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| Titel |
Temperature decrease in the extratropics of South America in response to a tropical forcing during the austral winter |
| VerfasserIn |
G. V. Müller |
| 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 (2010-01-08), S.1-9 |
| Datensatznummer |
250016737
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1-2010.pdf |
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| Zusammenfassung |
This paper focuses on the dynamic mechanisms that create favorable
conditions for the occurrence of frosts that affect large areas of Argentina
and are denominated generalized frosts (GF). The hemispheric teleconnection
patterns linked to extreme cold events affecting central and northeastern
Argentina during winter are identified. The objective is to determine
whether the conditions found in previous studies for the composite of
winters with extreme (maximum and minimum) frequency of GF occurrence
respond to typical characteristics of the austral winter or they are
inherent to those particular winters. Taking the mean winter as basic state
in the 1961–1990 period, a series of numerical experiments are run using a
primitive equation model in which waves are excited with a thermal forcing.
The positions of the thermal forcing are chosen according to observed
convection anomalies in a basic state given by the austral winters with
extreme frequency of GF occurrence.
The wave trains excited by anomalous convection situated in specific regions
may propagate across the Pacific Ocean and reach South America with the
appropriate phase, creating the local favorable conditions for the
occurrence of GF. However, the anomalous convection is, by itself, not
sufficient since the response also depends on the basic state configuration.
This is proved by placing the forcing over the region of significant
anomalous convection for maximum and minimum frequency of GF occurrence and
the response was very different in comparison to the mean winter. It is
concluded that the conditions for a greater GF frequency of occurrence are
inherent to these particular winters, so that such conditions are not
present in the average winter. |
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