Interannual relations between South American rainfall and tropical sea surface temperature anomalies before and after 1976

The differences between 1948-1976 and 1977-2002 periods in the interannual relationships of South American precipitation with sea surface temperature (SST) indices in selected oceanic sectors are documented using correlation analyses. For the total correlation between the eastern equatorial Pacific (EEP) and tropical South Atlantic (TSA) indices and the precipitation, the differences between the two periods reflect, in part, the El Nino-Southern Oscillation (ENSO) teleconnections over South America, with the Pacific decadal oscillation (PDO) background acting to enhance (weaken) the correlations when ENSO and PDO are in the same (opposite) phase. For the total correlation between the tropical North Atlantic (TNA) and southwest South Atlantic (SWA) indices and precipitation, the results here suggest that the differences between the two periods might be reflected as variations in the Bolivian high-pressure system. Both the TNA and TSA indices may act to weaken the positive ENSO relations with precipitation over central and eastern Brazil during the cold PDO phase. These analyses provide indications that the ENSO relationship with the TSA shows differences between the two analysed periods. Copyright (C) 2008 Royal Meteorological Society