Cold season synoptic-scale waves over subtropical South America
The most active winter synoptic-scale wave patterns over South America are identified using an extended empirical orthogonal function (EEOF) technique and are physically diagnosed using composite methods. Results show that the leading modes of short timescale variability propagate along two main pat...
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2002
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00270644_v130_n3_p684_Vera http://hdl.handle.net/20.500.12110/paper_00270644_v130_n3_p684_Vera |
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paper:paper_00270644_v130_n3_p684_Vera2025-07-30T17:35:52Z Cold season synoptic-scale waves over subtropical South America Heat flux Moisture Perturbation techniques Precipitation (meteorology) Storms Waves Baroclinic growth Weather forecasting baroclinic wave cyclone jet flow orography synoptic meteorology South America The most active winter synoptic-scale wave patterns over South America are identified using an extended empirical orthogonal function (EEOF) technique and are physically diagnosed using composite methods. Results show that the leading modes of short timescale variability propagate along two main paths: over the subtropical jet latitudes (~30°S) and over the subpolar jet latitudes (~60°S). This research focuses on the subtropical mode and its evolution over South America. The observed structure of the systems associated with the subtropical mode resembles that of midlatitude baroclinic waves. Both cyclonic and anticyclonic perturbations display significant modifications in their three-dimensional structure as they evolve over extratropical and subtropical South America. While the upper-level perturbations are mostly unaffected when moving eastward, the lower-level perturbations advance following the shape of the Andes Mountains and exhibit an abrupt equatorward migration at the lee side of the mountains. As a result of such detachment, smaller eddy heat fluxes are observed in the vicinity of the orography and consequently a weaker eddy baroclinic growth is observed. Once the upper-level system is on the lee side, the perturbations acquire a more typical baroclinic wave structure and low-level intensification of the system occurs. The latter is largest around 1000 km east of the orography, where enhanced moisture transports from tropical latitudes along the eastern portion of the low-level cyclone favor precipitation occurence over southeastern South America. Those precipitation processes seem to provide a diabatic source of energy that further contributes to the strengthening of the low-level cyclone. In addition, an intensification of the cyclone once over the ocean was found in 60% of the situations considered, which is consistent with previous research suggesting an additional source of moisture and heat flux due to the warm waters of the Brazil Current. 2002 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00270644_v130_n3_p684_Vera http://hdl.handle.net/20.500.12110/paper_00270644_v130_n3_p684_Vera |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Heat flux Moisture Perturbation techniques Precipitation (meteorology) Storms Waves Baroclinic growth Weather forecasting baroclinic wave cyclone jet flow orography synoptic meteorology South America |
| spellingShingle |
Heat flux Moisture Perturbation techniques Precipitation (meteorology) Storms Waves Baroclinic growth Weather forecasting baroclinic wave cyclone jet flow orography synoptic meteorology South America Cold season synoptic-scale waves over subtropical South America |
| topic_facet |
Heat flux Moisture Perturbation techniques Precipitation (meteorology) Storms Waves Baroclinic growth Weather forecasting baroclinic wave cyclone jet flow orography synoptic meteorology South America |
| description |
The most active winter synoptic-scale wave patterns over South America are identified using an extended empirical orthogonal function (EEOF) technique and are physically diagnosed using composite methods. Results show that the leading modes of short timescale variability propagate along two main paths: over the subtropical jet latitudes (~30°S) and over the subpolar jet latitudes (~60°S). This research focuses on the subtropical mode and its evolution over South America. The observed structure of the systems associated with the subtropical mode resembles that of midlatitude baroclinic waves. Both cyclonic and anticyclonic perturbations display significant modifications in their three-dimensional structure as they evolve over extratropical and subtropical South America. While the upper-level perturbations are mostly unaffected when moving eastward, the lower-level perturbations advance following the shape of the Andes Mountains and exhibit an abrupt equatorward migration at the lee side of the mountains. As a result of such detachment, smaller eddy heat fluxes are observed in the vicinity of the orography and consequently a weaker eddy baroclinic growth is observed. Once the upper-level system is on the lee side, the perturbations acquire a more typical baroclinic wave structure and low-level intensification of the system occurs. The latter is largest around 1000 km east of the orography, where enhanced moisture transports from tropical latitudes along the eastern portion of the low-level cyclone favor precipitation occurence over southeastern South America. Those precipitation processes seem to provide a diabatic source of energy that further contributes to the strengthening of the low-level cyclone. In addition, an intensification of the cyclone once over the ocean was found in 60% of the situations considered, which is consistent with previous research suggesting an additional source of moisture and heat flux due to the warm waters of the Brazil Current. |
| title |
Cold season synoptic-scale waves over subtropical South America |
| title_short |
Cold season synoptic-scale waves over subtropical South America |
| title_full |
Cold season synoptic-scale waves over subtropical South America |
| title_fullStr |
Cold season synoptic-scale waves over subtropical South America |
| title_full_unstemmed |
Cold season synoptic-scale waves over subtropical South America |
| title_sort |
cold season synoptic-scale waves over subtropical south america |
| publishDate |
2002 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00270644_v130_n3_p684_Vera http://hdl.handle.net/20.500.12110/paper_00270644_v130_n3_p684_Vera |
| _version_ |
1840324094881431552 |