Long-Term Rain Forecasts

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Science  25 May 2001:
Vol. 292, Issue 5521, pp. 1451
DOI: 10.1126/science.292.5521.1451a

The ability to anticipate multi-annual regional rainfall patterns is an important part of water resource planning and management. One factor that regulates the amount and distribution of precipitation in North America is the Atlantic Multidecadal Oscillation (AMO), a cycle of North Atlantic sea surface temperature variability with a period of 65 to 80 years.

Enfield et al. outline the geographical pattern of variability in North American rainfall for the last century. They supplement these findings with river discharge data for two representative hydrological provinces and then compare them to the AMO. During warm phases of the AMO, the United States receives lower than normal rainfall, particularly over the eastern Mississippi Basin. Other areas, however, such as Florida and parts of the Southeast, experience more precipitation. Because the current trend in the AMO is toward higher temperatures, the forecast is for decreased annual rainfall over much of the United States. The nonstationary pattern of the expression of El Niño-Southern Oscillation in North America is found to be connected to the AMO, too. — HJS

Geophys. Res. Lett. 28, 2077 (2001).

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