Influence of South America orography on summertime precipitation in Southeastern South America. Climate Dynamics

JUNQUAS, C.; LI. L; VERA. C; LE TREUT, H.; K. TAKAHASHI

CLIMATE DYNAMICS

SPRINGER

Lugar: Berlin; Año: 2016 vol. 46 p. 3941 - 3963

0930-7575

Impacts of the main South American orographicstructures (the Andes, the Brazilian Plateau and the Guianashield) on the regional climate and associated global teleconnectionare investigated through numerical experimentsin which some of these features are suppressed.Simulations are performed with a ??two-way nesting?? systemcoupling interactively the regional and global versionsof the LMDZ4 atmospheric general circulation model. Atregional scale, the simulations confirm previous studies,showing that both the Andes and the Brazilian Plateau exerta control on the position and strength of the South Atlanticconvergence zone (SACZ), mainly through their impact onthe low-level jet and the coastal branch of the subtropicalanticyclones. The northern topography of South Americaappears to be crucial to determine the leading mode of rainfallvariability in eastern South America, which manifestsitself as a dipole-like pattern between Southeastern SouthAmerica and the SACZ region. The suppression of SouthAmerica orography also shows global-scale effects, correspondingto an adjustment of the global circulation system.Changes in atmospheric circulation and precipitation arefound in remote areas on the globe, being the consequencesof various teleconnection mechanisms. When the Brazilian Plateau and the Andes are suppressed, there is a decrease ofprecipitation in the SACZ region, associated with a weakeningof the large-scale ascendance. Changes are describedin terms of anomalies in the Walker circulation, meridionaldisplacements of the mid-latitude jet stream, Southernannular mode anomalies and modifications of Rossby wavetrain teleconnection processes.