Climate Trivia: El Niño Frequency
Much of our weather in the United States depends on what is happening in the tropical Pacific Ocean. During an El Niño event, which is happening now, the eastern tropical Pacific is warmer than average. During La Niña events, the eastern tropical Pacific is cooler than average. While South America’s west coast may seem far away, what happens there has been shown to affect weather throughout the United States. El Niño events mean more winter Nor’easters on America’s East Coast. El Niño events also result in a more southerly winter storm track, which means more rain and snow for the Southwest but less for the Pacific Northwest. Hurricane season in the Atlantic is less active during El Niño phases and more active during La Niña phases. An intermediate stage, known as the neutral phase, means more snowfall throughout the Mississippi River basin.
Trivia Question: What phase has been more common over the last 25 years?
a) El Niño
b) La Niña
The correct answer is a. El Niño events have become more common since the mid-1970′s. Duing the 1950′s and 1960′s, La Niña events were more common. See below for a graph of the last 60 years of El Niño (red) and La Niña (blue) event frequency.
Seasons: Winter, Spring, Summer, Fall
Sources: Kim, HM et al. “Impact of Shifting Patterns of Pacific Ocean Warming on North Atlantic Tropical Cyclones.” Science 325 (2009): 77-80 and Twine, TE et al. “Effects of El Niño-Southern Oscillation on the Climate, Water Balance, and Streamflow of the Mississippi River Basin.” Journal of Climate 18 (2005): 4840-4861 and Meehl, GA et al. “Current and Future U.S. Weather Extremes and El Niño.” Geophysical Research Letter 34 (2007) L20704 and Easterling, David. “Observed Climate Variability and Change.” NOAA/National Climatic Data Center. Ashville, NC: 31 January 2007 http://www.ametsoc.org/atmospolicy/documents/Easterling-Observed-Change-Jan-07.pdf and Meehl, GA et al. “Current and Future U.S. Weather Extremes and El Niño.” Geophysical Research Letter 34 (2007) L20704 and Easterling, David. “Observed Climate Variability and Change.” NOAA/National Climatic Data Center. Ashville, NC: 31 January 2007 http://www.ametsoc.org/atmospolicy/documents/Easterling-Observed-Change-Jan-07.pdf.
