Summertime Incursions of Midlatitude Air into Subtropical and Tropical South America

摘要: Abstract Transient incursions of midlatitude air to the east Andes Mountains into subtropical and tropical latitudes are a distinctive feature synoptic climatology over South America. The mean synoptic-scale structure these is documented in this paper on basis compositing analysis NCEP–NCAR reanalyzed meteorological fields satellite-based outgoing longwave radiation measurements. Although year-round phenomenon, with relatively modest seasonal changes their structure, focused austral summer, when they have largest impact precipitation field. summertime move equatorward at speed 10 m s−1 retain identities intervals about 5 days. upper-level circulation characterized by trough–ridge couplet that provides quasigeostrophic forcing system. Before onset air, approaching trough tend...