Long-term temperature runs in the Northeast -- four months or more of higher-than-normal or lower-than-normal readings -- are broken up by El Niño weather events, which begin in the Pacific Ocean, according to a Cornell University climatologist.

"This is just another small piece to fit into making weather forecasts," said Arthur T. DeGaetano, Ph.D., a climatologist with the Northeast Regional Climate Center at Cornell University. DeGaetano presented a paper, "Persistence of Northeastern U.S. Temperature Anomalies in Relation to ENSO (El Niño Southern Oscillation) Occurrence," at the American Meteorological Society's Conference on Climate Variations at Long Beach, Calif., on Feb. 5. The research was supported by the National Oceanic and Atmospheric Administration (NOAA), which oversees the regional climate centers.

"El Niño conditions don't occur all that frequently. But, if there is an El Niño event and if there is a temperature run occurring in the Northeastern U.S., then our statistics show that the El Niño affects the break in the temperature run in most cases," he said.

El Niño is a term to describe a gradual warming of the tropical portions of the Pacific Ocean, causing ocean-atmospheric disturbances that could be responsible for flooding, drought and perhaps even brush fires worldwide. NOAA has deployed a series of buoys throughout the Pacific to transmit water temperature data in real time. When the up-welling of cold water does not occur, the warm water begins to gather, causing an El Niño and thus affecting global weather patterns.

If there is a particularly hot summer or a brutally cold winter, and an El Niño develops in the Pacific, it is quite likely that the temperature run in the Northeast will cease within 90 days of the start of the El Niño, DeGaetano said.

DeGaetano studied a period of 64 years of Northeastern United States weather, from 1931 to 1995, to correlate the high- and low-temperature runs with the 12 El Niño events of the past six decades. If there is a temperature run, it is finished within three months of the start of an El Niño event, his evidence shows.

Other regions of the country more likely to be affected by El Niño events did not show the same pattern as the Northeast. For example, in the Pacific Northwest fewer temperature runs were found to terminate prior to the onset of El Niño. DeGaetano found some evidence that temperature-run lengths increased in the Pacific Northwest and along the Gulf Coast during El Niño events.