La Nina
D1. Physical and chemical oceanography and marine meteorologyDefinition
Cool phase of ENSO with enhanced trade winds and cooler eastern equatorial Pacific.
La Nina is the cool phase of ENSO: trade winds strengthen, the eastern equatorial Pacific thermocline shoals, upwelling intensifies, and the cold tongue deepens and spreads west. It is the rough mirror of El Nino, favoring an active Atlantic hurricane season, drought in the southern United States, and wetter conditions over Australia and Southeast Asia. Multi-year La Nina events have become a focus of decadal-variability research.