资源环境科技发展态势分析平台

An analysis of two groups of near-surface intense cyclonic vortices, one off the southeastern Brazil coast and the other off the Mozambique coast, in the period 1979-2012 is undertaken for comparison of their characteristics with the help of the TRACK algorithm and the NCEP2 Reanalysis data sets. The aim is to understand the nature of intense cyclogeneses in those two subtropical coastal regions. Although the two groups form in almost the same latitude belt and under similar conditions and thus have some common features, they differ in several evolution and movement characteristics. The South American intense cyclones are more frequent. They move rapidly into southern South Atlantic while the African cyclones remain quasi-stationary during the first 2 days of their life time. Thermal structures show that the Mozambique Channel region presents more conditional instability. The South American intense cyclones present more kinetic energy than their counterparts in the first 2 days. The precipitation around the South American cyclones decreases gradually. The Mozambique Channel cyclones gain kinetic energy after moving away from the Madagascar Island and preserve their baroclinity longer and therefore the mean precipitation rate around their centres remains constant. The sea surface temperature, the geographical features and the circulation characteristics of the two regions are responsible for the differences. Eventually, after 4 days of their formation, cyclones of both the groups join the Southern Hemispheric extratropical storm-tracks.