INVESTIGADORES
VERA Carolina Susana
artículos
Título:
Cold Season Synoptic-Scale Waves over Subtropical South America
Autor/es:
VERA, CAROLINA; VIGLIRAROLO, PAULA; BERBERY, E. H.
Revista:
MONTHLY ENERGY REVIEW
Editorial:
AMER METEOROLOGICAL SOC
Referencias:
Lugar: Boston; Año: 2002 vol. 130 p. 684 - 699
ISSN:
0027-0644
Resumen:
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 (;308S) and over the subpolar jet latitudes (;608S). 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 threedimensional
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 occurrence 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.