Transição de cúmulos rasos para cúmulos congestos na configuração do ciclo diário da precipitação.

Abstract

The aim of this work was to study the role played by congestus cumulus on the configuration of the Amazonian deep convection. The shallow convection scheme of the BRAMS model was adjusted by inserting the stage of transition from shallow to congestus cumulus, since its parameterization is even more important when the study refers to tropical regions. Thus, three experiments were performed: in the first control experiment (EXP-CTRL), the model was initialized in its original form and the others (EXP-AJUST1 and EXP-AJUST4), the model was run to the same conditions as the EXP-CTRL but with due adjustment made in BRAMS code, the model has the capacity to produce some precipitation after the congestus cumulus stage, before the formation of deep convection. The model was integrated for a period of 270 hours, with spatial resolution of 20 km, for a domain centered on the Amazon. Analysis of the mean daily cycle of convective precipitation and thermodynamic vertical profile was performed in two distinct areas, located in Manaus-Amazonas. Overall, the results show that there were important differences in the thermodynamic profile of the lower troposphere due to the implementation of new setting in the BRAMS code. It was observed that the effect of precipitation produced by congestus intensified and displaced the maximum values of moistening and heating rates by the shallow convection in the adjusted experiments, as a consequence of part of its precipitation being used to wet and cool the surface, thus increasing the heat fluxes and the moisture at the lower levels of the atmosphere. The timing of maximum congestus activity substantially reduced convective precipitation between 08 and 12 LT, mainly in EXP-AJUST4 than EXP-AJUST1, as it stabilized the environment at that time, postponing the process of deep convection formation, which had its maximums between 16 and 19 LT. That is, a delay of the deep convection occurred as response to the preconditioning of the atmosphere by the congestus cumulus. This result agrees with observational studies.