1997-98 El Niño event, water temperature and sea-surface topography in the equatorial Pacific Ocean – (a) January 1997; (b) June 1997; (c) November 1997; (d) March 1998 The images show a combined perspective of the El Niño-induced change in sea temperature below the surface as measured by NOAA’s Tropical Atmosphere/ Ocean (TAO) moorings, the sea-surface topography as viewed from space by the NASA Ocean Topography Experiment (TOPEX) radar altimetry satellite, and sea-surface temperature observed by NOAA’s Advanced Very High- Resolution Radiometer (AVHRR) sensor, for the period from January 1997 to March 1998. Credit: NASA Goddard Space Flight Center, Scientific Visualization Studio; NOAA Pacific Marine Environmental Laboratory.