Featured on the Cover: December 1999
The cover features two images of the Pacific Ocean produced using sea surface height measurements taken by the U.S./French TOPEX/Poseidon satellite. The image on the left displays sea surface height relative to normal ocean conditions (shown in green) on November 10, 1997, and reveals a large volume of extra warm surface water (shown in white) that forms the core of El Niño. The image on the right from February 27, 1999, shows a low sea level or cold pool of water dominating the equatorial Pacific Ocean (shown in purple and blue), which is commonly referred to as La Niña. See Using TOPEX Satellite El Niño Altimetry Data to Introduce Thermal Expansion and Heat Capacity Concepts in Chemistry Courses by Harvey F. Blanck on pages 1635-1638. Images by NASA/JPL/Caltech, used with permission. The cover was designed by Betsy True.

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