Biogenic vocs
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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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Biogenic vocs

BIOGENIC VOCs


Topics for today

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?


Large supply of biogenic vocs unrecognized until the 1990s

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

LATEST INVENTORIES OF BIOGENIC vs. ANTHROPOGENIC VOCs

…notice difference in scale!

Millet et al. [2007]


Isoprene controlling air quality and climate

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 today1

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?


Global estimates of biogenic non methane voc emissions total 1250 tg yr 1

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


Biogenic vocs

WHICH BVOCs ARE IMPORTANT?

Christine Wiedinmyer, NCAR


Biogenic vocs many compounds and pathways

BIOGENIC VOCs: MANY COMPOUNDS AND PATHWAYS

R. Fall 1999


Biogenic vocs

PARTICULARLY “IMPORTANT” COMPOUNDS

Isoprene (C5H8)

Monoterpenes(C10H16)

Sesquiterpenes (C15H24)

MBO (2-methyl-3-buten-2-ol, C5H10O)


Topics for today2

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?


Biogenic vocs

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


Biogenic vocs

Leaf and Branch-Level Enclosure Studies


Biogenic vocs

Above Canopy Flux Studies


Biogenic vocs

Aircraft Studies


Biogenic vocs

Satellite Studies: GOME HCHO

2.5x1016

molecules

cm-2

2

1.5

1

South

Atlantic

Anomaly

(disregard)

detection

limit

0.5

0

-0.5


Topics for today3

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?


Biogenic vocs

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


Model of emissions of gases and aerosols from nature megan

Model of Emissions of Gases and Aerosols from Nature: MEGAN

[Guenther et al., ACP, 2006]


Model of emissions of gases and aerosols from nature megan1

Model of Emissions of Gases and Aerosols from Nature: MEGAN


Biogenic vocs

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


Vegeation types plant functional types

VEGEATION TYPES (PLANT FUNCTIONAL TYPES)

CLM landcover


Pft specific emission factors

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

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]


Activity factors meteorological and phenological variables controlling emission

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


Global distribution of isoprene emissions

GLOBAL DISTRIBUTION OF ISOPRENE EMISSIONS

Distinct seasonality due to vegetation cover and activity factors

Guenther et al., 2006


Topics for today4

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?


How well do we know emissions

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!


Biogenic vocs

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


A missing factor isoprene emission inhibition by co 2

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 today5

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?


How will bvoc emissions respond to a future 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

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]


Additional complication changing vegetation

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]


Other unknown factor disturbance

OTHER UNKNOWN FACTOR: DISTURBANCE

Wildfires

Pine Beetle Outbreak

Kurz et al., 2008

Running et al., 2008


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