The impact of the South Atlantic Ocean on regional climate

Author(s)

Andréa Sardinha Taschetto

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto Oceanográfico (IO/DIDC)
• Defense date: 2006-06-30

Examining board members

Ilana Elazari Klein Coaracy Wainer; Edmo Jose Dias Campos; Leila Maria Vespoli de Carvalho; Pedro Leite da Silva Dias; Joseph Harari

• Advisor: Ilana Elazari Klein Coaracy Wainer

Abstract

This work aims to study the impact of South Atlantic sea surface temperature (SST) on regional atmosfheric circulation. In order to achieve this purpose we used the atmospheric global circulation model Community Climate Model (CCM 3) from National Center for Atmosfheric Research (NCAR). the effects of South Atlantic on atmosphere are examined through two sets of numerical simulations (ensemble) generated with different SST configurations. The integrations were forced by SST from observational data over two domains: global ocean and South Atlantic from 20ºS to 60ºS. Looking for the reduction of the internal variability of the atmosphere and for increase of the response from the local SST forcing, a forcing, a special treatment was applied to the ensembles. The statistical methodology used in this study includes simple analysis such as climatology, variance and correlation as well as Empirical Orthogonal Functions and Singular Value Decomposition. the comparasion between the numerical experiments showed that the South Atlantic influences the interannual variability of precipitation over South America, especially with respect to the intensity and geographic position od South Atlantic Convergenge Zone (SACZ) during the austral summer season. The anomalous SST of the Subtropical South Atlantic induces the heat exchange between ocean and atmosphere, which togeter with a cyclonic circulation near the southern Brazilian coast, advects relatively moist and warm air to the oceanic part of SACZ. The increase of convection over this band inhibits the solar radiation in the surface, preventing the continuous increase of SST (negative feedback). This work also shows the importance of SST from the South Atlantic and Equatorial Pacific in modulating the intensity and position of ITCZ during the autumn and winter monhths. This study also confirms the El Niño - Southern Oscillation (ENSO) as a remote impact factor controling the intensity of rain over southern Brazil mainly during winter. (AU)

• FAPESP's process: 02/01211-0 - Ocean-atmosphere interaction in the South Atlantic ocean and its global impact
• Grantee: Andréa Sardinha Taschetto
• Support Opportunities: Scholarships in Brazil - Doctorate