ENSO AND THE NATURAL VARIABILITY IN THE FLOW OF TROPICAL RIVERS

This paper examines the relationship between the annual discharges of the Amazon, Congo, Paran ii, and Nile rivers and the sea surface tempe rature (SST) anomalies of the eastern and central equatorial Pacific O cean, an index of El Nino-Southern Oscillation (ENSO). Since river sys tems are comprehensive integrators of rainfall over large areas, accur ate characterization of the flow regimes in major rivers will increase our understanding of large-scale global atmospheric dynamics. Results of this study reveal that the annual discharges of two large equatori al tropical rivers, the Amazon and. the Cungo, are weakly and negative ly correlated with the equatorial Pacific SST anomalies with 10% of th e variance in annual discharge explained by ENSO. Two smaller subtropi cal rivers, the Nile and the Parana, show a correlation chat is strong er by about a factor of 2. The Nile discharge is negatively correlated with the SST anomaly, whereas the Parana river discharge shows a posi tive relation. The tendency for reduced rainfall/discharge over large tropical convection zones in the ENSO warm phase is attributed to glob al scale subsidence associated with major upwelling in the eastern Pac ific Ocean. (C) 1997 Elsevier Science B.V.