The Chaco Low and the Northwestern Argentinean Low are frequently confounded or treated as a single system, due to our limited knowledge about them (especially concerning the Chaco Low), the low resolution of global analyses -that show them as a single low pressure system-, and the relatively poor data coverage over the region where they are usually located. This article aims to contribute to a better understanding of the differences and similarities between them, as well as to analyze the atmospheric dynamical and thermo-dynamical conditions where they evolve. It is considered that this study will aid to a better recognition of both systems. With this purpose, regional reanalyses from the Eta/CPTEC model for the 2000-2004 period has been used. The article focuses in summer months, since both low-pressure systems are more active during this season. Results show that the Northwestern Argentinean Low is more related to transient activity, as can be deducted from the subtropical jet influence on this system and also from the temporal variability of some key variables -such as the sea level pressure and the equivalent potential temperature-. From a thermo-dynamic point of view, the Chaco Low develops in a more unstable environment and is less influenced by middle latitude dynamics.
Thermal low; synoptic climatology; thermo-dynamical structure
