A case study of a winter heavy rainfall event over the Serra do Mar in Brazil

Marcelo E. Seluchi, Sin Chan Chou, Marcelo Gramani

Abstract


Serra do Mar is a mountainous region vulnerable to landslides due to frequent summer heavy rainfall and steep slopes. These mountains are located in Southeastern Brazil and lie along the coastal region. Major cities, industries, roads and pipelines are established in the Serra do Mar. A reference of landslides occurred in the winter of 2004. This is a rare case in the dry season and the civil defense was caught unprepared. We investigate the causes of these landslides in order to provide some guidance to forecasters and policy makers. Rain was mainly from stratiform clouds associated with a relatively intense cold front which persisted for about 6 days in the region. The cold front became stationary on the coast of the State of Sao Paulo as the post-frontal anticyclone, which was initially cold, acquired a barotropic structure and, consequently, a semi stationary behavior. The large scale circulation determined the persistence of southerly and southeasterly winds near the surface. After reaching the continent, these winds were lifted by the Serra do Mar mountain chain. The progression of a shortwave trough to upper levels was not the major cause of heavy precipitation, but contributed to enhance the thermodynamic instability and increase rainfall, which caused the landslides in the Serra do Mar.

Keywords


heavy rains; landslides; orography; Brazil

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DOI: http://dx.doi.org/10.22201/igeof.00167169p.2011.50.1.121

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