sea-salt aerosol chemistry in geos-chem
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Becky Alexander
Rokjin Park, Daniel Jacob, Bob Yantosca1) Sea-salt emissions
2) Sea-salt/sulfate chemistry O-isotopes
3) New aerosol thermodynamics NO3-, NH4
+
4) DMS (concentrations, emissions, chemistry)
Sea-salt aerosol chemistry Sea-salt aerosol chemistry in GEOS-CHEMin GEOS-CHEM
GEOS-CHEM Sea-salt aerosol simulationGEOS-CHEM Sea-salt aerosol simulation
March 1998
January 1997
Na+ [g m-3]31 119750 13
dF/dr = 1.373u103.41r-3(1+0.057r1.05)101.19exp(-B2)
= (0.380 log r)/0.65
Monahan et al., 1986 (particles m-2 s-1 m-1)
2 size bins
(SALA & SALC)
fine: r = 0.1 – 0.5 m
coarse: r = 0.5 – 10 m
This can be easily changed (i.e. 2.5 m) in input.geos.
Details of sea-salt budget are in Alexander et al., 2005 (on web site)
GEOS-CHEM Sea-salt chemistryGEOS-CHEM Sea-salt chemistry
DMS
SO2
Free troposphere
H2SO4(g)
OH
Cloud other aerosols
(acid or neutral)
O3
CO2(g)
H 2O
2
Emission
Marine Boundary Layer
Subsidence
OH NO3
Sea-salt pH=8
HCO3-/CO3
2-
Emission
RCOOH(g)
HNO3(g)
Subsidence
Deposition
NH3(g)SO4
2-
Details of sea-salt chemistry are in Alexander et al., 2005 (on web site)
INDOEX CruisesINDOEX Cruises
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-15 -10 -5 0 5 10 15
nss
SO
42- D
17O
(‰
)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-15 -10 -5 0 5 10 15Latitude (degrees)
nss
SO
42- D
17O
(‰
)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-15 -10 -5 0 5 10 15
ns
sSO
42
- D1
7 O (
‰)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-15 -10 -5 0 5 10 15Latitude (degrees)
nssS
O42
- D17 O
(‰
)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-15 -10 -5 0 5 10 15Latitude (degrees)
ns
sSO
42- D
17 O
(‰
)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-15 -10 -5 0 5 10 15
ns
sSO
42- D
17 O
(‰
)
January 1997
March 1998
Extra sulfate tracers
Isotope version:
Primary SO42- D17O=0‰
SO2 + OH D17O=0‰
S(IV) + H2O2 D17O=0.9‰
S(IV) + O3 D17O=8.8‰
(in-cloud, SALA, SALC)
Standard version:
SO4S (sulfate formed in coarse sea-salt aerosols from S(IV) + O3)
SO4 (all other sulfate)
[SO2] % decrease
[SO42-] % increase
SO2 + OH % decrease
10 30 50 705
GEOS-CHEM Sulfur BudgetGEOS-CHEM Sulfur Budget
Aerosol ThermodynamicsAerosol Thermodynamics
RPMARES ISOROPIA
NO3-NH4
+
NH3 HNO3
HSO4-, SO4
2-
NO3-NH4
+
HNO3
HSO4-, SO4
2-
Cl-Na+
NH3
HCl
Nenes et al., 1998Saxena et al., 1986; Kim et al., 1993
SO4-NO3-NH4-H2O SO4-NO3-NH4-Na-Cl-H2O
Effects of Sea-salt chemistry and Effects of Sea-salt chemistry and ISOROPIA on HNOISOROPIA on HNO33 and NO and NO33
--
0 4 ppbv-4
HNO3
Absolute Difference
% Difference
0
100 %-100
NO3-
0
Effects of Sea-salt chemistry and Effects of Sea-salt chemistry and ISOROPIA on NHISOROPIA on NH33 and NH and NH44
0 7 ppbv-7
NH4+
Absolute Difference
% Difference
0
100 %-100
NH3
0
Future Model Development Plans: DMSFuture Model Development Plans: DMS
Seawater DMS concentrationsOld: Kettle et al. [1999]
New: Simó and Dachs [2002]
DMS sea-air transfer function
DMS Chemistry (DMS+BrO)
Boucher et al. [2003]
60
30
5
%
DMS oxidation
rate
0
20
40
60
80
100
120
140
160
180
200
0 5 10 15 2010m wind speed [m/s]
k DM
S [
cm/h
r]
Wanninkhov&McGillis [1999]
Wanninkhov et al. [1992]
Nightingale et al. [2000]
Liss&Merlivat [1986]
DMS = f(Chl/MLD)
0 2 4 6 8 10 12 14 16
DMS concentration (nM)
180 360 540 720
60
120
180
240
300
360
90 N
60 N
30 N
0
30 S
60 S
90 S
June
SeaWiFS
Extra slides
fSO2
fHNO3
fexcess
0.1 0.3 0.5 0.7
GEOS-CHEM Alkalinity BudgetGEOS-CHEM Alkalinity Budget
Latitude (°N)n
ssS
O4
2- D
17O
(‰
)
ObservationsModel with excess alkalinity
Sensitivity simulation: Excess alkalinitySensitivity simulation: Excess alkalinity
Na+, Cl-
OH(g) + Cl-(interface) (HO…Cl-)interface
(HO…Cl-)interface + (HO…Cl-)interface Cl2 + 2OH-
2OH-
Cl2
2OH•
Laskin et al., 2003
Transfer rate constant [Schwartz, 1986]
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