Using Meteosat-10 imagery to identify cloud patterns associated with an anticyclone in Brazil.
22 October 2020
07 January 2016
By Humberto Alves Barbosa (Laboratório de Análise e Processamento de Imagens de Satélites ), Salomão de Sousa Medeiros (Instituto Brasileiro do Semiárido ) and Carlos Pinto Sa Silva Neto (Sistema Meteorológico do Paraná )
The Meteosat-10 HRV image on 07 January (Figure 1) shows a high pressure centre (Bolivia High) at high levels (250 hPA) which is predominant in South America's atmospheric circulation during the summer.
In this example, it is observed that from the synoptic point of view the instability in the region is dynamically supported by upper level divergence in the transition zone of the Bolivia High (BH) and the cyclonic circulation in the vicinity of Northeastern Brazil (CVNE) in the upper troposphere.
Cloud patterns are associated with the Bolivian High (BH) in Brazil, which have an intrinsic relationship with deep convection. The structure of the Bolivian anticyclone-Nordeste low system is a short-wave train across South America modulated by the long-wave regime. The short-wave train exhibits a monsoon vertical phase reversal in the mid-troposphere and a quarter-wave phase shift relative to the divergent circulation. The Bolivian anticyclone (BH) could help the organization of deep convection in its southern flank by the interaction with short waves and intensified subtropical jet (strong BH). It distinguished Ci clouds (Figure 1) and enhanced convection (Figure 2) over Brazil.
The BH is well-defined and is situated over south-western Amazonia near Bolivia, and the CVNEs are found over the south-western Atlantic Ocean (Figure 2).
The rainfall at this time of the year seems to be associated with the presence of upper level divergence in the transition region between the opposite circulation systems: the BH and the CVNE.
BH divergence could help the organisation of deep convection in its southern flank by its interaction with short waves as well as by its intensified subtropical jet.
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