Climate and weather factors modulating river flows in southern Angola

The large-scale circulation and thermodynamic fields that modulate the flow of the Kavango River in southern Angola during austral summer are studied. According to composite patterns constructed from National Center for Environmental Prediction (NCEP) data, enhanced river flow is associated with an anomalous wave train of upper level winds that emanate from the North Atlantic. Sea-surface temperatures (SST) show a warm-north/cool-south Atlantic dipole condition as the Kavango River rises. Correlations are analysed with respect to the Kavango River flow and a 0 lag value of -0.41 is found for the upper zonal wind over the North Atlantic. Rainfall over the African Sahel region is positively linked with Kavango River flow at 6 month lead time (r = +0.34). The work is extended to the event scale and it is found that winds draw tropical moisture over southern Angola in response to an anomalous low-high pair and bifurcated subtropical jet stream. A continental scale sea breeze circulation amplifies the convection during afternoons. Knowledge of run-off into Namibia is critical to the management and planning of water resources in the northern Kalahari savanna. Copyright (C) 2009 Royal Meteorological Society