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| Titel |
Effects of the physical state of tropospheric ammonium-sulfate-nitrate particles on global aerosol direct radiative forcing |
| VerfasserIn |
S. T. Martin, H.-M. Hung, R. J. Park, D. J. Jacob, R. J. D. Spurr, K. V. Chance, M. Chin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 1 ; Nr. 4, no. 1 (2004-02-04), S.183-214 |
| Datensatznummer |
250001488
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| Publikation (Nr.) |
 copernicus.org/acp-4-183-2004.pdf |
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| Zusammenfassung |
| The effect of aqueous versus crystalline sulfate-nitrate-ammonium tropospheric particles
on global aerosol direct radiative forcing is assessed. A global three-dimensional chemical
transport model predicts sulfate, nitrate, and ammonium aerosol mass. An aerosol
thermodynamics model is called twice, once for the upper side (US) and once for lower side (LS)
of the hysteresis loop of particle phase. On the LS, the sulfate mass budget is
40% solid ammonium sulfate, 12% letovicite, 11% ammonium bisulfate, and
37% aqueous. The LS nitrate mass budget is 26% solid ammonium nitrate, 7% aqueous, and
67% gas-phase nitric acid release due to increased volatility upon crystallization. The LS ammonium budget is
45% solid ammonium sulfate, 10% letovicite, 6% ammonium bisulfate, 4% ammonium nitrate,
7% ammonia release due to increased volatility, and 28% aqueous. LS aerosol water mass partitions
as 22% effloresced to the gas-phase and 78% remaining as aerosol mass. The predicted US/LS
global fields of aerosol mass are employed in a Mie scattering model to generate
global US/LS aerosol optical properties, including scattering efficiency, single scattering
albedo, and asymmetry parameter. Global annual average LS optical depth and mass scattering efficiency
are, respectively, 0.023 and 10.7 m2 (g SO4-2)-1, which compare to US values of 0.030 and
13.9 m2 (g SO4-2)-1. Radiative transport is computed, first for a base case having no aerosol and then for the
two global fields corresponding to the US and LS of the hysteresis loop. Regional, global,
seasonal, and annual averages of top-of-the-atmosphere aerosol radiative forcing on the LS and
US (FL and FU, respectively, in W m-2) are calculated. Including both anthropogenic and natural
emissions, we obtain global annual averages of FL=-0.750,
FU=-0.930, and DFU,L=24% for
full sky calculations without clouds and FL=-0.485, FU=-0.605, and
DFU,L=25% when clouds
are included. Regionally, DFU,L=48% over the USA,
55% over Europe, and 34% over East Asia. Seasonally, DFU,L
varies from 18% in DJF to 75% in SON over the USA. The global annual average contribution from anthropogenic aerosol is
FL=-0.314 and FU=-0.404, which yield normalized direct radiative forcings
(G) of GL=-205 W (g SO4-2)-1
and GU=-264 W (g
SO4-2)-1. |
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