Sea-salt aerosol chemistry in GEOS-CHEM

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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. - PowerPoint PPT Presentation

Text of Sea-salt aerosol chemistry in GEOS-CHEM

  • Sea-salt aerosol chemistry in GEOS-CHEMBecky AlexanderRokjin Park, Daniel Jacob, Bob Yantosca1) Sea-salt emissions2) Sea-salt/sulfate chemistry O-isotopes3) New aerosol thermodynamics NO3-, NH4+4) DMS (concentrations, emissions, chemistry)

  • GEOS-CHEM Sea-salt aerosol simulationdF/dr = 1.373u103.41r-3(1+0.057r1.05)101.19exp(-B2) = (0.380 log r)/0.65Monahan et al., 1986 (particles m-2 s-1 mm-1)2 size bins (SALA & SALC)fine: r = 0.1 0.5 mmcoarse: r = 0.5 10 mmThis 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)

  • GEOS-CHEM Sea-salt chemistryDMSSO2Free troposphereH2SO4(g)OH Cloud H2O2 EmissionMarine Boundary LayerSubsidenceOH NO3SO42-Details of sea-salt chemistry are in Alexander et al., 2005 (on web site)

  • INDOEX CruisesJanuary 1997March 1998Extra sulfate tracersIsotope version:Primary SO42- D17O=0SO2 + OH D17O=0S(IV) + H2O2 D17O=0.9S(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)

  • GEOS-CHEM Sulfur Budget

  • Aerosol ThermodynamicsRPMARESISOROPIANO3-NH4+NH3HNO3HSO4-, SO42-NO3-NH4+HNO3HSO4-, SO42-Cl-Na+NH3HClNenes et al., 1998Saxena et al., 1986; Kim et al., 1993SO4-NO3-NH4-H2OSO4-NO3-NH4-Na-Cl-H2O

  • Effects of Sea-salt chemistry and ISOROPIA on HNO3 and NO3-04 ppbv-4HNO3 Absolute Difference% Difference0100 %-100NO3-0

  • Effects of Sea-salt chemistry and ISOROPIA on NH3 and NH407 ppbv-7NH4+ Absolute Difference% Difference0100 %-100NH30

  • Future Model Development Plans: DMSSeawater DMS concentrationsOld: Kettle et al. [1999]New: Sim and Dachs [2002]DMS sea-air transfer functionDMS Chemistry (DMS+BrO)Boucher et al. [2003]% DMS oxidation rateWanninkhov&McGillis [1999]Wanninkhov et al. [1992]Nightingale et al. [2000]Liss&Merlivat [1986]DMS = f(Chl/MLD)SeaWiFS

  • Extra slides

  • GEOS-CHEM Alkalinity Budget

  • Sensitivity simulation: Excess alkalinityOH(g) + Cl-(interface) (HOCl-)interface (HOCl-)interface + (HOCl-)interface Cl2 + 2OH-2OH-Laskin et al., 2003

  • Transfer rate constant [Schwartz, 1986]

    SO2 transfer rate constantUptake of all species are limited by transfer to aerosol surface. We estimate the uptake rate of H2SO4 from the production rate. Gas phase MBL HNO3 in standard version is biased high since we dont include uptake on sea-salt. So I estimate the uptake rate from the deposition flux to the ocean surface.RPMARES: 2 regimesAmmonia rich: all sulfate is NH4HSO4; Free NH3 and HNO3 are partitioned between gas and aerosol phase w/equilibrium calculation using their concentrations, aerosol water content, and temperature in 3 RH regimesAmmonia poor: All ammonia is in aerosol phase, all nitrate is in gas phaseISOROPIA: 4 regimesSulfate rich free acid (Rso4