This series of six images shows the movement of atmospheric water vapor over the Pacific Ocean during the formation of the 1997 El Niño condition. Higher than normal ocean water temperatures increase the rate of evaporation and the resulting warm moist air rises into the atmosphere altering global weather patterns. Data obtained by the Microwave Limb Sounder (MLS) on NASA's Upper Atmosphere Research Satellite (UARS), from late February 1997 to late December 1997, show the movement from the western Pacific to the eastern Pacific of high levels of water vapor (red) at 10 kilometers (6 miles) above the surface. Areas of unusually drier air (blue) appear over Indonesia. December 1997 data also show a rapid increase of water vapor off the coast of South America, the result of very high water temperatures in that region.