Changes in summer precipitation variability in central Brazil over the past eight decades

Abstract

AbstractCentral Brazil hydroclimate is in the core region of the South American monsoon system. Thus, understanding precipitation variability in this area is crucial not only for the prediction of extreme events such as droughts and floods, but also for water resources management. Ocean teleconnections influence central Brazil precipitation from intraseasonal to interdecadal frequencies, in both linear and nonlinear ways, mainly during the austral summer. Pacific Ocean climate modes can influence South American precipitation, but how its variability changes over time is still a theme of scientific debate. Here we examined the influence of Pacific variability on summer precipitation in central Brazil during the last eight decades. We applied nonparametric spectral methods to four different observational datasets, and to AMIP‐type precipitation outputs from the Laboratoire de Météorologie Dynamique zoom model (LMDZ) in Coupled Model Intercomparison Project phases 5 and 6 (CMIP5 and CMIP6) contributions of the Institut Pierre Simon Laplace (IPSL) coupled model. Our results showed an increase in amplitude and frequency of summer precipitation variability after the 1970s climate transition. Spectral analysis associated these changes to a transition in Pacific Ocean influence to central Brazil precipitation, from PDO‐ to El Niño–Southern Oscillation (ENSO)‐related variability after the 1970s climate transition. Composite analysis suggests these changes are related to teleconnection patterns between the Pacific Ocean and South America precipitation.