The study proposes to examine variability of summer precipitation over South America and Africa, on time scales including from the event to the interannual. Satellite-derived and ground-based observations will be examined. Modeling tools used to identify and understand various physical mechanisms influencing tropical precipitation will be a linear model, a dry non-linear model, idealized and realistic general circulation models and a meso-scale model. NCEP and ECMWF reanalyzes as well as CSM model output will also be analyzed. The work is important because it will enhance understanding regarding climate variability over Africa and South America and this could have important societal impacts.