Estudo numérico da interação entre convecção rasa e radiação com ênfase no ciclo diurno do balanço de energia à superfície.

Abstract

The objective of this work was investigating the effect of shallow convection on the diurnal cycle of the surface energy budget. The focus is on the role the cloud shading plays on the configuration of the surface convective forcing. The model used was the Brazilian Regional Atmospheric Modeling System (BRAMS) and the simulations were performed for a forested area located in Ji-Parana, in the state of Rondonia. The study covers the time period of two wind regimes, namely the western and the eastern wind regime period. The model was run for three day for each wind regime. The simulations were performed with two grids, the first one with a horizontal resolution of 80 km and the second grid with 20- km resolution, both centered at Rondonia. Two kinds of experiments were performed: in the first experiment, named SHA, the model had no interaction between shallow convection and radiation. In the second type of experiment, named RAD, shallow convection interacts with radiation. In addition, simulations were performed with initial soil moisture of 50 % and of 70 % for each set of experiments, for both wind regimes. The observed data were from the Wet Season Atmospheric Mesoescale Campaing of the Large-Scale Biosphere- Atmosphere Experiment in Amazonia – WETAMC/LBA. The results show that the consideration of the interaction between shallow cumulus and radiation leads to more realistic simulations. This is more pronounced around the local noon and early afternoon, when the shallow cumulus activity reaches a maximum. The surface fluxes and the cumulus cover were very sensitive to the variations in the radiative forcing. Even though, from a qualitative viewpoint, there is an improvement of the quality of the simulated fluxes, it became evident a model flaw in representing these fluxes during the first hours of the diurnal cycle.