Sulfate aerosols

On this page we provide information about the sulfate aerosol species in GEOS-Chem. Note that in GEOS-Chem v10-01 and higher versions, all emissions of sulfate aerosols are now handled by the HEMCO emissions component.

Overview

Original formulation

From Park et al [2004]:

The sulfur simulation in GEOS-Chem is based on the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model [Chin et al., 2000a], with a number of modifications described below. Our fossil fuel and industrial emission inventory is for 1999-2000 and is obtained by scaling the gridded, seasonally resolved inventory from the Global Emissions Inventory Activity (GEIA) for 1985 [Benkovitz et al., 1996] with updated national emission inventories and fuel use data [Bey et al., 2001a]. The emissions for the United States and Canada are from U.S. EPA [2001], and the emissions for European countries are from European Monitoring and Evaluation Programme (EMEP)/United Nations Economic Commission for Europe (UNECE). Asian sulfur emission in the model is 20 Tg S yr1, which can be compared to year 2000 estimates of 17 Tg S yr1 by Streets et al. [2003] and 25 Tg S yr1 by Intergovernmental Panel on Climate Change (hereinafter IPCC) [2001]. Anthropogenic sulfur is emitted as SO2 except for a small fraction as sulfate (5% in Europe and 3% elsewhere) [Chin et al., 2000a].

Other anthropogenic sources of SO2 in the model include gridded monthly aircraft emissions (0.07 Tg S yr1) taken from Chin et al. [2000a] and biofuel use. We use a global biofuel CO emission inventory with 1° x 1° spatial resolution from Yevich and Logan [2003] and apply an emission factor of 0.0015 mol SO2 per mole CO [Andreae and Merlet, 2001]. Seasonal variations in biofuel emissions are specified from the heating degree days approach [Park et al., 2003].

Natural sources of sulfur in the model include DMS from oceanic phytoplankton and SO2 from volcanoes and biomass burning. The oceanic emission of DMS is calculated as the product of local seawater DMS concentration and sea-to-air transfer velocity. The seawater DMS concentrations are gridded monthly averages from Kettle et al. [1999], and the transfer velocity of DMS is computed using an empirical formula from Liss and Merlivat [1986] as a function of the surface (10 m) wind speed. The GEOS surface winds used here assimilate remote sensing data from the Special Sensor Microwave Imager instrument. Volcanic emissions of SO2 from continuously active volcanoes are included from the database of Andres and Kasgnoc [1998]. Emissions from sporadically erupting volcanoes show large year-to-year variability and are not included in the model. No major volcanic eruptions occurred in 2001. Biomass burning emissions of SO2 are calculated using a gridded monthly biomass burning inventory of CO constrained from satellite observations in 2001 by Duncan et al. [2003] with an emission factor of 0.0026 mol SO2 per mole CO [Andreae and Merlet, 2001].

The gas-phase sulfur oxidation chemistry in the model includes DMS oxidation by OH to form SO2 and MSA, DMS oxidation by nitrate radicals (NO3) to form SO2, and SO2 oxidation by OH to form sulfate. Reaction rates are from DeMore et al. [1997] and the yields of SO2 and MSA from DMS oxidation are from Chatfield and Crutzen [1990]. Aqueous-phase oxidation of SO2 by O3 and H2O2 in clouds to form sulfate is included using kinetic data from Jacob [1986] and assuming a pH of 4.5 for the oxidation by O3. Cloud liquid water content is not available in the GEOS data, and we specify it instead in each cloudy grid box by using a temperature-dependent parameterization [Somerville and Remer, 1984]. The cloud volume fraction in a given grid box is specified as an empirical function of the relative humidity following Sundqvist et al. [1989].

Ammonia emissions in the model are based on annual data for 1990 from the 1° x 1° GEIA inventory of Bouwman et al. [1997]. Source categories in that inventory include domesticated animals, fertilizers, human bodies, industry, fossil fuels, oceans, crops, soils, and wild animals. We view the first five as anthropogenic and the last four as natural. Additional emissions from biomass burning and biofuel use are computed using the global inventories of Duncan et al. [2003] and Yevich and Logan [2003], with an emission factor of 1.3 g NH3 per kilogram dry mass burned [Andreae and Merlet, 2001].

Production of total inorganic nitrate (gas-phase nitric acid and aerosol nitrate) in the model is computed from the ozone-NOx-hydrocarbon chemical mechanism.

Important updates to the sulfate aerosol simulation

Notable additions since Park et al [2004]:

1. Biomass emissions of SO2 and NH3 are now computed by the GFED inventory.
   • The most recent version (Oct 2015) is GFED4
   • You may still uses the older GFED2 or GFED3 inventories for research purposes.
2. Incorporation of new Volcanic SO2 emissions from Aerocom
3. Alkalinity computation for Sea salt aerosols
4. Updates to regional and global anthropogenic emissions inventories
5. Get liquid water content and cloud fraction directly from GEOS-5 met fields for SO2 chemistry (since GEOS-Chem v8-03-02)
6. Other minor changes

Also, the following updates have been added (or are in the process of being added) since GEOS-Chem v9-02:

--Bob Y. (talk) 15:34, 26 October 2015 (UTC)

Cloud water pH for sulfate formation

This update was tested in the 1-month benchmark simulation v9-02p and approved on 13 Sep 2013.

Becky Alexander wrote:

Bulk cloud pH is calculated iteratively using concentrations of sulfate, total nitrate (HNO3 + NO3), total ammonia (NH3 + NH4), SO2, and CO2 = 390 ppmv based on their effective Henry's law constants and the local cloud LWC.

Over the oceans, the influence of cloud droplet heterogeneity in pH on in-cloud sulfate production rates is accounted for using the Yuen et al. (1996) parameterization. Based on isotopic evidence, this parameterization seems to work well over the oceans using sea salt aerosol as the course mode aerosol component, but tends to overestimate in-cloud sulfate production over land.

The reference for this work is:

Alexander, B., D.J. Allman, H.M. Amos, T.D. Fairlie, J. Dachs, D.A. Hegg and R.S. Sletten, Isotopic constraints on sulfate aerosol formation pathways in the marine boundary layer of the subtropical northeast Atlantic Ocean, J. Geophys. Res., 117, D06304, doi:10.1029/2011JD016773, 2012.

--Melissa Sulprizio 11:55, 5 September 2013 (EDT)

Update DMS climatology to Lana

This update was validated with 1-month benchmark simulation v11-01b and 1-year benchmark simulation v11-01b-Run0. This version was approved on 19 Aug 2015.

Monthly average DMS seawater concentrations at 1° x 1° resolution will be implemented in GEOS-Chem v11-01 (via the HEMCO emissions component). These data are described in Lana et al. (2011).

--Melissa Sulprizio (talk) 19:23, 20 July 2015 (UTC)

Tagged sulfate and nitrate simulation

This update is slated for inclusion in GEOS-Chem v11-01.

Becky Alexander wrote:

Sulfate and nitrate each have several different tracers that correspond to their production pathway. This allows for an off-line calculation of their oxygen isotopes (O-17 excess), and allows one to determine the relative importance of each production pathway to the burden of sulfate and nitrate.

--Melissa Sulprizio (talk) 20:50, 15 June 2015 (UTC)

Metal catalyzed oxidation of SO2

This update is slated for inclusion in GEOS-Chem v11-01.

Becky Alexander wrote:

SO2 is oxidized in clouds by transition metals (Fe and Mn). Natural Fe and Mn atmospheric concentrations are scaled to dust, and anthropogenic are scaled to primary anthropogenic sulfate. It is assumed that 1% of natural Mn and Fe is soluble, for anthropogenic it is 10%. The oxidation state of Fe and Mn depends on sunlight. See Alexander et al. [2009] for more details.

Reference:

Alexander, B., Park, R.J., Jacob, D.J., and Gong, S., Transition metal catalyzed oxidation of atmospheric sulfur: Global implications for the sulfur budget, J. Geophys. Res., 114, D02309, 2009.

--Melissa Sulprizio (talk) 20:50, 15 June 2015 (UTC)

Ocean ammonia emission inventory

This update is slated for inclusion in GEOS-Chem v11-01.

Fabien Paulot and others have created a new emission inventory for ammonia from oceans. The reference for this work is

Paulot, F., D.J. Jacob, M. Johnson, T.G. Bell, A.R. Baker, W.C. Keene, I.D. Lima, S.C. Doney, and C.A. Stock, Global oceanic emission of ammonia: constraints from seawater and atmospheric observations, Global Biogeochemical Cycles, in press, 2015. [ PDF ]

These emissions will be implemented into GEOS-Chem v11-01 via the HEMCO emissions component.

--Melissa Sulprizio (talk) 17:50, 4 August 2015 (UTC)

Source code and data

In GEOS-Chem versions prior to v10-01

For GEOS-Chem versions prior to v10-01, the source code for reading in the anthropogenic and aircraft emissions was contained sulfate_mod.f.

Emissions inventories included:

1. DMS seawater concentrations [nm/ML] from Andreae
2. NH3 anthropogenic emissions for year 1990 [kg N/month] from GEIA
3. NH3 biofuel emissions for year 1998 [kg NH3/month] from Park et al. [2004]
4. NH3 natural-source emissions for year 1990 [kg N/month] from GEIA
5. SO2 emissions from aircraft [kg/day] from Chin et al [2000].
6. Various ship emissions inventories
7. Volcanic emissions of SO2

For more information about the sulfate emissions data files, please see the following READMEs:

1. GEOS_0.5x0.666_CH/sulfate_sim_200508/README
2. GEOS_0.5x0.666_NA/sulfate_sim_200508/README
3. GEOS_2x2.5/sulfate_sim_200508/README
4. GEOS_4x5/sulfate_sim_200508/README

--Bob Y. 14:31, 12 March 2010 (EST)

In GEOS-Chem v10-01 and higher versions

In GEOS-Chem v10-01 and newer versions, the sulfate emissions data files are read with the HEMCO emissions component. We have created new data files (in COARDS-compliant netCDF format) for use with HEMCO. These new data files are contained in the HEMCO data directory tree. For detailed instructions on how to download these data files to your disk server, please see our Downloading the HEMCO data directories wiki post.

--Melissa Sulprizio (talk) 19:17, 20 July 2015 (UTC)

References

1. Andreae, M. O., and P. Merlet (2001), Emission of trace gases and aerosols from biomass burning, Global Biogeochem. Cycles, 15(4), 95596
2. Andres, R. J., and A. D. Kasgnoc, A time-averaged inventory of subaerial volcanic sulfur emissions, J. Geophys. Res., 103(D19), 25,251-25,261, 1998.
3. Benkovitz, C. M., M. T. Scholtz, J. Pacyna, L. Tarrason, J. Dignon, E. C. Voldner, P. A. Spiro, J. A. Logan, and T. E. Graedel, Global gridded inventories of anthropogenic emissions of sulfur and nitrogen, J. Geophys. Res., 101(D22), 29,239-29,253, 1996.
4. Bey, I., D. J. Jacob, R. M. Yantosca, J. A. Logan, B. Field, A. M. Fiore, Q. Li, H. Liu, L. J. Mickley, and M. Schultz, Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23,073-23,096, 2001. PDF
5. Bouwman, A. F., D. S. Lee, W. A. H. Asman, F. J. Dentener, K. W. VanderHoek, and J. G. J. Olivier, A global high-resolution emission inventory for ammonia, Global Biogeochem. Cycles, 11(4), 561-587, 1997.
6. Chatfield, R. B., and P. J. Crutzen, Are there interactions of iodine and sulfur species in marine air photochemistry?, J. Geophys. Res., 95(D13), 22,319-22,341, 1990.
7. DeMore, W. B., S. P. Sander, D. M. Golden, R. F. Hampson, M. J. Kurylo, C. J. Howard, A. R. Ravishankara, C. E. Kolb, and M. J. Molina, Chemical kinetics and photochemical data for use in stratospheric modeling, JPL Publ., 97-4, 1-278., 1997.
8. Duncan, B. N., R. V. Martin, A. C. Staudt, R. Yevich, and J. A. Logan, Interannual and seasonal variability of biomass burning emissions constrained by satellite observations, J. Geophys. Res., 108(D2), 4100, doi:10.1029/2002JD002378, 2003. PDF
9. Jacob, D. J., Chemistry of OH in remote clouds and its role in the production of formic acid and peroxymonosulfate,J. Geophys. Res., 91(D9), 9807-9826, 1986.
10. Kettle, A. J., et al. A global database of sea surface dimethylsulfide (DMS) measurements and a procedure to predict sea surface DMS as a function of latitude, longitude, and month, Global Biogeochem. Cycles, 13(2), 399-444., 1999.
11. Liss, P. S., and L. Merlivat (1986), Air-sea gas exchange rates: Introduction and synthesis, in The Role of Air-Sea Exchange in Geochemical Cycling, edited by P. Buat-Me´nard, pp. 113-127, D. Reidel, Norwell, Mass, 1986.
12. Park, R. J., D. J. Jacob, B. D. Field, R. M. Yantosca, and M. Chin, Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: implications for policy, J. Geophys. Res., 109, D15204, 10.1029/2003JD004473, 2004. PDF
13. Yevich, R., and J. A. Logan, An assessment of biofuel use and burning of agricultural waste in the developing world, Global Biogeochem. Cycles, 17(4), 1095, doi:10.1029/2002GB001952, 2003. PDF
14. Somerville, R. C. J., and L. A. Remer, Cloud optical thickness feedbacks in the CO2 climate problem, J. Geophys. Res., 89(D6), 9668-9672, 1984.
15. Streets, D. G., et al. An inventory of gaseous and primary aerosol emissions in Asia in the year 2000, J. Geophys. Res., 108(D21), 8809, doi:10.1029/2002JD003093, 2003.

--Bob Y. 14:36, 23 February 2010 (EST)

Previous issues that have now been resolved

The following bugs and/or technical issues in the sulfate aerosol module have since been resolved:

Give SO4s and NITs the same molecular weight as SALC

This update was validated with 1-month benchmark simulation v11-01e (approved 04 Jan 2016).

For several past GEOS-Chem versions, SO4s and NITs had the wrong molecular weights listed in the input.geos file.

Bob Yantosca wrote:

In GEOS-Chem v9-02, we changed the molecular weights of the sea salt species SALA and SALC in the input.geos file from 0.036 kg/mol to 0.0314 kg/mol. But somehow this change never got propagated to drydep_mod.F, where we were still using the old molecular weight of 0.036 kg/mol. This is now fixed in the GEOS-Chem v11-01e development code.

One question that I still have is this: What should we use for the MW’s of SO4s and NITs in drydep_mod.F? Both of these species currently use molecular weights of 0.036 kg/mol in drydep_mod.F. (This was the old sea salt molecular weight prior to v9-02.) But the actual molecular weight of SO4s is 0.096 kg/mol and that of NITs is 0.062 kg/mol. So for dry deposition purposes, should we use the MW of sea salt, or should we use the actual MW’s of SO4s and NITs? I looked back throughout the code but could not find any comments documenting this. This behavior has been in the code at least through v7-03-01, and probably earlier.

Becky Alexander replied:

The reason for using sea salt's molecular weight for SO4s and NITs is that these tracers are essentially internally mixed with coarse sea salt aerosol (SALC). As coarse sea salt aerosol likely dominates the mass of these aerosols, it is appropriate to use sea salt's MW.

Another explanation is that since SO4s and NITs are internally mixed with sea salt, they should be treated identically to SALC in the code for all processes.

Therefore, in GEOS-Chem v11-01e, we have changed the molecular weights of SO4s and NITs to 31.4 g/mol in the GEOS-Chem species database. These values will be used everywhere throughout GEOS-Chem.

--Bob Yantosca (talk) 19:25, 15 December 2015 (UTC)

Bug fix for sea salt alkalinity in sulfate_mod.F

This fix was validated with the 1-month benchmark simulation v11-01c and approved on 14 Sept 2015.

Johan Schmidt wrote:

There is a bug in the GET_ALK subroutine (now part of sulfate_mod) that causes the computed rate of uptake of SO2 and HNO3 on to sea salt aerosol to be much too slow. GET_ALK only considers the surface area of freshly emitted sea salt (contained in N1 and N2) when calculating the rate, it should consider the surface area of all sea salt aerosols in the grid box.

The bug results in too low sulfate formation, and retained SSA alkalinity in regions that should have acidic SSA.

I would like to propose a fix where the uptake rates (KT1, KT2, KTN1, and KTN2) are calculated using the SSA surface area (from TAREA) and effective radius (from ERADIUS).

I have outlined the bug fix below.

I've added the following variable to GET_ALK

     JLOOP = JLOP(I,J,L)

     SA1= TAREA(JLOOP,4+NDUST) !in cm2/cm3
     SA2= TAREA(JLOOP,5+NDUST) !in cm2/cm3

     R1 = ERADIUS(JLOOP,4+NDUST) !in cm
     R2 = ERADIUS(JLOOP,5+NDUST) !in cm

I've then modified the section that calculates KT1, KT2, KTN1, KTN2 as below:

        ! calculate gas-to-particle rate constant for uptake of 
        ! SO2 onto fine sea-salt aerosols [Jacob, 2000] analytical solution
        CONST1 = 4.D0/(V*GAMMA_SO2)
        !A1     = (RAD1/DG)+CONST1
        !B1     = (RAD2/DG)+CONST1
        !TERM1A = ((B1**2)/2.0d0) - ((A1**2)/2.0d0)
        !TERM2A = 2.D0*CONST1*(B1-A1)
        !TERM3A = (CONST1**2)*LOG(B1/A1)
        !KT1    = 4.D0*PI*N1*(DG**3)*(TERM1A - TERM2A + TERM3A)
        KT1    = SA1/((R1/DG) + CONST1)
        
        !----------------------------------
        ! SO2 uptake onto coarse particles 
        !----------------------------------
        
        ! calculate gas-to-particle rate constant for uptake of 
        ! SO2 onto coarse sea-salt aerosols [Jacob, 2000] analytical solution
        CONST2 = 4.D0/(V*GAMMA_SO2)
        !A2     = (RAD2/DG)+CONST2
        !B2     = (RAD3/DG)+CONST2
        !TERM1B = ((B2**2)/2.0d0) - ((A2**2)/2.0d0)
        !TERM2B = 2.D0*CONST2*(B2-A2)
        !TERM3B = (CONST2**2)*LOG(B2/A2)
        !KT2    = 4.D0*PI*N2*(DG**3)*(TERM1B - TERM2B + TERM3B)
        KT2    = SA2/((R2/DG) + CONST2)
        KT     = KT1 + KT2
        
        !----------------------------------
        ! HNO3 uptake onto fine particles 
        !----------------------------------
        
        ! calculate gas-to-particle rate constant for uptake of 
        ! HNO3 onto fine sea-salt aerosols [Jacob, 2000] analytical solution
        CONST1N = 4.D0/(V*GAMMA_HNO3)
        !A1N     = (RAD1/DG)+CONST1N
        !B1N     = (RAD2/DG)+CONST1N
        !TERM1AN = ((B1N**2)/2.0d0) - ((A1N**2)/2.0d0)
        !TERM2AN = 2.D0*CONST1N*(B1N-A1N)
        !TERM3AN = (CONST1N**2)*LOG(B1N/A1N)
        !KT1N    = 4.D0*PI*N1*(DG**3)*(TERM1AN - TERM2AN + TERM3AN)
        KT1N    = SA1/((R1/DG) + CONST1N)
        
        !----------------------------------
        ! HNO3 uptake onto coarse particles 
        !----------------------------------
        
        ! calculate gas-to-particle rate constant for uptake of 
        ! HNO3 onto coarse sea-salt aerosols [Jacob, 2000] analytical solution
        CONST2N = 4.D0/(V*GAMMA_HNO3)
        !A2N     = (RAD2/DG)+CONST2N
        !B2N     = (RAD3/DG)+CONST2N
        !TERM1BN = ((B2N**2)/2.0d0) - ((A2N**2)/2.0d0)
        !TERM2BN = 2.D0*CONST2N*(B2N-A2N)
        !TERM3BN = (CONST2N**2)*LOG(B2N/A2N)
        !KT2N    = 4.D0*PI*N2*(DG**3)*(TERM1BN - TERM2BN + TERM3BN)
        KT2N    = SA2/((R2/DG) + CONST2N)

--Melissa Sulprizio (talk) 15:22, 3 August 2015 (UTC)

Bug fix for NEI2005 SO4 emissions in sulfate_mod.F

This update was included as a last-minute fix in GEOS-Chem v9-02 (public release 03 Mar 2014).

Please see this post on our EPA/NEI05 North American emissions wiki page for more a complete description of the issue.

--Melissa Sulprizio 12:15, 13 December 2013 (EST)

Updated THNO3.geos4.4x5 file

Lyatt Jaegle wrote:

I was trying to run GEOS-Chem (v8-01-03) in the offline aerosol mode with GEOS-4 met fields and ran into a problem: it seems that the offline file GEOS_4x5/sulfate_sim_200508/offline/THNO3.geos4.4x5 is in units of ppbv instead of v/v as expected in routine GET_HNO3_UGM3. This leads to issues in RPMARES which thinks that HNO3 is very large. I checked all the other files, and they are in v/v, as expected.

Bob Yantosca wrote:

Thanks Lyatt. I've downloaded the file and updated the README in the GEOS_4x5/sulfate_sim_200508/offline directory.

--Bob Y. 14:19, 24 April 2009 (EDT)

Fix for mass balance of HNO3 and NIT

NOTE: This fix is was standardized in GEOS-Chem v8-01-02.

Becky Alexander wrote:

We need to make a change in sulfate_mod in order to have mass balance for HNO3 and NIT. Duncan Fairlie noticed the bug. There is a simple change:

In routine SEASALT_CHEM in sulfate_mod.f: In order to have mass balance, you need to change:

   !HNO3 lost [eq/timestep] converted back to [v/v/timestep]
   HNO3_ss = TITR_HNO3 * 0.063 * TCVV(IDTHNO3)/AD(I,J,L)

to:

   !HNO3 lost [eq/timestep] converted back to [v/v/timestep]
   HNO3_ss = HNO3_SSC * 0.063 * TCVV(IDTHNO3)/AD(I,J,L)

In my original code where I added isorropia and the new tracers, NITs and SO4s, the line above:

   !HNO3 lost [eq/timestep] converted back to [v/v/timestep]
   HNO3_ss = TITR_HNO3 * 0.063 * TCVV(IDTHNO3)/AD(I,J,L)

is appropriate as long as you also have PNIT (analogous to PNITs). PNIT is in my original code where I did all my mass balance testing. PNIT got dropped when going to the standard version. I don't recall dropping this, but my guess is that I decided it was redundant to have it when isorropia would just repartition HNO3 and NIT anyway according to thermodynamic equilibrium. But when dropping PNIT, you have to change TITR_HNO3 to HNO3_SSC in the above equation in order to achieve mass balance.

--Bob Y. 16:36, 19 February 2010 (EST)