| Summary: | The Southern Hemisphere (SH) climate and weather is affected by several modes of variability and climate phenomena of different time and spatial scales. In addition to these, atmospheric Rossby waves are another component of the SH atmosphere dynamics with major influence on weather. In both hemispheres, quasi-stationary Rossby waves attract particular interest as they are often associated with synoptic scale extreme weather events. In the SH, the most prominent quasi-stationary Rossby wave pattern in the extratropical circulation is the zonal wavenumber 3 (ZW3), with maximum amplitude around 55°S. It is well documented that this pattern has strong impacts on meridional heat and momentum transport in mid to high-latitudes, and on Antarctic sea-ice extent. However, little is known about its impacts at its northern flank. In this work, we study the impact of ZW3 on temperature and precipitation across the SH, with special emphasis on some of the most densely populated regions in South America. Using ERA5 data, we examine the lifecycle of its regional effect and juxtapose it with the zonally symmetric Southern Annular Mode (SAM).
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