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| Titel |
Consistent response of Indian summer monsoon to Middle East dust in observations and simulations |
| VerfasserIn |
Q. Jin, J. Wei, Z.-L. Yang, B. Pu, 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 ; 15, no. 17 ; Nr. 15, no. 17 (2015-09-02), S.9897-9915 |
| Datensatznummer |
250120013
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| Publikation (Nr.) |
 copernicus.org/acp-15-9897-2015.pdf |
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| Zusammenfassung |
| The response of the Indian summer monsoon (ISM) circulation and precipitation
to Middle East dust aerosols on sub-seasonal timescales is studied using
observations and the Weather Research and Forecasting model coupled with
online chemistry (WRF-Chem). Satellite data show that the ISM rainfall in
coastal southwest India, central and northern India, and Pakistan is closely
associated with the Middle East dust aerosols. The physical mechanism behind
this dust–ISM rainfall connection is examined through ensemble simulations
with and without dust emissions. Each ensemble includes 16 members with
various physical and chemical schemes to consider the model uncertainties in
parameterizing short-wave radiation, the planetary boundary layer, and
aerosol chemical mixing rules. Experiments show that dust aerosols increase
rainfall by about 0.44 mm day−1 (~10 % of the climatology)
in coastal southwest India, central and northern India, and north Pakistan, a
pattern consistent with the observed relationship. The ensemble mean rainfall
response over India shows a much stronger spatial correlation with the
observed rainfall response than any other ensemble members. The largest
modeling uncertainties are from the boundary layer schemes, followed by
short-wave radiation schemes. In WRF-Chem, the dust aerosol optical depth
(AOD) over the Middle East shows the strongest correlation with the ISM
rainfall response when dust AOD leads rainfall response by about 11 days.
Further analyses show that increased ISM rainfall is related to enhanced
southwesterly monsoon flow and moisture transport from the Arabian Sea to the
Indian subcontinent, which are associated with the development of an
anomalous low-pressure system over the Arabian Sea, the southern Arabian
Peninsula, and the Iranian Plateau due to dust-induced heating in the
troposphere. The dust-induced heating in the mid-upper troposphere is mainly
located in the Iranian Plateau rather than the Tibetan Plateau. This study
demonstrates a thermodynamic mechanism that links remote desert dust
emissions in the Middle East to ISM circulation and precipitation variability
on sub-seasonal timescales, which may have implications for ISM rainfall
forecasts. |
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