Vórtices ciclônicos de altos níveis do Nordeste brasileiro: sua relação com o transporte de umidade da América do Sul e sua estrutura termodinâmica.

Abstract

The Upper-Tropospheric Cyclonic Vortexes (UTCV) are one of the main synoptic systems responsible for rainfall production in the pre-rainy season over Northeastern Brazil (BNE). In this study, the UTCV were analyzed in different ways. First, a new way of measuring and comparing the intensity of precipitation and the convergence of moisture transport is presented. This method is used to compare the intensity of these quantities in the vortexes and in two areas of high precipitation in the South American continent, the Amazon (AMZ) and the La Plata Hydrographic Basin (LPB). The presented method can be used to calculate the average intensity in an irregular area of any other scalar field and is very useful to allow quantitative comparisons. In addition to this climatological analysis of UTCV intensity, case studies were also carried out that made it possible to advance in the understanding of their thermodynamics. Due to the BNE rainfall irregularity, the analysis of the UTCV behavior in the rainfall distribution over the region is of paramount importance, as it offers subsidies for the improvement of the short-term weather forecast. Satellite images of Geostationary Operational Environmental Satellite (GOES) 12, 13 and 16 from the images database from Center for Weather Forecasting and Climate Studies (CPTEC/INPE) and from GIBBS Service of the National Center for Environmental Information (NCEI) in the infrared and water vapor channels were used to help on events analysis and identification. ERA-Interim reanalysis data was provided by the European Center for Mediun-Range Weather Forecasts (ECMWF). These data were processed on Open Grid and Analysis Display System software for the meteorological fields construction, in order to observe the synoptic and thermodynamic conditions of the systems. Precipitation data were obtained from the Tropical Rainfall Measuring Mission (TRMM) satellite through 3B42 product. The 20-year analysis indicated a changing on moisture flows itinerary of from the Equatorial Atlantic Ocean, however, on the days of vortex development, flow from the AMZ was observed, which transported moisture from west to east, causing part of this moisture transported from the AMZ and the ocean to converge on the vortex area. In the BNE, during the extreme events associated with the UTCV convection, there were records of higher intensity in moisture convergence, reaching to exceed the values of AMZ convergence for a few days. This occurred during the presence of more intense vortexes, where their western peripheries were fixed over the continent. In this context, a moisture transport in South America conceptual model with the addition of information obtained during this study was developed. Further analysis shows that the UTCV thermodynamic structure presented upward movements only in the western periphery, the eastern periphery was characterized by descending movements and strong convective inhibition, allowing the addition of information about these systems to the literature.