Tests with parameterization of convection in cases of intense rainfall in mountainous regions

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Wednesday, 7 January 2015
Daniela Carneiro Rodrigues, INPE, Cachoeira Paulista, Brazil

Intense precipitation events are the commonest cause of Natural Disasters world- wide, including Brazil, mainly on regions of complex topography. One of the most striking forms of the influence of topography on atmospheric conditions is its strong control over the distribution of rainfall, with common large horizontal variations of precipitation in mountain regions. It has been found in the analysis of simulations of precipitation the of regional Eta model a deficiency of the model to simulate rainfall heavy over regions of complex topography, showing a trend of underestimation of precipitation downwind and at the top of the mountains. The objective of this study was to test some adjustments in the scheme precipitation parameterization seeking improvements in the production of precipitation in regions of complex topography of southeastern Brazil (SEB). Eleven cases of Intense rain on the SEB were simulated using the Eta model with spatial resolution of 8 km. Sensitivity tests were applied in the parameterization of convection Bettis-Miller-Janjic and microphysics Ferrier. Were performed a control simulation, used as a reference for comparison, a simulation with inversion in the order called the schemes parameterization of precipitation production, simulations with variations in DSP parameter settings in the moisture profile reference convective parameterization BMJ and simulations by changing the criteria the trigger convective depending on the altitude. The results show that the inversion when microphysics is called before the convective scheme, it has higher activity, producing larger quantities of stratiform precipitation mainly on the regions of high topography. The inclusion of a function parameter setting convective DSP depending on topography resulted in a significant increase in convective precipitation over the top of the mountains. The results regarding the spatial distribution showed that changing the temperature of the convective layer resulted in a high production precipitation convective in the regions of high topography, however, a change was observed in the pattern precipitation over the whole area, impacting the reduction excessive of rainfall over regions of low topography compared to the control simulation.