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| Titel |
Impacts of increasing the aerosol complexity in the Met Office global numerical weather prediction model |
| VerfasserIn |
J. P. Mulcahy, D. N. Walters, N. Bellouin, S. F. Milton |
| 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 ; 14, no. 9 ; Nr. 14, no. 9 (2014-05-13), S.4749-4778 |
| Datensatznummer |
250118699
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| Publikation (Nr.) |
 copernicus.org/acp-14-4749-2014.pdf |
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| Zusammenfassung |
| The inclusion of the direct and indirect radiative effects of aerosols in high-resolution
global numerical weather prediction (NWP) models is being
increasingly recognised as important for the improved accuracy of short-range
weather forecasts. In this study the impacts of increasing the aerosol
complexity in the global NWP configuration of the Met Office Unified Model
(MetUM) are investigated. A hierarchy of aerosol representations are
evaluated including three-dimensional monthly mean speciated aerosol
climatologies, fully prognostic aerosols modelled using the CLASSIC aerosol
scheme and finally, initialised aerosols using assimilated aerosol fields
from the GEMS project. The prognostic aerosol schemes are better able to
predict the temporal and spatial variation of atmospheric aerosol optical
depth, which is particularly important in cases of large sporadic aerosol
events such as large dust storms or forest fires. Including the direct effect
of aerosols improves model biases in outgoing long-wave radiation over West
Africa due to a better representation of dust. However, uncertainties in dust
optical properties propagate to its direct effect and the subsequent model
response. Inclusion of the indirect aerosol effects improves surface
radiation biases at the North Slope of Alaska ARM site due to lower cloud
amounts in high-latitude clean-air regions. This leads to improved
temperature and height forecasts in this region. Impacts on the global mean
model precipitation and large-scale circulation fields were found to be
generally small in the short-range forecasts. However, the indirect aerosol
effect leads to a strengthening of the low-level monsoon flow over the
Arabian Sea and Bay of Bengal and an increase in precipitation over Southeast
Asia. Regional impacts on the African Easterly Jet (AEJ) are also presented
with the large dust loading in the aerosol climatology enhancing of the heat
low over West Africa and weakening the AEJ. This study highlights the
importance of including a more realistic treatment of aerosol–cloud
interactions in global NWP models and the potential for improved global
environmental prediction systems through the incorporation of more complex
aerosol schemes. |
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