Convergência do fluxo de umidade verticalmente integrada e os prognósticos do modelo WRF

Abstract

In the South America the Low-Level-Jet (LLJ) and the South Atlantic Convergence Zone (SACZ) are import regions with fast moving ribbon of air, in the lower level of the atmosphere, which transport and supply most of the moisture to the long lasting and intense precipitation cloud clusters, occurs in Brazil. These systems act, respectively, over the South and Southeast of Brazil, especially in the warm seasons. The non-hydrostatic mesoscale Weather Research and Forecasting (WRF) model hourly predictions output, with 18 km grid space resolution and 35 vertical levels, have been used in the analysis of the Moisture Flux Convergence (MFC) and the Vertically Integrated Moisture Flux Convergence (VIMFC) fields to explore the importance of these fields on short range forecasting activities. The model integration has been made for the whole year of 2011 with initial and boundary conditions of the GFS (Global Forecasting System) model. Several events of intense precipitation, occurred during the 2011 year over Brazil associated with LLJ and SACZ, have been analyzed and two of them are presented. The results present the importance of the MFC and VIMFC fields for short term forecast, especially in the prognosis of these fields forecasting within three hours later the occurrence of the storms with intense precipitations. The study show that i) the VIMFC prognosis indicate good agreement with the location of developed clouds, when were compare with the satellite images in the three hours after; ii) the VIMFC prognosis, mainly at mid-latitudes proved viable in aid to forecast storms which were caused by precipitation clusters; iii) the values MFC more accented were found between the levels of 700 and 920 hPa, allowing display in which levels the MFC weakened or intensified.