update on cam/clm biogenic voc emissions and secondary organic aerosols
DESCRIPTION
Update on CAM/CLM Biogenic VOC Emissions and Secondary Organic Aerosols. Colette L. Heald ([email protected]). Chemistry-Climate Working Group Meeting, CCSM February, 2007. THE ROLE OF VOCs IN TROPOSPHERIC CHEMISTRY. h n. O 3. NO 2. NO. VOCs: contribute to O 3 formation - PowerPoint PPT PresentationTRANSCRIPT
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Update on CAM/CLM Biogenic VOC Emissions and Secondary Organic Aerosols
Chemistry-Climate Working Group Meeting, CCSMFebruary, 2007
Colette L. Heald([email protected])
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THE ROLE OF VOCs IN TROPOSPHERIC CHEMISTRY
NOx
VOC
OH HO2
CH4, CO, VOC
h
VOC
O3
ANTHROPOGENIC NATURAL
VOCs:1. contribute to O3
formation2. ↓OH ↑GHGs (eg. CH4)3. oxidation products can
form aerosols
NO2 NO
SOA
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PREVIOUS/STANDARD CAM (up to v3.3.41)• Includes Guenther [1995] emissions of monoterpenes and isoprene
within CLM Not passed to CAM chemistry simulation (BVOC are specified)
• No aromatic VOC emissions• SOA from monoterpenes only
UPDATES:• Implemented MEGAN [Guenther et al., 2006] emission scheme for
isoprene in CLM (monoterpene scheme the same at this time)Emissions passed to CAM
• Aromatic VOC emissions (RETRO) and oxidation reactions have been added for SOA scheme
• SOA scheme now includes isoprene and aromatics (benzene, toluene, xylene) according to latest yields from the Seinfeld group– Also fixed SOA scheme bug and added T-dependence for yields
Note: MEGAN being implemented in standard CAM by Francis Vitt, SOA is still research code (contact Colette Heald for more info)
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BVOC EMISSIONS SCHEME
Flux = Emission Factor x Activity Factor ()
LIGHT TEMPERATURE LEAF AGESOIL
MOISTURE
ISOPRENE
MONTERPENES
[Guenther et al., 2006]
[Guenther et al., 1995]
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PLANT FUNCTION TYPES (PFTs)CLM: 16 PFTs mapped to Guenther et al 6 PFTs
Isoprene basal emission factor for each PFT, each gridbox modulated by local conditions
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ANNUAL AVERAGE ISOPRENE EMISSION ACTIVITY FACTORS: 2000
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DISTRIBUTION OF BVOC EMISSIONS: 2000
Annual Totals:Isoprene = 558 TgC/yrMonoterpenes = 45 TgC/yr
ISOPRENE MONOTERPENES
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INTERACTIVE BVOC EMISSIONS SOA FORMATION
Community Land Model (CLM)
LAI (MODIS)Plant Functional Types
Soil moistureVegetation Temperature
BVOC Algorithms
Monterpenes: GEIAIsoprene: MEGAN
Community Atmospheric Model (CAM)
ChemistryTransportRadiation
BVOC Emissions
VegetationMeteorology
RadiationPrecipitation
SOA production
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SECONDARY ORGANIC AEROSOL FORMATION
Reactive Organic Gases
OH, O3, NO3
Monoterpenes AromaticsIsoprene
OHOH
SOA
Condensation of low vapour pressure
ROGs on pre-existing aerosol
SOA parameterization [Chung and Seinfeld, 2002]
VOCi + OXIDANTj i,jP1i,j + i,jP2i,j
Parameters (’s K’s) from latest smog chamber studies (Caltech)
Ai,j
GGi,ji,j
Pi,jPartition (Komi,j) also f(POA)
Also include temperature sensitivity:
Base case: ΔH = 42 kJ/mol (11-83)
, , , 2 , ,2
, , , 1 1 2 1
( ) 1 1exp
( )om i j k i j k
om i j k
K T HT
K T T R T T
Y~1-3% Y~5-15% Y~20-50%
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SURFACE SOA CONCENTRATIONS: 2000SOA (monoterpenes) SOA (isoprene) SOA (aromatics)
DJF
MAM
JJA
SON
TOTAL SOA PRODUCTION = 22 TgC
Global Burden:SOA (M): 0.05 TgCSOA (I): 0.40 TgCSOA (A): 0.10 TgCPOA: 0.88 TgC
Note: monoterpene emissions here are low compared to global estimates (~100 TgC/yr), may expect aromatic SOA to be comparable to monoterpene SOA.
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•EXTRAS
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ISOPRENE: LIGHT AND TEMPERATURE SCALING
24 240 240
1 1 1, ( , ), ( )
0.00831 opt optopt
x E f T T T f TT T
2 21P p
PC
P
1
2
2
2 1 1
T
T
C xT
T opt C xT T
C eE
C C e
LIGHTDiffuse and direct radiationInstantaneous and accumulated (24 hrs and 10 days)
TEMPERATURE (Leaf-level)instantaneous and accumulated (24 hrs, 10 days)
TPAR
LT
240 24 240( ), ( , )pf P C f P P
[Guenther et al., 2006]
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ISOPRENE: SOIL MOISTURE, PHENOLOGY, LAI
AMOUNT OF VEGETATION Leaf area index (LAI)
LEAF AGEMax emission = mature Zero emission = new
SOIL MOISTURE suppressed under drought
Month
LAISUMMER
[Guenther et al., 2006]
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MONTERPENES: TEMPERATURE, LAI
AMOUNT OF VEGETATION Leaf area index (LAI)
Month
LAISUMMER
[Guenther et al., 1995]
( )stdT TT e
TEMPERATURE (Leaf-level)Instantaneous only
NO LIGHT dependenceOutstanding: dependence on SOIL MOISTURE and LEAF AGE
T
T