Seasonal dependence of surface-atnosphere interctions for subtropical South America

ESTELA A. COLLINI ¹, ERNESTO H. BERBERY ², VICENTE BARROS³

Foz de Iguazú

Congreso; I8th International Conference on Southern Hemisphere Meteorology and Oceanography.; 2006

American Meteorological Society

Different studies have shown the relationship between the Low Level Jet (LLJ), the moisture transport and the precipitation in subtropical South America. Due to the relevance of these links for the region’s climate, a field experiment, the South American Low-level Jet Field  Experiment (SALLJEX) was carried out in the austral summer of 2002/2003 (Paegle et al., at http://www.met.utah.edu/jnpaegle/research/ALLS.html ). Simulations with the Eta model have suggested that the South American LLJ can be stronger than the Great Plains LLJ in North America (Berbery and Collini 2000). Of relevance for the present study is the fact that the SALLJ is observed throughout the year, although revealing differences in location and strength (Berbery and Barros 2002). The present work seeks to identify the role of soil moisture anomalies on the seasonal characteristics and the interannual variability of the atmospheric component of the hydrological cycle over subtropical South America. The objective is to investigate the feedbacks between soil moisture and precipitation over the South American Monsoon area during the El Niño- Southern Oscillation (ENSO) cycle 1982-83. To this end, simulations were performed with the regional mesoscale Eta model (Mesinger 1997; Mesinger et al. 1988; Black, 1994), using the NCEP/NCAR Reanalysis (Kalnay et al., 1996) as initial and boundary conditions. The sensitivity experiments of the model response to soil moisture changes involve the same initial field and boundary conditions but increasing or decreasing the values of the soil moisture field covering the entire model domain. For this study, ENSO cycle were chosen. http://www.met.utah.edu/jnpaegle/research/ALLS.html ). Simulations with the Eta model have suggested that the South American LLJ can be stronger than the Great Plains LLJ in North America (Berbery and Collini 2000). Of relevance for the present study is the fact that the SALLJ is observed throughout the year, although revealing differences in location and strength (Berbery and Barros 2002). The present work seeks to identify the role of soil moisture anomalies on the seasonal characteristics and the interannual variability of the atmospheric component of the hydrological cycle over subtropical South America. The objective is to investigate the feedbacks between soil moisture and precipitation over the South American Monsoon area during the El Niño- Southern Oscillation (ENSO) cycle 1982-83. To this end, simulations were performed with the regional mesoscale Eta model (Mesinger 1997; Mesinger et al. 1988; Black, 1994), using the NCEP/NCAR Reanalysis (Kalnay et al., 1996) as initial and boundary conditions. The sensitivity experiments of the model response to soil moisture changes involve the same initial field and boundary conditions but increasing or decreasing the values of the soil moisture field covering the entire model domain. For this study, ENSO cycle were chosen.