Global linkages between vegetation atmospheric composition and climate
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Global Linkages Between Vegetation, Atmospheric Composition and Climate. Colette L. Heald Acknowledgements:

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Global linkages between vegetation atmospheric composition and climate

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


Global linkages between vegetation atmospheric composition and climate

+ 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


Future prediction of secondary organic aerosol

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]


Meteorological and phenological variables controlling isoprene emission

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]


Isoprene in the future

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 


Co 2 inhibition compensates for predicted temperature driven increase in isoprene emission

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)


Unless co 2 fertilization is strong

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]


Primary biological aerosol particles pbap

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?


Preliminary empirical pbap simulation

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)


Fungal pbap contributes 10 to fine mode oa source

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]


Challenges for understanding impact of vegetation on composition climate at the global scale

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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