Dynamic downscaling of climate simulations and projected changes in tropical South America using RegCM4.7

High-resolution (dx = 25 km) simulations of the regional climate model RegCM4.7 coupled with the Community Land Model version 4.5 (CLM4.5) under low (RCP2.6) and high (RCP8.5) emissions scenarios, which interact with the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (AR5-IPCC), were carried out over tropical South America (TSA). These simulations were produced through boundary conditions from simulations driven by the general circulation model HadGEM2-ES. With the goal of verifying the added value (AV) of RegCM4.7, reproducing in an adequate and coherent way the regional aspects of the historical period (1986-2005), as well as evaluating the regional aspects simulated by the model in the scope of the change projections for the far-future (2080-2099). For this study, the climate in the TSA was characterized based on the variables of precipitation and near-surface air temperature. For the evaluation of the spatial-temporal representation, frequency and distribution of the regional and global simulation, the high-resolution observational dataset of the Climate Research Unit version ts4.02 (CRU) was used. Although some differences and biases still persist, RegCM4.7 presents AV in the spatial representation of precipitation and temperature over the northeast region of Brazil and part of the Andes, especially in winter. However, it does not adequately represent precipitation over the Amazon Basin, especially in summer. Results for future projections indicate that the more refined simulation of RegCM4.7 improves the projected change patterns of the coarser resolution simulation of HadGEM2-ES and even modifies the precipitation signal in some cases. Both models project increase temperature with greater magnitude for RCP8.5. RegCM4.7 presents a much more refined and realistic spatial distribution. HadGEM2-ES simulates the major aspects of climate enough to consider forcing RegCM4.7 to generate simulations with better performance and more realistic projections.

Automated summary

High-resolution simulations were conducted using RegCM4.7 and CLM4.5 models to evaluate their performance in simulating historical and future climate change over tropical South America. The results show that RegCM4.7 has added value in representing the spatial characteristics of precipitation and temperature in certain regions. However, there are still limitations in simulating precipitation over the Amazon Basin, particularly in summer.