Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Weekly time plot of sea surface temperature anomalies (°C) in the central eastern (Niño 3.4), eastern (Niño 3) and coastal upwelling (Niño 1 + 2) regions of the equatorial Pacific Ocean from January 1997 to April 1998. El Niño onset and peak (based on ONI index) and study period are highlighted.
