January 27, 1998
(Top image - P49502)
This image shows differences in atmospheric water vapor relative to a normal (average) year in the Earth's upper troposphere about 10 kilometers (6 miles) above the surface. The measurements were
taken by the Microwave Limb Sounder (MLS) instrument aboard NASA's Upper Atmosphere Research Satellite (UARS). These data, collected in late December 1997, show higher than normal levels of water vapor (red) over the central and eastern Pacific which indicate the presence of an El Nino condition. At the same time, the western Pacific (blue) is much drier than normal. The unusually moist air above the central and eastern Pacific is a consequence of the much warmer than normal ocean waters which occur during El Nino. Warmer water evaporates at a higher rate and the resulting warm moist air rises and forms tall cloud towers. In the tropics, the warm water and the resulting tall cloud towers typically produce large amounts of rain. These data show significant increases in the amount of atmospheric moisture off the coast of Peru and Ecuador since measurements were made in November 1997. The maximum water temperature in the eastern tropical Pacific, as measured by the National Oceanic and Atmospheric Administration (NOAA), is still higher than normal and these high ocean temperatures are likely responsible for an increase in evaporation and the subsequent rise in humidity.
(Bottom image - P49503)
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.
Source: Jet Propulsion Laboratory
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