The Chaco Low (CHL) is a typical feature of the rainy season and an important component of the South American Monsoon System. In this work we describe several aspects of the Chaco Low do not define yet, including its lifecycle and associated processes, as well as its role on the continental-scale circulation. The study focuses on the summer months using the ETA-CPTEC reanalysis (2000-2004). A composite of "high" and "low" CHL stages was performed using three monthly cases of maximum and minimum surface pressure at 22°S-60°W. The CHL lifecycle is related with the passage of a frontal-like disturbance of synoptic scale (or larger) affecting the lower troposphere, and occurs in concert with strong anomalies of temperature, wind and moisture over tropical/subtropical South America. There is also a clear connection between the CHL and other regional systems such as the South Atlantic Convergence Zone, the Northwestern Argentinean Low and the Low Level Jet. The deepening of the low is related with the occurrence of convective precipitation and clear skies, while the weakening of the low is mainly due to post frontal cold advection.
Chaco Low; lifecycle; thermal low
