El Nino develops every few years and involves a Pacific Ocean warming of 1 to 2 degrees Celsius, which typically extends from the Peruvian coast to the International Date Line, spanning about 100 degrees of longitude, or onequarter of the earth's surface. This change in sea temperature alters tropical weather patterns, and can influence short-term climate over the globe through changes in atmospheric circulation. El has led to droughts in Australia, Indonesia, the Philippines, northeast Brazil, and southern Africa, while causing excessive rainfall in Peru, Ecuador, and the central Pacific.
Scientists have noted three types of weather anomalies over North America that characteristically accompany an El Nino episode: (1) above- normal rainfall in the southeastern United States and Gulf Coast; (2) above-normal temperatures in the Pacific Northwest, Alaska, and western Canada; and (3) below- normal temperatures in the southeastern United States.
Major El Nino events during the winters of 1940-41, 1982-83, 1992-93 and now 1994-95 have produced exceptionally wet weather in U.S. west coast and southwest states. But during more moderate El Nino events (e.g., the winters of 1986-87, 198788), very dry conditions have been the rule, contributing to the California drought of the late 1980s. During strong El Ninos, sea-surface temperatures and tropical convection increase in the central Pacific Ocean east of the International Date Line, carrying the jet stream in midlatitudes farther east than normal, so that the jet stream and associated storm tracks often extend to California.
Learning to recognize El Nino signals is a special research area at NCAR, as well as at a number of universities throughout the U.S. In-depth information on El Nino is available by contacting the scientists listed below:
Selected El Nino Scientists at NCAR:
Kevin Trenberth (tel. 303-497-1318) and James Hurrell (tel. 303497-1383); Mechanisms and evolution of El Nino events over the past 100 years
Michael Glantz, (tel. 303-497-8119); Societal aspects of El Nino events, including the use of El Nino information in decisionmaking
Gerald Meehl (tel. 303-497-1331); Climate model simulation of El Nino
Selected NSF-funded El Nino Scientists at Other Institutions:
Timothy Barnett (tel. 619-534-3223); Climate Research Group, Scripps Institution of Oceanography, University of California, San Diego; Forecasts of El Nino
Mark Cane (tel. 914-365-8344); Columbia University's Lamont Doherty Earth Observatory, Palisades, New York; Forecasts and modeling of El Nino
James O'Brien (tel. 904-644-4581), Department of Meteorology, Florida State University; Forecasts and modeling of El Nino
Eugene Rasmussen (tel. 301-405-5376), Department of Meteorology, University of Maryland, and the Cooperative Institute for Climate Studies, University of Maryland; Behavior of El Nino
J. Michael Wallace (tel. 206-543-7390), Department of Atmospheric Sciences, University of Washington, Seattle; Analysis of El Nino observations during the last 100 years
J. Shukla (tel. 301-902-1243), IGES, Center for Ocean-Land Atmosphere; El Nino predictability
Peter Webster (tel. 303-492-5882), University of Colorado; El Nino theory and atmospheric dynamics
David Neelin (tel. 310-206-0651), UCLA; Tropical ocean atmosphere coupling and theory
Roger Lukas (tel. 808-956-7896), University of Hawaii; Ocean dynamics and observations