Figure 2.11 Winter and summer monsoon wind patternsEL NIÑO—SOUTHERN OSCILLATION (ENSO)
La Nada (Normal Conditions)
During normal conditions, easterly trade winds move water and air warmed by
the sun toward the west (Walker circulation). The ocean is generally around 24
inches (60 cm) higher in the western Pacific and the water is about 14°F warmer.
The trade winds, in piling up water in the western Pacific, make a deep—450
feet (150 m)—warm layer in the west that pushes the thermocline down while it
rises in the east. The shallow—90 feet (30 m)—eastern thermocline allows the
winds to pull up nutrient-rich water from below, which increases fishing stocks.
The western side of the equatorial Pacific is characterized by warm, wet low-
pressure weather, as the collected moisture is released in the form of typhoons
and thunderstorms.
Figure 2.12 Normal conditions