Artículo de revista
Cold Air Incursions over Subtropical South America: Mean Structure and Dynamics
Fecha
2000Autor
Garreaud Salazar, René
Institución
Resumen
Synoptic-scale incursions of midlatitude air moving into subtropical South America (to the east of the Andes
Cordillera) are observed to occur year-round with a periodicity of about 1–2 weeks. During wintertime, they
have a profound impact upon the low-level temperature field, and extreme episodes produce freezing conditions
from central Argentina to southern Brazil and Bolivia. Warm season episodes produce less dramatic variations
of temperature, but they organize deep convection in the form of synoptic-scale bands of convective cloudiness
along the leading edge of the cool air. On the basis of 17 yr of NCEP–NCAR reanalysis and outgoing longwave
radiation fields, the mean, synoptic-scale structure, and evolution of these incursions is documented, using a
simple compositing technique. The underlying physical mechanisms responsible for the occurrence of these
incursions are also investigated by diagnosing the leading dynamic and thermodynamic forcing of their development.