Transcript CCWG_20080212_heald

Update on:
1. Secondary Organic Aerosol
2. Biogenic VOC emissions
Colette L. Heald
[email protected]
Chemistry Climate Working Group Meeting
February 12, 2008
MODELING FRAMEWORK
Community Land Model (CLM3)
Datasets: Lawrence and Chase [2007]
Feddema et al. [2007]
LAI (MODIS)
Plant Functional Types
Soil moisture
Vegetation Temperature
BVOC Algorithms
Vegetation
Meteorology [Guenther et al., 1995; 2006]
Monterpenes: GEIA
Isoprene: MEGAN
BVOC Emissions
Radiation
Precipitation
Community Atmospheric Model
(CAM3)
Anthropogenic
Emissions,
GHG concentrations,
SST
Chemistry
Transport
Radiation
SOA production
SECONDARY ORGANIC AEROSOL FORMATION
SOA parameterization [Chung and Seinfeld, 2002]
SOA
VOCi + OXIDANTj  ai,jP1i,j + ai,jP2i,j
Gi,j
Condensation of
low vapour pressure
ROGs on preexisting aerosol
Reactive Organic
Gases
OH
OH, O3, NO3
Isoprene Monoterpenes
Y~2-5%
Equilibrium (Komi,j)
 also f(POA)
Pi,j
Y~15%
Ai,j
Parameters (a’s K’s) from latest smog chamber
studies (Caltech)
OH
Aromatics
Y~25%
SOA: WHAT IS IN “MY VERSION” OF CAM-CHEM
•
•
•
•
2-product model SOA
3 classes of SOA (5 tracers):
– Monoterpenes (+OH, +O3, +NO3) [Chung and Seinfeld, 2002]
– Isoprene (+OH) [Henze and Seinfeld, 2006]
– Aromatics (Benzene, Toluene, Xylene + OH) [Henze et al., 2008]
• Yields are dynamically NOx dependent
Include temperature sensitive partitioning coefficients
Iteratively solves for gas-particle equilibrium at every time-step
(therefore carry gas phase SOA = SOG as tracers), allows for revolatilization
BOTTOM LINE: addition of SOA/SOG, and rudimentary oxidation
scheme for aromatics adds many tracers:
– 5 SOA, 5 SOG, Xylene/Benzene + oxidation products = 18
CAM-Chem now includes the state of the art for parameterized SOA modeling.
PROBLEM: This may not be enough!
DISCUSSION: Are simplifications possible to incorporate into Ghan aerosol
scheme? Is this desirable?
STATUS: BVOC EMISSIONS IN CLM3.5
Fluxes passed from CLM  CAM
MONOTERPENES:
ISOPRENE:
As in Levis et al. [2003]
Based on Guenther et al. [1995]
MEGAN v2 [Guenther et al., 2006]
(includes T, PAR, soil moisture, LAI, leaf age)
ANNUAL TOT: 43 TgC/yr
ANNUAL TOT: 495 TgC/yr
Note: To run with MEGAN2 need new fsurdat
file for CLM with isoprene basal emission rates
TO DO: Implement MEGAN2 emission factors for 19 other species
(monoterpenes, sesquiterpenes, other OVOCs, etc.). Associated changes
to chemical mechanism?
INHIBITION OF ISOPRENE EMISSION DUE TO CO2
Several plant growth studies show
that isoprene emission is inhibited in a
high-CO2 environment.
[Possell et al., 2005]
Mick Wilkinson and Russ Monson (UC Boulder) have examined isoprene
emission for 4 plant species as a function of both short-term and longterm CO2 exposure. They have parameterized the observed
relationships for one species (aspen) which can be added to the MEGAN
v2 activity factors [Wilkinson et al., in prep].
Some preliminary results when implemented in CLM…
FOR PRESENT-DAY (2000): EFFECT IS SMALL
Annual global total isoprene emissions increase by 7% (from 495 TgC/yr to
530 TgC/yr (mostly in Australia, Amazon)
FOR FUTURE (2100 A1B): CO2 INHIBITION
COMPENSATES FOR TEMPERATURE INCREASE
Future projected emissions drop
from 615 TgC/yr to 506 TgC/yr
(again, primarily in Australia and
the Amazon)
Dotted=2000
Solid=2100
See that ↑in T activity factor ~ compensated by ↓ in CO2 activity factor
CONCLUSION: ISOPRENE EMISSIONS
PREDICTED TO REMAIN ~CONSTANT
Important implications for oxidative environment of the troposphere…
[Heald et al., in prep]
MEGAN v2 COMPOUNDS
Compound/Class Name
Isoprene
MBO
Myrcene
Sabinene
limonene
carene <3->
ocimene <trans beta>
pinene <beta->
pinene <alpha->
farnescene <alpha->
caryophyllene <beta->
Methanol
Acetone
Acetaldehyde and ethanol
formic acid, formaldehyde,
acetic acid
methane
nitrogen gases: NO, NH3,
N2O
other monoterpenes
other sesquiterpenes
other VOC
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.15
0.15
0.09
0.11
0.13
Leaf
Age
Case
5
5
2
2
2
2
2
2
2
3
3
4
1
1
LDF
1
1
0.05
0.1
0.05
0.05
0.8
0.1
0.1
0.8
0.8
0
0
0
70
300
0.09
0.05
1
1
0
0.75
200
5
2
969
0.07
0.09
0.15
0.09
1
2
3
1
0
0.1
0.8
0.75
Class
ID
1
2
3
4
5
6
7
8
9
10
11
12
13
14
EFBT
map
5
20
45
45
18
90
90
180
60
60
400
100
120
EFNT
map
100
75
70
100
160
60
300
450
30
75
400
100
120
EFSHR
map
8
22
50
52
25
85
100
200
50
65
400
100
120
EFGC
map
0.1
0.3
0.7
0.7
0.3
1
1.5
2
0.9
1.2
400
100
120
15
16
70
300
70
300
70
300
17
18
19
20
5
87
108
969
5
180
125
969
41
108
104
969
b