Uncertainties in Projected Rainfall over Brazil: The Role of Climate Model, Bias Correction and Emission Scenario

Abstract Study region Twenty-six rainfall gauge stations distributed over Brazil Study focus The aim of this study is to answer four main questions: How well the Eta regional climate model simulates past precipitation over Brazil? What is the impact of bias correction on the reduction of model’s biases? What is the contribution of climate models, bias correction and emission scenarios to the total uncertainty of projected precipitation? And finally, what is the projected change in precipitation over Brazil? New hydrological insights for the region The performance of raw simulations of the Eta regional climate models vary spatially over Brazil, being the Amazon and North region the regions with the highest biases. However, while the model fails in accuracy, it represents well the annual cycle of the precipitation and the signal of the future changes is robust (that is, it agrees with the signal of the changes after the bias correction and the models agree with each other). The bias correction presented a great impact in the bias reduction. Greater uncertainty levels are attributed to the bias correction followed by the climate models and interaction between climate model and bias correction. The emission scenario is the less contributor to the total uncertainty. Projected precipitation changes indicated a decrease in the daily precipitation and extreme precipitation in the Amazon and North Brazil and increase in the daily precipitation in Southern. The precipitation in winter is expected to increase. Under the IPCC scenario RCP 8.5, homogeneoulsly drier conditions are projected for the entire country.