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Global ammonium aerosol chemistry and distribution: Relationship to sulfate, nitrate,
seasalt, and dust aerosols
Huisheng Bian
GEST/UMBC, GSFC/NASA
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