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| Titel |
Uncertainty in modeling dust mass balance and radiative forcing from size parameterization |
| VerfasserIn |
C. Zhao, S. Chen, L. R. Leung, Y. Qian, J. F. Kok, R. A. Zaveri, J. Huang |
| 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 ; 13, no. 21 ; Nr. 13, no. 21 (2013-11-05), S.10733-10753 |
| Datensatznummer |
250085790
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| Publikation (Nr.) |
 copernicus.org/acp-13-10733-2013.pdf |
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| Zusammenfassung |
This study examines the uncertainties in simulating mass balance and
radiative forcing of mineral dust due to biases in the dust size
parameterization. Simulations are conducted quasi-globally
(180° W–180° E and 60° S–70° N) using the WRF-Chem model with three different approaches to represent dust
size distribution (8-bin, 4-bin, and 3-mode). The biases in the 3-mode or
4-bin approaches against a relatively more accurate 8-bin approach in
simulating dust mass balance and radiative forcing are identified. Compared
to the 8-bin approach, the 4-bin approach simulates similar but coarser size
distributions of dust particles in the atmosphere, while the 3-mode approach
retains more fine dust particles but fewer coarse dust particles due to its
prescribed σg of each mode. Although the 3-mode approach yields up
to 10 days of longer dust mass lifetime over the remote oceanic regions than
the 8-bin approach, the three size approaches produce a similar dust mass
lifetime (3.2 days to 3.5 days) on quasi-global average, reflecting that the
global dust mass lifetime is mainly determined by the dust mass lifetime near
the dust source regions.
With the same global dust emission (~4600 Tg yr−1), the 8-bin
approach produces a dust mass loading of 39 Tg, while the 4-bin and 3-mode
approaches produce 3% (40.2 Tg) and 25% (49.1 Tg) higher dust
mass loading, respectively. The difference in dust mass loading between the
8-bin approach and the 4-bin or 3-mode approaches has large spatial
variations, with generally smaller relative difference
(<10%) near the surface over the dust source regions. The
three size approaches also result in significantly different dry and wet
deposition fluxes and number concentrations of dust. The difference in dust
aerosol optical depth (AOD) (a factor of 3) among the three size approaches
is much larger than their difference (25%) in dust mass loading.
Compared to the 8-bin approach, the 4-bin approach yields stronger dust
absorptivity, while the 3-mode approach yields weaker dust absorptivity.
Overall, on quasi-global average, the three size parameterizations result in
a significant difference of a factor of 2~3 in dust surface cooling
(−1.02~−2.87 W m−2) and atmospheric warming
(0.39~0.96 W m−2) and in a tremendous difference of a factor of
~10 in dust TOA (top of atmosphere) cooling
(−0.24~−2.20 W m−2). The impact of different size
representations on dust radiative forcing efficiency is smaller. An
uncertainty of a factor of 2 is quantified in dust emission estimation due to
the different size parameterizations. This study also highlights the
uncertainties in modeling dust mass and number loading, deposition fluxes,
and radiative forcing resulting from different size parameterizations, and
motivates further investigation of the impact of size parameterizations on
modeling dust impacts on air quality, climate, and ecosystems. |
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