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| Titel |
Radiative impact of mineral dust on monsoon precipitation variability over West Africa |
| VerfasserIn |
C. Zhao, X. Liu, L. Ruby Leung, S. Hagos |
| 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 ; 11, no. 5 ; Nr. 11, no. 5 (2011-03-01), S.1879-1893 |
| Datensatznummer |
250009436
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| Publikation (Nr.) |
 copernicus.org/acp-11-1879-2011.pdf |
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| Zusammenfassung |
| The radiative forcing of dust and its impact on
precipitation over the West Africa monsoon (WAM) region is simulated using a
coupled meteorology and aerosol/chemistry model (WRF-Chem). During the
monsoon season, dust is a dominant contributor to aerosol optical depth
(AOD) over West Africa. In the control simulation, on 24-h domain
average, dust has a cooling effect (−6.11 W m−2) at the surface, a
warming effect (6.94 W m−2) in the atmosphere, and a relatively small
TOA forcing (0.83 W m−2). Dust modifies the surface energy budget and
atmospheric diabatic heating. As a result, atmospheric stability is
increased in the daytime and reduced in the nighttime, leading to a
reduction of late afternoon precipitation by up to 0.14 mm/h (25%) and
an increase of nocturnal and early morning precipitation by up to 0.04 mm/h
(45%) over the WAM region. Dust-induced reduction of diurnal
precipitation variation improves the simulated diurnal cycle of
precipitation when compared to measurements. However, daily precipitation is
only changed by a relatively small amount (−0.17 mm/day or −4%). The
dust-induced change of WAM precipitation is not sensitive to interannual
monsoon variability. On the other hand, sensitivity simulations with weaker
to stronger absorbing dust (in order to represent the uncertainty in dust
solar absorptivity) show that, at the lower atmosphere, dust longwave
warming effect in the nighttime surpasses its shortwave cooling effect in
the daytime; this leads to a less stable atmosphere associated with more
convective precipitation in the nighttime. As a result, the dust-induced
change of daily WAM precipitation varies from a significant reduction of
−0.52 mm/day (−12%, weaker absorbing dust) to a small increase of
0.03 mm/day (1%, stronger absorbing dust). This variation originates from the
competition between dust impact on daytime and nighttime precipitation,
which depends on dust shortwave absorption. Dust reduces the diurnal
variation of precipitation regardless of its absorptivity, but more
reduction is associated with stronger absorbing dust. |
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