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| Titel |
The Empirical Forcing Function as a tool for the diagnosis of large-scale atmospheric anomalies |
| VerfasserIn |
C. Andrade, J. A. Santos, J. G. Pinto, J. Corte-Real, S. Leite |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 28, no. 1 ; Nr. 28, no. 1 (2010-01-15), S.75-87 |
| Datensatznummer |
250016744
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| Publikation (Nr.) |
 copernicus.org/angeo-28-75-2010.pdf |
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| Zusammenfassung |
| The time-mean quasi-geostrophic potential vorticity equation of the
atmospheric flow on isobaric surfaces can explicitly include an atmospheric
(internal) forcing term of the stationary-eddy flow. In fact, neglecting some
non-linear terms in this equation, this forcing can be mathematically
expressed as a single function, called Empirical Forcing Function (EFF),
which is equal to the material derivative of the time-mean potential
vorticity. Furthermore, the EFF can be decomposed as a sum of seven
components, each one representing a forcing mechanism of different nature.
These mechanisms include diabatic components associated with the radiative
forcing, latent heat release and frictional dissipation, and components
related to transient eddy transports of heat and momentum. All these factors
quantify the role of the transient eddies in forcing the atmospheric
circulation. In order to assess the relevance of the EFF in diagnosing
large-scale anomalies in the atmospheric circulation, the relationship
between the EFF and the occurrence of strong North Atlantic ridges over the
Eastern North Atlantic is analyzed, which are often precursors of severe
droughts over Western Iberia. For such events, the EFF pattern depicts a
clear dipolar structure over the North Atlantic; cyclonic (anticyclonic)
forcing of potential vorticity is found upstream (downstream) of the
anomalously strong ridges. Results also show that the most significant
components are related to the diabatic processes. Lastly, these results
highlight the relevance of the EFF in diagnosing large-scale anomalies, also
providing some insight into their interaction with different physical
mechanisms. |
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