South American Cold Surges: Types, Composites, and Case Studies
| Autor: | David J. Knight, Joseph J. Nocera, Lance F. Bosart, Eric G. Hoffman, Anthony R. Lupo |
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| Rok vydání: | 2001 |
| Předmět: | |
| Zdroj: | Monthly Weather Review. 129:1021-1041 |
| ISSN: | 1520-0493 0027-0644 |
| DOI: | 10.1175/1520-0493(2001)129<1021:sacstc>2.0.co;2 |
| Popis: | This paper examines the climatological, large-scale, and synoptic-scale aspects of South American cold surges using NCEP–NCAR gridded reanalyses for the 1992–96 period. Three common cold surge types are identified on the basis of a thickness (1000–850 hPa) criteria: type 1—a transient surge associated with weak anticyclone development east of the Andes in the absence of ridging aloft, type 2—a strong and persistent surge associated with dynamic anticyclogenesis aloft and strong surface anticyclone development east of the Andes, and type 3—a surge east of the Brazilian coastal mountains. Cold surges are most common during the winter and spring (Jun–Nov), accounting for 189 of the 256 events (74%). Case studies of two events (19–22 Jul 1992 and 12–14 Apr 1993) are conducted from both a conventional isobaric and a potential vorticity (PV) perspective. The upper-air flow pattern in the July 1992 type 2 case is characterized by the presence of a strong ridge–trough couplet, which amplifies and becomes... |
| Databáze: | OpenAIRE |
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