Regional assessment of atmospheric CO₂, CH₄ and CO concentrations in Southern Brazil using WRF-Chem under present and energy transition scenarios

Abstract The objective of this study was to evaluate the spatial and temporal distribution of greenhouse gases (CO₂ and CH₄) and the atmospheric pollutant CO in Santa Catarina, Brazil, and to analyze the impacts of energy transition scenarios on their atmospheric concentrations. The methodology was based on the development of a regional emissions inventory, including stationary and mobile road sources, followed by the application of the WRF-Chem atmospheric model (Weather Research) and forecasting with Chemistry. The model was configured with a horizontal resolution of 5 km and 31 vertical levels, integrating meteorological data from ERA5 and chemical boundary conditions from GEOS5 and WACCM. A baseline scenario (2022) and prospective scenarios for 2030, 2040, and 2050 were simulated, considering the gradual replacement of fossil fuels with biofuels. The results of the WRF-Chem modeling showed higher concentrations of pollutants in metropolitan and industrial areas and along major road corridors, with marked diurnal variability, including peaks at 8 am and 4 pm, and high concentrations at night due to the stability of the atmospheric boundary layer. Prospective simulations indicated gradual reductions in atmospheric concentrations, reaching decreases of approximately 6–8% for CO, 15% for CO₂, and up to 17% for CH₄ in the 2050 scenario. The model demonstrated high sensitivity to changes in the emissions inventory, demonstrating its application in the coupled representation of physical and chemical processes. Thus, WRF- Chem proved to be an effective tool to support public policies for climate mitigation and regional energy planning.