Middle Tropospheric Cyclonic Vortex in Northeastern Brazil and the Tropical Atlantic

Abstract

Middle Tropospheric Cyclonic Vortices (MTCVs) are observed in the tropical region of the Southern Atlantic, with their center located between 700 and 400 hPa. The analysis of MTCVs’ frequencies, location and duration over 3 years (2008–2010) was the principal goal of the present study. MTCVs have been identified and analyzed using the NCEP reanalysis data at the nine levels. About 232 MTCVs were observed each year. More frequently the MTCV centers were observed at the 700 hPa (41 % of all days with vortex). MTCVs were registered during all seasons (6–12 MTCVs per month, on average). The MTCVs’ frequency only slightly varied over seasons with the lowest value in spring. MTCVs were predominantly (71 %) short and lasted less than 12 h. The vortices persisting longer than 30 h were detected more frequently in summer and rarely in autumn. MTCVs were observed more frequently (86 %) between 6 and 18°S over the ocean. About nine events per year were observed over the continental region between 9 and 21°S in summer and winter, and between 4 and 11°S in autumn and spring. One MTCV event is considered in detail.