National Geographic : 2010 Mar
OCEANS A New El Niño It used to be simpler. Whenever the surface waters of the equatorial Pacific turned warmer than normal in summer, climatologists would expect an El Niño year, then forecast when and where droughts, floods, and hurricanes might occur. But that was before a study by Georgia Tech scientists, led by Hye-Mi Kim, deciphered the effects of another pattern in which high temperatures are confined to the central Pacific (below). Now the already difficult field of atmospheric forecasting has become even trickier. Called El Niño Modoki (Japanese for "similar but different"), it joins El Niño and La Niña, a cold-water phenomenon, as major climate swings that emerge every few years. A Modoki cycle trig- gers more landfalling storms in the Gulf of Mexico and the western Caribbean than normal, and more tropical storms and hurricanes in the Atlantic than El Niño does. Another difference: Modoki's precipitation patterns are the reverse of El Niño's---making the American West, for instance, drier rather than wetter. In 2009, despite early signs of a Modoki year, El Niño prevailed, producing the fewest named Atlantic storms since 1997. ---Tom O'Neill MAPS: JEROME N. COOKSON, NG STAFF SOURCES: HYE MI KIM, GEORGIA INSTITUTE OF TECHNOLOGY; NATIONAL CLIMATIC DATA CENTER, NOAA EQUATOR NORTH AMERICA SOUTH AMERICA 1998 LA NIÑA 2004 MODOKI EQUATOR NORTH AMERICA SOUTH AMERICA PACIFIC OCEAN ATLANTIC OCEAN Gulf of Mexico Caribbean Sea EQUATOR NORTH AMERICA SOUTH AMERICA 1997 EL NIÑO Sea-surface temperature departure from average (in degrees Fahrenheit) August-October -6 -3 9 036 STORM CLUES The busiest hurricane seasons in the Atlantic tend to occur during La Niña years, such as 1998. El Niño years, such as 1997, usually have fewer storms. Modoki is a hybrid of sorts: Its warm waters are like El Niño's, but its storm totals are closer to La Niña's. However, in most years none of the three cycles occurs.