Using the Firefly optimization method in the convective parametrization of the model BRAMS to simulate the diurnal cycle of precipitation in South America

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Wednesday, 7 January 2015
Ariane F. dos Santos, National Institute for Space Research, Cachoeira Paulista, SP, Brazil; and .. S. R. Freitas, M. A. Gan, J. G. Z. de Mattos, H. F. de Campos Velho, and G. Grell

The mean diurnal cycle of precipitation of January 2006, 2008 and 2010 over South America was performed using the model Brazilian developments on the Regional Atmospheric Modeling System (BRAMS). The mean diurnal cycle was compared with the mean diurnal cycle of precipitation estimated by the satellite of the project Tropical Rainfall Measuring Mission (TRMM).The model simulates the maximum of precipitation about 3 hours earlier than observed. To improve the representation of the maximum of precipitation, it was considered an inverse problem of parameter estimation in order to obtain a weighted average using different choices of closures of the convective parameterization scheme of the BRAMS. The inverse problem was solved as an optimization problem using the optimization algorithm Firefly (FY). We attempted to minimize the objective function given by the square difference between the model and TRMM. New mass flux associated with each closure was obtained from the weighted average of a set of weights obtained from the FY, generating a new simulation of diurnal cycle of precipitation. The results indicated a better representation of the rates of heating and drying of the atmosphere. Consequently, simulations of precipitation closest to the observations were obtained. The occurrence of maximum rainfall over the northwestern and southeastern South America occurred about 3 hours later in time compared with the model without weighted mass fluxes.