Weather Reasearch and Forecasting Model Simulation of a Snowfall Event in Southern Brazil

Abstract

This study evaluates the ability of the Weather Research and Forecasting (WRF) Model to simulate a snowfall event in the southern Brazil. The event in August 2013 was considered one of the most intense in recent years in the region with the highest topographic elevations between the states of Rio Grande do Sul (RS) and Santa Catarina (SC). The Snowfall in the mountain region of RS and SC was associated with the configuration involving a polar anticyclone and the intensification of an extratropical cyclone over the Atlantic Ocean. The WRF simulation results demonstrated the model's viability to predict the event, but without the magnitude representation of the phenomenon. The simulations represented few snow accumulations, with a maximum value of 1.2 mm, and occurred in only two meteorological monitoring stations among the seven evaluated, differently from what was reported in the media. These results may be linked to the simulation of the warmer air temperature near to the surface in relation to the observations, and consequently to the increase in the simulation of precipitation in liquid form. These results were attributed to the choice of WRF Single–moment 6–class (WSM6) microphysics and in the Noah Land Surface Model scheme. Despite these limitations, WRF has proved to be an important tool for predicting the spatial and temporal distribution of snowfall and precipitation in the higher regions of southern Brazil.