Atmospheric Circulation in the Furnas Reservoir Region, MG: Sensitivity Experiments with RegCM5 in Convection-Permitting Mode

Abstract

In the 1950s, the Furnas reservoir was created, an artificial lake surrounded by hills, for the operation of the Furnas Hydroelectric Power Plant in southeastern Brazil. Along the shores of the Furnas reservoir, there are no meteorological stations, and only three are found at a distance greater than 10 km from the reservoir, which makes it challenging to assess the lake's influence on the local climate. To address this issue, the Regional Climate Model version 5 (RegCM5) was run in convection-permitting (CP) mode for two months, with a horizontal resolution of 1 km, to investigate the near-surface atmospheric circulation patterns around the reservoir. Three numerical experiments were conducted using RegCM5-CP nested in ERA5 reanalysis: a control simulation (CTRL), an experiment where the topography was assumed to be flat throughout the domain (expTOPO), and an experiment where the water body was replaced by vegetation (expVEG). The first month of simulation in each experiment was excluded from the analysis as it was considered a spin-up period. RegCM5-CP has good performance in simulating the diurnal cycle of the 2-m air temperature and reasonable performance for the 10-m wind intensity compared to observed data from three meteorological stations in the domain of simulation (but distant from the reservoir shore). Despite the geographic complexity of the Furnas reservoir, the experiments revealed coupling between lake and valley breezes during the daytime and land and mountain breezes during nighttime in different segments of the reservoir, such as in Guapé (near the dam). However, mountain-valley breezes are more dominant.