The role of the tropical and south Atlantic variability on the northeast Brazil climate in El Niño

Abstract

The role of the Tropical and South Atlantic variability on the rainfall in the Northeast (NE) Brazil to increase the potential for its predictability has been the main objective of Dr. Regina R. Rodrigues postdoctoral research sponsored by FAPESP (Contract # 2007/03279-5). This is also part of an ongoing collaborative effort between Dr. Campos (IOUSP) and Dr. Haarsma (KNMI), which has been supported by FAPESP since 2001 (Contract # 2001/10965-6, 2004/01850-9, 2005/04315-0, and 2006/03949-8). NE Brazil rainfall is associated with the position of the Intertropical Convergence Zone (ITCZ), which in turn is strongly linked to the meridional gradient of sea surface temperature (SST) anomalies in the Tropical Atlantic. It is also well known that years of severe droughts tend to be preceded by anomalously warm equatorial Pacific waters (El Niño years), suggesting that the Pacific SST anomalies are also important in determining the NE Brazil rainfall. However, the precipitation in NE Brazil is not always below the average during El Niño years. Preliminary data analysis suggests that the response of the NE Brazil rainfall to El Niño is determined by the preconditioning of the South Atlantic and South Tropical Atlantic SST anomalies, which in turn may or not be caused by El Niño telecommunications. We propose to investigate the mechanisms that cause SST anomalies in the South and Tropical Atlantic during El Niño years using a coupled ocean-atmosphere general circulation model (Speedy-MICOM). In particular, a sensitivity experiment will be implemented by running the Speedy-MICOM with specified El-Niño variability. Results of the cold tongue predictability run, already performed by Dr. Haarsma in KNMI, will be analyzed to check if there is real predictability in the model. This proposal requests funds for Dr. Rodrigues to visit KNMI during May and June to execute the two aforementioned tasks. (AU)