Invasões inter-hemisféricas de sistemas com escala sinótica em altos níveis sobre o Atlântico Tropical e sua associação a fenômenos adversos no Nordeste do Brasil

Abstract

This work aimed to identify the formation processes and influences of: 1) Upper Tropospheric Troughs from the Northern Hemisphere (UTT-NH), 2) Upper Tropospheric Cyclonic Vortexes (UTCVs) at low latitudes and 3) Upper Tropospheric Anticyclonic Centers (UTACs) on circulation and occurrence of adverse phenomena in Northeast Brazil. General analyzes were carried out daily, at 0Z, from 1991 to 2020, based on satellite images and ERA5 reanalyses. The number of cases were registered for the period between 2011 and 2020. Typical cases from each system were selected to identify associated phenomena. Information about the phenomena was obtained from surface stations and METAR code messages. The main results are: 1) UTT-NH invasions over the Southern Hemisphere occurred during the passage of frontal systems and UTCVs from the Northern Hemisphere. The maximum UTT-NH invasions were observed during the southern summer, in January. 2) The presence of UTT-NH modified the formation, positioning and intensity of UTCVs at low latitudes. Changes in the precipitation regime were observed due to the interaction between UTCVs and UTT-NH. The displacement of UTCVs showed a relationship with the positioning and intensity of the ridges of subtropical anticyclones in both hemispheres. 3) UTACs formed during the austral summer, in the edge of an UTT-NH, intensified the displacement and formation of convective clouds in the western sector of the UTCVs. UTACs formed between the end of autumn and the beginning of the austral spring showed distinct processes and were classified as High Level Anticyclones. Anticyclones formed from a zonal ridge at the upper troposphere over the South Atlantic peaked in August, moved westward and formed due to the amplification of the ridge after the passage of frontal systems on the west coast of Southern Africa. Anticyclones formed from disturbances in the Pacific had a maximum in June, displacement to the east and were similar to the Bolivian High. The presence of Anticyclones over the NEB was marked by good weather, with the occurrence of weak precipitation in the region of confluence between the two types of anticyclone or after their dissipation.