(Climatic patterns of upper level cyclonic vortex over northeast Brazil). Padroes climaticos dos vortices ciclonicos em alto niveis no nordeste do Brasil.

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In this work the circulation patterns associated with upper level cyclonic vortices (VCANs) over the Northeast Brazil and Tropical South Atlantic have been studied. Results from the synoptic climatology for the period January 1980 - December 1989 confirm that VCANs form in the upper troposphere, with maximum cyclonic vorticity at 200 hPa and a cold core at 300 hPa. Most of the VCANs originate over Tropical Atlantic, and they are more frequent during the summer months. In general the VCANs extend downward to 500 hPa and rarely they reach 700 hPa. They have westward inclination with height and the cold core is located to the east or southeast of their center. The average life time is 7.1 days. During El Nino years, the VCANs are deeper in the vertical, while during La Nina years they are confined at upper levels. It has been confirmed that VCANs originate from the amplification of the ridge associated with the Bolivian high (BH). Such amplification can be caused by the incursion of the midlatitude frontal systems, or by troughs in the North Pacific or in the North Atlantic aligned with BH in NW-SE or NE-SW directions. The ...

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