Global ammonium aerosol chemistry and distribution: Relationship to sulfate, nitrate,

seasalt, and dust aerosols

Huisheng Bian

GEST/UMBC, GSFC/NASA

bian@rondo.gsfc.nasa.gov

Charlie Zender University of California Irvine

Objectives

• Understand the major features of global ammonium distributions and their relationship to sulfate, nitrate, seasalt, and dust aerosols.

• Identify the chemical feedback on sulfur chemistry and

sulfate distribution when heterogeneous reactions are

implemented in a unified framework of interactive

aerosols including sulfate, nitrate, ammonium, dust,

and seasalt.

• Examine the effect of ammonia nitrogen reservoir on

the uptake of nitrogen by dust and seasalt.

Tools

1. UCI Chemistry Transport Model (see next slide)

2. Dust module global Dust Entrainment And Deposition (DEAD) model

ftp://dust.ps.uci.edu/pub/zender/ppr/ppr_ZBN03.pdf

5. Seasalt module

Grini et al., 2002, Journal of Climate, vol. 15, pp 1717-1730

7. Thermodynamic gas/aerosol module

EQuilibrium Simplified Aerosol Model (EQSAM)

Metzger et al., 2002, JGR, vol. 107, No. 16

UCI CTM

• Met-fields: GISS GCM II' with 4○x5○ x 9 resolution upgrade every three hours• Same resolution as GCM• An O3-NOx-NMHC-SO2 chemical scheme with 41 species, 95 chemical

reactions, 19 photochemical reactions, and 9 aqueous reactions

• Upgraded with ammonia chemistry, dust and seasalt modules, and a thermodynamic equilibrium module for gas/aerosol partitioning

• Trace-gas emissions from GEIA with updated total amounts from the IPCC

• Wet scavenging for large-scale: a first order rainout parameterization for large scale precipitation

Wet scavenging for convection: convective mass transport operator• Dry deposition: resistance-in-series• Advection scheme: second-order moments• Radiation model: Fast-J (AEROSOL: τ, ώ, phase function)

Approach

Three experiments are designed to assist the analysis of ammonia chemistry:

• Exp. A: tropospheric NOx-O3-NMHC-SO2-NH3 chemistry, as well as dust

and seasalt modules H2SO4/SO=

4, HNO3/NO-3, NH3/NH+

4, dust, and seasalt included in

the EQSAM dust heterogeneous uptake for O3, NO3, NO2, N2O5, HO2, H2O2,

and SO2 calculated outside of EQSAM

• Exp. B: tropospheric NOx-O3-NMHC-SO2-NH3 chemistry, as well as dust

module only H2SO4/SO=

4, HNO3/NO-3, and NH3/NH+

4 included in EQSAM

dust heterogeneous uptake for HNO3, O3, NO3, NO2, N2O5,HO2,

H2O2, and SO2 calculated outside of EQSAM

• Exp. C: tropospheric NOx-O3-NMHC-SO2 chemistry, without ammonia

chemistry and dust and seasalt modules.

All experiments run for 18 months and are diagnosed for the last 12 months. All analyses are for global troposphere.

Aerosol surface distributions

Units: μg SO4/m3 for sulfate, μg NO3/m3 for nitrate, and μg NH4/m3 for ammonium

Model-measurement comparisons of aerosol surface annual average concentrations

Units: μg S/m3 for SO=4, μg N/m3 for NO-

3 and NH+4. Thin lines indicate 2:1 and 1:2 ratios.

Model-measurement comparisons of aerosol seasonal changes

Units: μg S/m3 for SO=4, μg N/m3 for NO-

3 and NH+4.

Solid green line: Exp. A; Dash-dot red line: Exp. C; Dots: measurements.

Model-measurement comparisons of aerosol seasonal changes

Units: μg S/m3 for SO=4, μg N/m3 for NO-

3 and NH+4.

Solid green line: Exp. A; Dash-dot red line: Exp. C; Dots: measurements.

6.26.45.5NO3ˉ

1.11.11.21.1DMS

1.10.91.71.4SO2

4.54.23.65.39.0NH4+

2.10.90.50.61.0NH3

5.24.94.95.8SO4=

-3.93.74.1MSA

13.11.62.02.3HNO3

Dentener

1994Adam 1999

6.4

Rodriguez 2003

0.5

Exp. C

0.5

Exp. B

0.5

Exp. A

NOX

lifetime tracer

Lifetimes of nitrogen, sulfur, and ammonia

Units: day. Exp. A, B, and C refer to approach.

21.6

3.2

5.9

12.5

Dentener 1994

01.1000wet

1.2 (0.7-5.8)14.610.921.421.2wet

31.423.827.531.2wet

8.4 (6.9-12.3)0.78.57.7wet

dry

dry

dry

dry

wet

dry

Wet

dry

0.044.21.10.90.9NOx

1.9 (0.5-7.8)6.67.72.71.4NH4

+

11.4 (4.6-38.9)19.519.329.018.6

1.0 (0.7-3.3)14.34.75.78.5HNO3

6.53.82.12.4SO4

=

2.8 (1.9-9.4)0.21.13.5NO3

ˉ

3.4(0.51-10.4)7.43.312.918.7

Duce et al. 1991

19.5

Adam 1999

21.2

Rodriguez 2002

Exp. C

13.4

Exp. B

19.5

Exp. A

NH3

Dry and wet depositions of nitrogen, sulfur, and ammonia

Units: TgN/yr for nitrogen, TgS/yr for sulfur. The depositions of Duce represent global nitrogen deposition to the global ocean.

Conclusions

•The surface maxima of aerosol (SO=4, NO-

3, NH+4) abundances coincide in east

Asia and Europe in January. In July, the maximum surface abundance of SO=4

shifts to the southeast of Europe, NO-3 to west Europe, and NH+

4 to south Europe.

•Simulated aerosol abundances agree well with the measurements in polluted regions (North American and European). The simulations capture the aerosol seasonality.

•Sulfate simulations are improved, specially in the Northern Hemisphere high latitudes, by accounting dust, seasalt, nitrate, and ammonium aerosols in the model.

•Tropospheric lifetimes of ammonia and ammonium are almost doubled when coarse natural aerosols, seasalt and dust, are joined in gas/aerosol partitioning determined by the thermodynamic equilibrium module.

•The additional nitrogen reservoir (ammonia) increases the tropospheric lifetime of nitric acid by 15% relative to the experiment with uptake on dust and seasalt excluded from EQSAM.

Future work

•Further analyses to understand the relationship between tracer emissions, chemistry, transport, depositions, and aerosol abundances

•Describing the partitioning of inorganic nitrogen between ammonium sulfate and ammonium nitrate, and their deposition fluxes

•The tendencies of global sulfate and nitrate burdens with year 2100 emission scenarios of IPCC SRES

•Carbonaceous aerosol upgraded

•The climate impact of all major aerosols, specially nitrate, at present and year 2100