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]