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Sea-salt aerosol chemistry in GEOS-CHEM

Sea-salt aerosol chemistry in GEOS-CHEM. 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). January 1997. March 1998.

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Sea-salt aerosol chemistry in GEOS-CHEM

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  1. Sea-salt aerosol chemistry in GEOS-CHEM Becky Alexander Rokjin Park, Daniel Jacob, Bob Yantosca 1) Sea-salt emissions 2) Sea-salt/sulfate chemistry  O-isotopes 3) New aerosol thermodynamics  NO3-, NH4+ 4) DMS (concentrations, emissions, chemistry)

  2. January 1997 March 1998 Na+ [mg m-3] 0 1 3 5 7 9 11 13 GEOS-CHEM Sea-salt aerosol simulation • dF/dr = 1.373u103.41r-3(1+0.057r1.05)101.19exp(-B2) • = (0.380 log r)/0.65 Monahanet al., 1986 (particles m-2 s-1mm-1) 2 size bins (SALA & SALC) fine: r = 0.1 – 0.5 mm coarse: r = 0.5 – 10 mm This can be easily changed (i.e. 2.5 mm) in input.geos. Details of sea-salt budget are in Alexander et al., 2005 (on web site)

  3. Subsidence other aerosols (acid or neutral) NH3(g) RCOOH(g) HNO3(g) Sea-salt pH=8 HCO3-/CO32- O3 Deposition CO2(g) Emission GEOS-CHEM Sea-salt chemistry Details of sea-salt chemistry are in Alexander et al., 2005 (on web site) Free troposphere Marine Boundary Layer Subsidence Cloud SO42- H2O2 H2SO4(g) OH SO2 OH NO3 DMS Emission

  4. INDOEX Cruises Extra sulfate tracers Isotope version: Primary SO42-D17O=0‰ SO2 + OH D17O=0‰ S(IV) + H2O2D17O=0.9‰ S(IV) + O3D17O=8.8‰ (in-cloud, SALA, SALC) Standard version: SO4S (sulfate formed in coarse sea-salt aerosols from S(IV) + O3) SO4 (all other sulfate) January 1997 March 1998

  5. GEOS-CHEM Sulfur Budget [SO2] % decrease [SO42-] % increase SO2 + OH % decrease 10 30 50 70 5

  6. Aerosol Thermodynamics RPMARES ISOROPIA Saxena et al., 1986; Kim et al., 1993 Nenes et al., 1998 SO4-NO3-NH4-H2O SO4-NO3-NH4-Na-Cl-H2O HSO4-, SO42- HSO4-, SO42- HCl Na+ Cl- NO3- NH4+ NH4+ NO3- NH3 HNO3 NH3 HNO3

  7. Effects of Sea-salt chemistry and ISOROPIA on HNO3 and NO3- HNO3 NO3- Absolute Difference -4 0 4 ppbv % Difference 0 -100 100 % 0

  8. Effects of Sea-salt chemistry and ISOROPIA on NH3 and NH4 NH4+ NH3 Absolute Difference -7 0 7 ppbv % Difference 0 -100 100 % 0

  9. 90 N 60 N 60 30 N 0 30 S 60 S 30 90 S 5 June 0 2 4 6 8 10 12 14 16 DMS concentration (nM) Future Model Development Plans: DMS Seawater DMS concentrations Old: Kettle et al. [1999] New: Simó and Dachs [2002] DMS sea-air transfer function Wanninkhov&McGillis [1999] Wanninkhov et al. [1992] Nightingale et al. [2000] Liss&Merlivat [1986] SeaWiFS DMS Chemistry (DMS+BrO) Boucher et al. [2003] DMS = f(Chl/MLD) % DMS oxidation rate

  10. Extra slides

  11. GEOS-CHEM Alkalinity Budget fSO2 fHNO3 fexcess 0.1 0.3 0.5 0.7

  12. Sensitivity simulation: Excess alkalinity 2OH• nssSO42-D17O (‰) Observations Model with excess alkalinity Na+, Cl- Cl2 Latitude (°N) Laskin et al., 2003 2OH- OH(g) + Cl-(interface) (HO…Cl-)interface (HO…Cl-)interface +(HO…Cl-)interface  Cl2 + 2OH-

  13. Transfer rate constant [Schwartz, 1986]

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