General circulation model assessment of direct radiative forcing by the sulfate-nitrate-ammonium-water inorganic aerosol system. Adams, P., J., Seinfeld, J., H., Koch, D., Mickley, L., & Jacob, D. J. Geophys. Res.-Atmos., 106:1097-1111, 2001.
abstract   bibtex   
An on-line simulation of aerosol sulfate, nitrate, ammonium, and water in the Goddard Institute for Space Studies general circulation model (GCM II-prime) has been used to estimate direct aerosol radiative forcing for the years 1800, 2000, and 2100. This is the first direct forcing estimate based on the equilibrium water content of a changing SO42-NO3--NH4+ mixture and the first estimate of nitrate forcing based on a global model of nitrate aerosol, Present-day global and annual average anthropogenic direct forcing is estimated to be -0.95 and -0.19 W/m(2) for sulfate and nitrate, respectively. Simulations with a future emissions scenario indicate that nitrate forcing could increase to -1.28 W/m(2) by 2100, while sulfate forcing declines to -0.85 W/m(2). This result shows that future estimates of aerosol forcing based solely on predicted sulfate concentrations may be misleading and that the potential for significant concentrations of ammonium nitrate needs to be considered in estimates of future climate change. Calculated direct aerosol forcing is highly sensitive to the model treatment of water uptake. By calculating the equilibrium water content of a SO42--NH4+ aerosol mixture and the optical properties of the wet aerosol, we estimate a forcing that is almost 35% greater than that derived from correcting a low relative humidity scattering coefficient with an empirical f(RH) factor. The discrepancy stems from the failure of the empirical parameterization to adequately account for water uptake above about 90% relative humidity. These results suggest that water uptake above 90% RH may make a substantial contribution to average direct forcing, although subgrid-scale variability makes it difficult to represent humid areas in a GCM. C1 CALTECH, Dept Chem, Pasadena, CA 91125 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Harvard Univ, Div Engn & Appl Sci, Cambridge, MA 02138 USA.
@article{
 title = {General circulation model assessment of direct radiative forcing by the sulfate-nitrate-ammonium-water inorganic aerosol system},
 type = {article},
 year = {2001},
 pages = {1097-1111},
 volume = {106},
 id = {ee3e2277-56a2-3a09-9239-1a49970d1697},
 created = {2014-10-08T16:28:18.000Z},
 file_attached = {false},
 profile_id = {363623ef-1990-38f1-b354-f5cdaa6548b2},
 group_id = {02267cec-5558-3876-9cfc-78d056bad5b9},
 last_modified = {2017-03-14T17:32:24.802Z},
 read = {false},
 starred = {false},
 authored = {false},
 confirmed = {true},
 hidden = {false},
 citation_key = {Adams:JGRA:2001a},
 source_type = {article},
 private_publication = {false},
 abstract = {An on-line simulation of aerosol sulfate, nitrate,
ammonium, and water in the Goddard Institute for Space Studies
general circulation model (GCM II-prime) has been used to estimate
direct aerosol radiative forcing for the years 1800, 2000, and
2100. This is the first direct forcing estimate based on the
equilibrium water content of a changing SO42-NO3--NH4+ mixture and
the first estimate of nitrate forcing based on a global model of
nitrate aerosol, Present-day global and annual average
anthropogenic direct forcing is estimated to be -0.95 and -0.19
W/m(2) for sulfate and nitrate, respectively. Simulations with a
future emissions scenario indicate that nitrate forcing could
increase to -1.28 W/m(2) by 2100, while sulfate forcing declines to
-0.85 W/m(2). This result shows that future estimates of aerosol
forcing based solely on predicted sulfate concentrations may be
misleading and that the potential for significant concentrations of
ammonium nitrate needs to be considered in estimates of future
climate change. Calculated direct aerosol forcing is highly
sensitive to the model treatment of water uptake. By calculating
the equilibrium water content of a SO42--NH4+ aerosol mixture and
the optical properties of the wet aerosol, we estimate a forcing
that is almost 35% greater than that derived from correcting a low
relative humidity scattering coefficient with an empirical f(RH)
factor. The discrepancy stems from the failure of the empirical
parameterization to adequately account for water uptake above about
90% relative humidity. These results suggest that water uptake
above 90% RH may make a substantial contribution to average direct
forcing, although subgrid-scale variability makes it difficult to
represent humid areas in a GCM.
C1 CALTECH, Dept Chem, Pasadena, CA 91125 USA.
NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Harvard
Univ, Div Engn & Appl Sci, Cambridge, MA 02138 USA.},
 bibtype = {article},
 author = {Adams, P J and Seinfeld, J H and Koch, D and Mickley, L and Jacob, D},
 journal = {J. Geophys. Res.-Atmos.}
}

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