Using dynamical downscaling of climate projections for the assessment of climate change impacts on precipitation over Paraná and Paraguay river basins

Paraná River basin is one of the most important river basins for the energy sector in Brazil and, together with Paraguay River basin, forms part of the La Plata basin, which is the second largest river basin in South America. An evaluation of precipitation over Paraná and Paraguay River basins during the 21st century is performed using climate models to assess changes in the water cycle. In addition to precipitation, this study uses a global reanalysis in the evaluation of the ability of three global climate models to represent the climatological patterns of South American summer circulation that impact the hydrological cycle of the two river basins. The climate integrations used in this study are available for the historical period, 1975-2004, and for the projections, 2041-2070 and 2071- 2100. The Representative Concentration Pathway (RCP) 8.5, which is the most extreme RCP from the Fifth Phase of the Coupled Model Intercomparison Project, forced the climate projections used in this study. The regionalization was performed using RegCM4 under the Coordinated Regional Downscaling Experiment project, which allows for more detailed analyzes in the basins. RegCM4 used initial and boundary conditions from the following global models, also analyzed in this study: The Geophysical Fluid Dynamics Laboratory's ESM2M; the Max Planck Institute's ESM-MR; and HadGEM2 from the Hadley Center. For the historical period, the performance of HadGEM2 and ESM2M agree better with the global reanalysis in the representation of South American atmospheric patterns than ESM-MR. RegCM4 driven by HadGEM2 shows smaller errors in precipitation compared to the gauge-based products in the basins. Regarding the future climate, small changes in precipitation minus evaporation occur in January, except for RegCM4 driven by ESM-MR in the southwestern Paraná River basin. (author)