCHO

TOPICS FOR TODAY 1.Why do we care about BVOCs? How are they climate- relevant? 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?

Formic acidMethyl salicylateOcimene FormaldehydeOctanalp-cymene MethanolNonanalPiperitone Acetic acid  -phellandrene Sabinene Acetaldehyde  -pinene Terpineol Ethane  -terpinene Terpinolene Ethene  -thujene Dimethyl nonatriene Ethanol  -phellandrene Bornyl acetate Acetone  -pinene Methyl jasmonate PropeneCamphene  -bergamotene ButeneCamphor  -cedrene ButanoneCineole  -copaene Isoprene  -3-carene  -farnesene MethylbutenolDecanal  -humulene Hexanal  -limonene  -caryophyllene Hexenol  -terpinene  -farnesene TolueneLinaloolLongifolene Hexenyl acetateMyrcene MODELING BIOGENIC EMISSIONS: MEGAN Model of Emissions of Gases and Aerosols from Nature Guenther et al., 2006 Input files available at:

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

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 HOW EMISSIONS ARE CALCULATED IN MEGAN 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 (  ) LIGHTTEMPERATURELEAF AGE SOIL MOISTURE ISOPRENE MONTERPENES [Guenther et al., 2006] [Guenther et al., 1995]

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 PAR LL TT SOIL MOISTURE  suppressed under drought AMOUNT OF VEGETATION  Leaf area index (LAI) Month LAI SUMMER LEAF AGE  Max emission = mature  Zero emission = new 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 climate- relevant? 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 Snowstorm We are using the controlled environment of a growth chamber to investigate the processes controlling this behavior Models can predict this but not this A. Guenther

A MISSING FACTOR: ISOPRENE EMISSION INHIBITION BY CO 2 Long-Term growth environment: gene adaptation Dependent on ambient CO 2 Short-term exposure: changes in metabolite pools and enzyme activity Dependent on intercellular CO 2 Empirical parameterization from plant studies: [Wilkinson et al., GCB, in press] LESS Isoprene in a higher CO 2 environment!

TOPICS FOR TODAY 1.Why do we care about BVOCs? How are they climate- relevant? 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? Isoprene emissions projected to increase substantially due to warmer climate and increasing vegetation density. Some/all of this negated by increasing CO 2 concentrations…? NPP ↑ Temperature↑ Heald et al. [2008]

WHAT IS THE IMPACT OF THESE INCREASING EMISSIONS? NPP ↑ Temperature↑ Surface O 3 ↑ ppb [Sanderson et al., 2003] Methane lifetime increases [Shindell et al., 2007] SOA burden ↑ > 20% [Heald et al., 2008]

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] Greener biosphere? Shift in vegetation northwards? Changing plant species?

OTHER UNKNOWN FACTOR: DISTURBANCE Pine Beetle OutbreakWildfires Running et al., 2008 Kurz et al., 2008