National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2005

On the definition of El Niño and associated seasonal average U.S. weather anomalies

Larkin, N.K., and D.E. Harrison

Geophys. Res. Lett., 32(13), L13705, doi: 10.1029/2005GL022738 (2005)

A new NOAA definition of El Niño identifies a number of additional El Niño seasons beyond those conventionally agreed. These additional seasons are characterized by SST anomalies primarily in the western central equatorial Pacific. We show here that the seasonal weather anomalies over the U.S. associated with these additional Dateline El Niño seasons are substantially different from those associated with conventional El Niño seasons. Although some regions have similar associated anomalies, most of the major regional anomalies are quite different. Treating the two as a single phenomenon yields weaker overall seasonal weather associations and does not take advantage of the stronger associations available when the two are treated separately.

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