CMIP6 projections of the South American Monsoon Lifecycle: comparison with pre and post statistical downscaling

Abstract

The climate of a great part of South America presents two well-defined seasons: one dry, in general, from April to September, and another wet, from October to March, which characterizes a monsoon regime. As most of the energy generation in this monsoon region is hydroelectric, precipitation is a target of several studies. In this context, the South America Monsoon (SAM) lifecycle (onset, demise, and duration) in projections of eight global climate models (GCMs) of the Coupled Model Intercomparison Project Phase 6 (CMIP6) is analyzed in this study using two approaches: (a) the original GCM outputs downloaded from the Earth System Grid Federation (ESGF) and (b) after application of the statistical downscaling (SD) technique. Daily precipitation data from the Climate Prediction Center (CPC), with a horizontal resolution of 0.5o, are used as a reference. So, the final resolution of the GCMs after applying the Quantile Delta Mapping (QDM) is the same as CPC. SAM lifecycle is identified with a similar methodology from Liebman and Marengo published in 2001, which is based on the accumulated daily precipitation anomalies. The rainy season is considered to be the period during which precipitation exceeds its climatological annual average, then a positive slope indicates the rainy season. Note that this methodology is proper to be applied in projections because it does not assume any threshold. Initial results indicate a shorter lifetime of SAM at the end of the century.  The authors thank the Programa de P&D regulado pela ANEEL: empresa Engie Brasil Energia e Companhia Energética Estreito, MC&E, FAPEMIG, CAPES and CNPq for the financial support.