Download How well do we understand BVOC emissions?

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