Abstract
A Zona de Convergência do Atlântico Sul (ZCAS) é uma alongada e persistente banda de intensa convecção que na época de verão e com certa frequência se estende da Amazônia ao oceano ao largo das costas brasileiras, exercendo papel significativo no regime pluviométrico do País. Juntamente com suas congêneres do Pacífico e do Índico, constitui uma nova categoria de organismo meteorológico de larga escala, identificado a partir da década de 1970 através da análise de observações de satélite. A explicação do fenômeno é ainda um desafio para a meteorologia e climatologia; essencialmente, resulta de uma intensa interação entre sistemas tropicais e de latitude média. Neste trabalho, recapitulamos uma parte da evolução histórica dos conhecimentos sobre o assunto, incluindo, além das contribuições de pesquisadores brasileiros, os providenciais estudos japoneses comparando a ZCAS com a Baiu, e apresentamos descrições resumidas de eventos de ZCAS no Brasil. Como complemento, reportamo-nos a dois eventos de precipitações destrutivas no Estado de São Paulo, de natureza frontal, a comparar com a atuação da ZCAS.
Highlights
The term “Zona de Convergência do Atlântico Sul” came to be a part of the Brazilian meteorological language – generally abbreviated ZCAS (SACZ - South Atlantic Convergence Zone - in English) and pronounced “zácas” – beginning in the 1980s
SACZ, due to the close association of its Asiatic counterpart with the Indian monsoon, has contributed in recent years to the adoption of another new term in Brazilian meteorology: “South American monsoon system” (The elder idea of a South American monsoon was a cause for debate and generally rejected by climatology) (GAN et al 2016)
A phenomenon typical of the rainy season which happens between May and July in China and Japan, the Baiu, or Mei-ju (“plum rains”), is a kind of semi-stationary front characterized by an extensive band of strong convective precipitation, when in its active phase (Glossary of Meteorology, AMERICAN METEOROLOGICAL SOCIETY, 2000, term South Atlantic convergence zone, p. 705)
Summary
The term (in Portuguese) “Zona de Convergência do Atlântico Sul” came to be a part of the Brazilian meteorological language – generally abbreviated ZCAS (SACZ - South Atlantic Convergence Zone - in English) and pronounced “zácas” – beginning in the 1980s. From the wider viewpoint of the general circulation of the atmosphere, the SACZ constitutes a new class of large-scale phenomena – the so-called “tropical convergence zones”, which are four in the planet: the one of the South Pacific, of the Asiatic East (or Baiu in Japan), of the South Atlantic, and (the less expressive one) of the South Indian These four convergence zones present common characteristics – the main one the moisture convergence (coming together of moist winds) in low levels – and significant differences, some of them attributed to local or regional geographical factors (continental, maritime and orographic), others attributed to remote sources and propagated by the atmosphere itself through the so-called “teleconnections” (factors carried by global circulation systems such as Rossby waves and jet stream). There already is an excellent review by QUADRO et al (2016) published in Climanálise, about SACZ studies carried out in Brazil and in other countries over the last 30 years
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