1. Becky Alexander Rokjin Park, Daniel Jacob, Bob Yantosca 1) Sea-salt emissions 2) Sea-salt/sulfate chemistry  O-isotopes 3) New aerosol thermodynamics  NO 3 -, NH 4 + 4) DMS (concentrations, emissions, chemistry) Sea-salt aerosol chemistry in GEOS-CHEM

2. GEOS-CHEM Sea-salt aerosol simulation March 1998 January 1997 Na + [  g m -3 ] 31 11975 0 13 dF/dr = 1.373u 10 3.41 r -3 (1+0.057r 1.05 )10 1.19 exp(-B 2 )  = (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)

3. GEOS-CHEM Sea-salt chemistry DMS SO 2 Free troposphere H 2 SO 4 (g) OH Cloud other aerosols (acid or neutral) O3O3 CO 2 (g) H2O2H2O2 Emission Marine Boundary Layer Subsidence OH NO 3 Sea-salt pH=8 HCO 3 - /CO 3 2- Emission RCOOH(g) HNO 3 (g) Subsidence Deposition NH 3 (g) SO 4 2- Details of sea-salt chemistry are in Alexander et al., 2005 (on web site)

4. INDOEX Cruises January 1997 March 1998 Extra sulfate tracers Isotope version: Primary SO 4 2-  17 O=0‰ SO 2 + OH  17 O=0‰ S(IV) + H 2 O 2  17 O=0.9‰ S(IV) + O 3  17 O=8.8‰ (in-cloud, SALA, SALC) Standard version: SO4S (sulfate formed in coarse sea-salt aerosols from S(IV) + O 3 ) SO4 (all other sulfate)

5. [SO 2 ] % decrease [SO 4 2- ] % increase SO 2 + OH % decrease 10305070 5 GEOS-CHEM Sulfur Budget

6. Aerosol Thermodynamics RPMARESISOROPIA NO 3 - NH 4 + NH 3 HNO 3 HSO 4 -, SO 4 2- NO 3 - NH 4 + HNO 3 HSO 4 -, SO 4 2- Cl - Na + NH 3 HCl Nenes et al., 1998Saxena et al., 1986; Kim et al., 1993 SO 4 -NO 3 -NH 4 -H 2 OSO 4 -NO 3 -NH 4 -Na-Cl-H 2 O

7. Effects of Sea-salt chemistry and ISOROPIA on HNO 3 and NO 3 - 04 ppbv-4 HNO 3 Absolute Difference % Difference 0 100 % -100 NO 3 - 0

8. Effects of Sea-salt chemistry and ISOROPIA on NH 3 and NH 4 07 ppbv-7 NH 4 + Absolute Difference % Difference 0 100 % -100 NH 3 0

9. Future Model Development Plans: DMS Seawater DMS concentrations Old: 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 Wanninkhov&McGillis [1999] Wanninkhov et al. [1992] Nightingale et al. [2000] Liss&Merlivat [1986] DMS = f(Chl/MLD) 0246810121416 DMS concentration (nM) 90 N 60 N 30 N 0 30 S 60 S 90 S June SeaWiFS

10. Extra slides

11. f SO2 f HNO3 f excess 0.10.30.50.7 GEOS-CHEM Alkalinity Budget

12. Latitude (°N) nssSO 4 2-  17 O (‰) Observations Model with excess alkalinity Sensitivity simulation: Excess alkalinity Na +, Cl - OH (g) + Cl - (interface)  (HO…Cl - ) interface (HO…Cl - ) interface + (HO…Cl - ) interface  Cl 2 + 2OH - 2OH - Cl 2 2OH Laskin et al., 2003

13. Transfer rate constant [Schwartz, 1986]