Relations of South American summer rainfall interannual variations with the Pacific Decadal Oscillation

摘要

The anomaly patterns of rainfall in South America for El Nino/Southern Oscillation (ENSO) extreme conditions stratified according to the high, low, and normal Pacific (inter-) Decadal Oscillation (PDO) phases (HPDO, LPDO and NPDO) are examined for the three bi-months of the season from November to April. El Nino (EN) and La Nina (LN) composites as well as the linear (EN - LN) and nonlinear (EN + LN) components of the precipitation anomaly patterns relative to ENSO show substantial differences among the three PDO phases. The differences in the strength of ENSO teleconnections for the South American rainfall might be related to the PDO, which creates a background for these teleconnections acting constructively (destructively) when ENSO and PDO are in the same (opposite) phase. An interesting aspect is the occurrence of robust structures of the nonlinear component, which are due to the same sign rainfall anomalies for EN and LN composites. This is particularly conspicuous for the HPDO over eastern Brazil in the South Atlantic Convergence Zone (SACZ) region during Nov/Dec and Jan/Feb, for the HPDO over northernorthwestern South America during Mar/Apr, and for the NPDO over northeastern Brazil during Mar/Apr. The results presented here might have relevant implications for climate monitoring purposes. Copyright (c) 2006 Royal Meteorological Society.