Update on CAM/CLM Biogenic VOC Emissions and Secondary Organic Aerosols

Chemistry-Climate Working Group Meeting, CCSMFebruary, 2007

Colette L. Heald(heald@atmos.berkeley.edu)

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

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)

BVOC EMISSIONS SCHEME

Flux = Emission Factor x Activity Factor ()

LIGHT TEMPERATURE LEAF AGESOIL

MOISTURE

ISOPRENE

MONTERPENES

[Guenther et al., 2006]

[Guenther et al., 1995]

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

ANNUAL AVERAGE ISOPRENE EMISSION ACTIVITY FACTORS: 2000

DISTRIBUTION OF BVOC EMISSIONS: 2000

Annual Totals:Isoprene = 558 TgC/yrMonoterpenes = 45 TgC/yr

ISOPRENE MONOTERPENES

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

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%

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.

•EXTRAS

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]

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]

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