IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Changes in the Hadley cell descending branch and its impact on long-term precipitation variability in southwestern South America
Autor/es:
ELIZABETH NARANJO TAMAYO; MAXIMILIANO VIALE; MYRIAM KHODRI; VALERIE DAUX; JUAN ANTONIO RIVERA; JULIÁN VILLAMAYOR; GABRIEL ARNOULD
Lugar:
San Francisco
Reunión:
Conferencia; AGU Fall Meeting 2019; 2019
Institución organizadora:
American Geophysical Union
Resumen:
The climate and its variability along the Cordillera de Los Andes, from the subtropics to latitudes around 45°S, are influenced by different large-scale atmospheric and oceanic forcings, which have been documented mainly in variables such as temperature and precipitation. For instance, a centennial decreasing trend has been observed in precipitation records estimated from tree ring widths from the Altiplano area to northern Patagonia. These declining trends in precipitation were associated to an increase in the frequency of droughts, fostering the occurrence of a mega-drought along the Central Andes (between 30° and 40°S). In this region, the climate is strongly affected by the descending branch of the Hadley circulation. This global circulation plays a key role in determining the location of the subtropical dry zones, which are important not only for the hydrological cycles but also for the global energy budget of the Earth?s climate system. Recent studies suggest that the Hadley circulation is expanding poleward approximately 0.2° per decade in each hemisphere since 1979. However, limited evidences and high uncertainties exist when considering longer time periods and about its impacts on precipitation changes in the subtropics.The purpose of this investigation is to study the long-term changes in the position of the descending branch of the Hadley cell surrounding South America, by describing the changes in the semi-permanent Southeastern Pacific High (SPH) position. Reanalysis and observations during the 20th century and the first part of the 21st century were used to calculate metrics that quantify movement in the poleward boundary of the Hadley cell and its impacts on precipitation. Monthly time series of meridional stream function (ψ500) and the latitude of maximum sea level pressure (SLP) over the Southeastern Pacific Ocean were considered, as well as some indices for describing the SPH intensity, SPH latitude and SPH longitude. Based on precipitation records between 25° and 45°S, the links between the observed trends in precipitation and the changes in the Hadley cell were explored, and results will be discussed in this presentation.