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What is La Niña? |
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La Niña Information |
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La Niña in the News |
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Impacts for the U.S. |
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Impacts Worldwide |
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About SW Climate:
La
Niña Overview
In the most basic sense, La Niña can be described as a change in the surface temperature of the equatorial Pacific Ocean, which typically results in a near global shift in precipitation patterns. La Niñas are characterized by anomalously cool sea surface temperatures (SSTs) in the equatorial eastern Pacific Ocean. This effect is most evident in the Northern Hemisphere winter season (December to March). La Niña and El Niño are both components of the naturally occurring climate cycle known as El Niño/Southern Oscillation (ENSO). Climate conditions associated with a typical La Niña may last for nine to twelve months with some La Niña episodes persisting for up to two years.
Changes in atmospheric pressure prompt the ocean/atmosphere interactions that lead to La Niñas. Though La Niña-influenced impacts vary widely in timing and extent, La Niñas tend to enhance the "normal" climate of any given part of the world. Regions that are typically rainy may experience even more rain than usual while areas that are typically dry may experience periods of drought. Tucson, Arizona, for example, often becomes warmer and drier during La Niña events while Seattle, Washington, can see periods that are cooler and wetter.
La Niņa, The North American Monsoon, and Experimental Products
University of Arizona paleoclimate research derived from coral bands shows that some of the most severe droughts in United States since 1700 have coincided with prolonged La Niņa conditions in the Pacific Ocean.
The North American Monsoon is the result of a complicated set of interactions between thermally driven air circulation and the extremely varied topography in the monsoon region.
Experimental Applied Climate Information System (ACIS) Maps
ACIS is a web-based application that summarizes climate information in map format over a variety of user-chosen timescales and geographic areas.
Experimental Drought Blend Maps
Drought blend maps mathematically combine drought monitoring tools such as the Palmer drought index and precipitation to create national maps of both short-term and long-term drought.
Download these four figures in one PDF [pdf 1.57 mb]
Headlines from the 1999 La Niña period
Drought
Hot, dry weather caps a decade of extremes (The Christian Science Monitor, July 8, 1999)
Drought affecting most state's lakes (The Arizona Republic, July 3, 1999)
A drought emergency is declared in Arizona (The New York Times, June 27, 1999)
Ranchers bracing themselves as state hopes for aid, rain (The Arizona Republic, June 27, 1999)
Hull seeks federal aid for drought: Emergency declared to assist ranchers (The Arizona Republic, June 24, 1999)
Drought knows no borders: Hermosillo pins hope for rain on prayers (The Arizona Daily Star, March 22, 1999
Water Shortage
Test the waters: A few lakes in highlands achieve high marks for solitude (The Arizona Republic, June 20, 1999)
Control developers to save water (The Arizona Republic, May 29, 1999)
Storms "too little, too late": Moisture won't do much for fire danger, lake levels (The Arizona Republic, April 6, 1999)
Excessive watering now could force summer ban (The Arizona Daily Star, March 4, 1999)
Wildfires
Be aware of fire restrictions (The Arizona Republic, June 27, 1999)
Wildfire fears spread as the nation Drs out (The Detroit News, April 25, 1999)
Girding for wildfires: A dry winter sets scene for a hot season (The Arizona Daily Star, March 24, 1999)
Storm little help to dry state: Snow, rain amounts too small to ease wildfire threat (The Arizona Republic, March 17, 1999)
Get ready for drought effects (The Arizona Republic, March 14, 1999)
High & dry: La Niña raises threat of fire in Arizona forests (The Arizona Republic, March 3, 1999)
Wildfire season starts a bit early (The Arizona Daily Star, February 27, 1999)
Wildfire danger worst in 60 years: Forest officials seek federal help (Southern Arizona Online)
Wildlife
Both good and bad news for hunters this season (The Arizona Daily Star, April 8, 1999)
Drought wreaking havoc with deer: Hunts to aid in control of population (The Arizona Republic, April 1, 1999)
El Niño gives, La Niña takes: Bear cubs face death in drought (The Arizona Republic, March 18, 1999)
Pools, fountains are magnets for thirsty wildlife (The Arizona Daily Star, March 22, 1999)
La Niña Impacts - United States
Climate Prediction Center reports
U.S. seasonal precipitation impacts
U.S. seasonal temperature impacts
Selected U.S. La Niña winter impacts for temperature and precipitation
Climate Impacts Group: University of Washington
ENSO and the Pacific Northwest
Climate Prediction Center
National Geographic Magazine
Check out "El Niño/La Niña" from the March 1999 issue
The CLIMAS Links Database includes links
to information about both El
Niño and La Niña.