Um estudo observacional da incursão de sistemas frontais no nordeste brasileiro e sua influência na atmosfera do Centro de Lançamento de Alcântara (CLA) / Observacional study of the incursion on frontal systems on northeast Brazil and its influence in the atmosphere of the Alcantara Launching Center (CLA)

Priscila da Silva Tavares

In this work, an observational synoptic configuration pattern study was performed over the South America (SA) and in the South Atlantic (SAO) and South Pacific Oceans (SPO), in events of Frontal Systems (FSs) that reached the Brazilian northeast coast and created an intense cloudiness in the region of the Alcântara Launching Center (ALC). Seven cases were selected, during all seasons of the year. They were analyzed since its incursion on south of Brazil until its maximum incursion in the country seeking to identify the possible synoptic mechanisms that favored its motion. After that, the FS influence was investigated, in the ALC atmosphere, through the meteorological surface parameters analysis. It was noted an incidence of cyclogenesis in the surface, commonly noticed in the Rio Grande do Suls east coast. About the SAO and SPO, it was noticed values of sea level pressure (SLP) in the region South Pacific Subtropical High (SPSH) more intense than in the South Atlantic Subtropical High (SASH) and its movements to east. In most events, the SPSH enter the south of the SA, around 40°S, favouring anticyclogenesis, usually located in the north/central of Argentina. The anticyclone formed on the continent has expanded and continued the movement to east, contributing to the advancement of FS. In middle and high levels, happened the amplification of the frontal rough associated to surface systems, which it was intensified meridionaly and extended from middle latitudes (55°S) until the tropics, and some of them providing the formation of a cyclonic vortex (subtropical). In high levels, the Subtropical Jet (SJ) presented week and was noticed in events of summer and austral spring, the formation of Upper Troposphere Cyclonic Vortex (UTCV), that act close to Northeast Brazil (NEB), only in the later days of the event. With this VCANs formation, the SFs stayed stationary in the NEB contributing to the formation of South Atlantic Convergence Zone (SACZ). Besides it has been also observed in the day of this incursions of this events in the south of Brazil, weak intensity of SFs was lately intensified in the boundaries of the States Minas Gerais/MG and Rio de Janeiro/RJ, because of the interaction with lefts of another SF present in the region. In the CLA atmosphere, we can notice that the atmosphere pressure and relative humidity falls, with the incursion of the NEBs FS and after they raises, with its movement through the region. The air temperature presented a little increase from the NEBs incursion, decrease with permanence and increasing returns after FSs passage. The wind velocity increases lightly with the incursion, and then decreases with the FSs movement. In the most of events of precipitations happened in Alcântara.

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