• La Niña
    La Niña is associated with rainy weather in Australia and Indonesia, and cooler sea-surface temperatures off the coast of South America.

    Photograph courtesy NOAA Environmental Visualization Laboratory

    Kicking Up Dust
    The impacts of La Niña on our weather and climate have been highly variable throughout history. La Niña delivers drier, warmer, and sunnier weather along the southern tier of the United States, from California to Florida. This weather increases the risk of wildfires in Florida and dryness in the North American plains. The great Dust Bowl drought of the 1930s is thought to have been caused by a decade of La Niña-like conditions and was likely responsible, in part, for the severe drought in the American Midwest in 1988. The 1988-89 La Niña, believed to be one of the most severe in history, has been estimated to cost $40 billion in damages in North America!

    La Niña is a climate pattern that describes the cooling of surface ocean waters along the tropical west coast of South America. La Nina is considered to be the counterpart to El Nino, which is characterized by unusually warm ocean temperatures in the equatorial region of the Pacific Ocean. 
     
    Together, La Niña and El Niño are the "cold" (La Niña) and "warm" (El Niño) phases of the El Nino-Southern Oscillation (ENSO). ENSO is series of linked weather- and ocean-related phenomena. Besides unusually warm or cool sea-surface temperatures, ENSO is also characterized by changes in atmospheric pressure.
     
    La Niña events sometimes follow El Niño events, which occur at irregular intervals of about two to seven years. The local effects on weather caused by La Niña ("little girl" in Spanish) are generally the opposite of those associated with El Niño ("little boy" in Spanish). For this reason, La Niña is also called anti-El Niño and El Viejo (the old man in Spanish). 
     
    Scientists use the Oceanic Nino Index to measure the deviations from normal sea-surface temperatures that El Niño and La Niña produce in the east-central Pacific Ocean. La Niña events are indicated by sea-surface temperature decreases of more than .5 degrees Celsius (.9 degrees Fahrenheit) for at least five successive three-month seasons. 
     
    La Niña is caused by a build-up of cooler-than-normal waters in the tropical Pacific, the area of the Pacific Ocean between the Tropic of Cancer and the Tropic of Capricorn. Unusually strong, eastward-moving trade winds and ocean currents bring this cold water to the surface, a process known as upwelling. 
     
    Upwelling can cause a drastic drop in sea-surface temperature. Coastal sea-surface temperatures near Ecuador and Peru dropped nearly 4 degrees Celsius (7 degrees Fahrenheit) during the 1988-89 La Niña event. 
     
    Effects of La Niña 
     
    Both El Niño and La Niña affect patterns of rainfall, atmospheric pressure, and global atmospheric circulation. Atmospheric circulation is the large-scale movement of air that, together with ocean currents, distributes thermal energy on the surface of the Earth. These changes are the main sources of variability in climate for many areas worldwide. 
     
    La Niña is characterized by lower-than-normal air pressure over the western Pacific. These low-pressure zones contribute to increased rainfall. 
     
    Rainfall associated with the summer monsoon in Southeast Asia tends to be greater than normal, especially in northwest India and Bangladesh. This generally benefits the Indian economy, which depends on the monsoon for agriculture and industry.
     
    However, strong La Niña events are associated with catastrophic floods in northern Australia. The 2010 La Niña event correlates with one of the worst floods in the history of Queensland, Australia. More than 10,000 people were forced to evacuate, and damage from the disaster was estimated at more than $2 billion.
     
    La Niña events are also associated with rainier-than-normal conditions are over southeastern Africa and northern Brazil. 
     
    La Niña is also characterized by higher-than-normal pressure over the central and eastern Pacific. This results in decreased cloud production and rainfall in that region. Drier-than-normal conditions are observed along the west coast of tropical South America, the Gulf Coast of the United States, and the pampas region of southern South America.
     
    La Niña usually has a positive impact on the fishing industry of western South America. Upwelling brings cold, nutrient-rich waters to the surface. Nutrients include plankton eaten by fish and crustaceans. Higher-level predators, including high-value fish species such as sea bass, prey on the crustaceans. 
     
    La Niña events may last between one and three years, unlike El Niño, which usually lasts no more than a year. Both phenomena tend to peak during the Northern Hemisphere winter. 
     
    Monitoring La Niña
     
    Scientists collect data about El Niño and La Niña using a number of technologies. The National Oceanic and Atmospheric Administration (NOAA), for instance, operates a network of buoys which measure sea-surface temperature, air temperature, currents, winds, and humidity. The buoys are located in about 70 locations, from the Galapagos Islands to Australia. These buoys transmit data to researchers and meteorologists every day.
     
    Using buoy data in conjunction with visual information they receive from satellites, scientists are able to more accurately predict ENSO and visualize its development and impact around the globe.
  • Term Part of Speech Definition Encyclopedic Entry
    abundant Adjective

    in large amounts.

    agriculture Noun

    the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

    Encyclopedic Entry: agriculture
    atmospheric circulation Noun

    large-scale movement of air that helps distribute thermal energy (heat) on the surface of the Earth.

    atmospheric pressure Noun

    force per unit area exerted by the mass of the atmosphere as gravity pulls it to Earth.

    Encyclopedic Entry: atmospheric pressure
    buoy Noun

    floating object anchored to the bottom of a body of water. Buoys are often equipped with signals.

    catastrophic Adjective

    very bad.

    characterize Verb

    to describe the characteristics of something.

    climate Noun

    all weather conditions for a given location over a period of time.

    Encyclopedic Entry: climate
    cloud Noun

    visible mass of tiny water droplets or ice crystals in Earth's atmosphere.

    Encyclopedic Entry: cloud
    conjunction Noun

    combination of items, events, or ideas.

    correlate Verb

    to bring different sets of data into order, or establish a relationship or connection between them.

    crustacean Noun

    type of animal (an arthropod) with a hard shell and segmented body that usually lives in the water.

    current Noun

    steady, predictable flow of fluid within a larger body of that fluid.

    Encyclopedic Entry: current
    data Plural Noun

    (singular: datum) information collected during a scientific study.

    drastic Adjective

    severe or extreme.

    economy Noun

    system of production, distribution, and consumption of goods and services.

    El Nino Noun

    irregular, recurring weather system that features a warm, eastern-flowing ocean current in the eastern Pacific Ocean.

    Encyclopedic Entry: El Niño
    El Nino-Southern Oscillation (ENSO) Noun

    climate pattern in which coastal waters become warmer in the eastern tropical Pacific (El Nio), and atmospheric pressure decreases at the ocean surface in the western tropical Pacific (Southern Oscillation).

    equatorial Adjective

    having to do with the equator or the area around the equator.

    evacuate Verb

    to leave or remove from a dangerous place.

    flood Noun

    overflow of a body of water onto land.

    Encyclopedic Entry: flood
    humidity Noun

    amount of water vapor in the air.

    Encyclopedic Entry: humidity
    indicate Verb

    to display or show.

    industry Noun

    activity that produces goods and services.

    La Nina Noun

    weather system that includes cool ocean temperatures in the eastern Pacific Ocean.

    Encyclopedic Entry: La Niña
    meteorologist Noun

    person who studies patterns and changes in Earth's atmosphere.

    monsoon Noun

    seasonal change in the direction of the prevailing winds of a region. Monsoon usually refers to the winds of the Indian Ocean and South Asia, which often bring heavy rains.

    Encyclopedic Entry: monsoon
    National Oceanic and Atmospheric Administration (NOAA) Noun

    U.S. Department of Commerce agency whose mission is to "understand and predict changes in climate, weather, oceans, and coasts; to share that knowledge and information with others, and; to conserve and manage coastal and marine ecosystems and resources."

    nutrient Noun

    substance an organism needs for energy, growth, and life.

    Encyclopedic Entry: nutrient
    Oceanic Nino Index Noun

    set of data used by scientists to measure the differences in normal sea surface temperatures.

    Pampas Noun

    flat grasslands of South America.

    phenomena Plural Noun

    (singular: phenomenon) any observable occurrence or feature.

    plankton Plural Noun

    (singular: plankton) microscopic aquatic organisms.

    predator Noun

    animal that hunts other animals for food.

    satellite Noun

    object that orbits around something else. Satellites can be natural, like moons, or made by people.

    temperature Noun

    degree of hotness or coldness measured by a thermometer with a numerical scale.

    Encyclopedic Entry: temperature
    thermal energy Noun

    heat, measured in joules or calories.

    trade wind Noun

    winds that blow toward the Equator, from northeast to southwest in the Northern Hemisphere and from southeast to northwest in the Southern Hemisphere.

    transmit Verb

    to pass along information or communicate.

    tropical Adjective

    existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.

    upwelling Noun

    process by which currents bring cold, nutrient-rich water to the ocean surface.

    Encyclopedic Entry: upwelling
    weather Noun

    state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.

    Encyclopedic Entry: weather
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