An animation of El Nino If you have an MPEG animation viewer, and sufficient memory, you can view an animation of El Nino which shows the changes in monthly sea surface temperature in the tropical Pacific Ocean. The animation is about 1 Megabyte in size. As you view this animation, you will see the warm water spreading from the western Pacific to the eastern Pacific during 1991. The bottom panel in the animation, labeled anomalies, shows how much the sea surface temperature for each month is different from the long term average for that month. The red color in the anomalies plot indicates that the temperature of the water is much warmer than is normal for that month.
Blue color indicates that the water is much cooler than is normal for that month.
Time is increasing downwards from 1986 at the top of the plot, to the present, at the bottom of the plot. Cold tongue temperatures vary seasonally, being warmest in the northern hemisphere springtime and coolest in the northern hemisphere fall. The red color on the left is the warm pool of water typically observed in the western Pacific Ocean. El Nino is an exaggeration of the usual seasonal cycle. There is another El Nino in 1991-1992, and you can see the warm water penetrating towards the east in the northern hemisphere spring of 1992.