Figure 3. Enhancement of the tropical ocean observing system in the course of the international TOGA Program (1985-1995). Open circles are tide gage stations fixed on continental or island coastlines; black squares and diamonds are instrumented buoys that are held in place by deep anchors; arrows are instrumented, drifting buoys; continuous lines are the heavily-traveled lanes of commercial ships that supply observations of sea water temperature and other conditions on a voluntary basis. The denser observing network shown in the lower diagram, which remains in place, led to the breakthroughs that have made it possible to predict El Niño and La Niña events. (From McPhaden et al., Journal of Geophysical Research, vol 103, PP 14169-14240, 1998.)