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El Nino

El Nino


     El Nino is a phenomena that Sea Surface Temperature (SST) in the tropical Pacific is warmer than normal state. The period of El Nino is irregular, changes 2-7 years. The warm event affects not only over the tropical Pacific region happening El Nino but also over global region by the changes of atmospheric circulation. Recently, it has been appreciated the importance for study of El Nino as it is known that El Nino cause unusual change in the weather. CDL (Climate Dynamics Laboratory) study on dynamics and impacts of El Nino and develop coupled model which forecast El Nino.


1. The Basics

     

    - What is El-Nino?

     

             a) The Definition of El-Nino

    : The definition of El Nino make a slightly difference by scientists. In general, however, El Nino is defined the period that the time, SST Anomaly in the Equatorial eastern Pacific (Nino3 Index or Nino3.4 Index) is greater than 0.5C, last 5 months.

    b) What is La Nina?

    La Nina is characterized by unusually cold ocean temperatures in the Equatorial eastern Pacific. El Nino and La Nina are not independent events but opposite phases of the El Nino-Southern Oscillation (ENSO) cycle, with La Nina sometimes referred to as the cold phase of ENSO and El Nino as the warm phase of ENSO.

    c) Southern Oscillation?

    El Nino results from interaction between the surface layers of the ocean and the overlying atmosphere in tropical Pacific. Southern Oscillation is the seasaw oscillation of Sea level pressure in the tropics. SST warming is oceanic response, Southern Oscillation is atmospheric response by SST change associated with El Nino and La Nina. Therefore El Nino and Southern Oscillation (ENSO) is coupled mode of atmosphere and ocean system.

    d) The Origin of the Name, El Nino

    El Nino were originally recognized by fisherman off the coast of South America as the appearance of unusually warm water in the Pacific ocean. El Nino means The Little One in Spanish. This name was used often the tendency of the phenomenon to arrive around Christmas.

    e) How often does El Nino occur?

     

    El Nino's usually occur irregularly, approximately every two to seven years. The El Nino years 1976-1977, 1982-1983, 1986-1987, 1991-1994 and 1997-1998 are distinguished by large SST anomalies. The first half of the 1990's is unusual in that the past four years have all been unusually warm in the equatorial Pacific. El Nino typically last 12-18 months.

    - The global impacts of El-Nino


    The twists and turns in the interaction between ocean and atmosphere in the Pacific can have a ripple effect on climatic conditions in global region.

    With El Nino, the period October through March tends to be wetter than usual in a swath extending from southern California eastward across Arizona, southern Nevada and Utah, New Mexico, and into Texas. There are more rainy days, and there is more rain per rainy day. El Nino winters can be two to three times wetter than La Nina winters in this region.

    In the Pacific Northwest, El Nino tends to bring drier winters. The area affected in this manner includes Washington, Oregon, and the more mountainous portions of Idaho, western Montana and northwest Wyoming. This area of influence extends well up into Canada, and coincides very well with the Columbia River Basin on both sides of the U.S./Canada border.

    Winter temperatures with El Nino conditions tend to be warmer than usual from Washington and northern Oregon across the northern tier to Montana, also along the West Coast and East Asia.

    In general, in all these regions, La Nina climate effects are approximately, but not exactly, opposite to El Nino climate effects.

     

    - Impacts of El-Nino on Korea

     

  Figure shows the relation of El-Nino and temperature in korea. Marked E in figures appears the period of El-Nino. In El-Nino summer, temperature in korea is mostly cool than normal temperature of summer. Only one case of warm events is warmer than normal in summer. The case of winter, the temperature during El-Nino period tend to be warmer than normal. For 15 warm events, only two case was cold, the others are normal or warm. The relation of El-Nino and precipitation in Korea is not significant, compared to the temperature relation, but precipitation in summer tend to increase than normal value during El-Nino period.

 Temperature and Precipitation in Korea during El-Nino period

 

Winter

Summer

Temperature

warm

cold

Precipitation

 

wet

 

    

  El-Nino effects on typhoon which caused extensive damage. Figure shows generating points of Typhoon which passed into Korea. During El-Nino period, generation region of Typhoon located in the south compared to non El-Nino period. It is reason that convergence structure in the tropics is changed by El-Nino. The moving path of the typhoon is more long and regular. It can be understand that the change of the North Pacific high effects on the moving path.

       

 


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