El Niño is a phenomenon of the catastrophic increase of surface temperature in the eastern part of the Pacific Ocean. It has a significant impact to weather of the American continent and western regions of the tropical Pacific, as well as on the weather and climate of entirely the Earth. Most important factors influencing El Niño are the wind, ocean currents and slope of the water surface (and temperature resulting from these factors) at the equator in the Pacific Ocean. The paper considers results of mathematical modeling of the equatorial Pacific Ocean currents in the El Niño and La Niña phases using the theory of mesoscale turbulence. This theory has been successfully tested in modeling of global circulation of atmosphere and ocean (Arsen’yev et al., 2010) and it has been able to calculate the ocean current changes at equator under changing external conditions. It is shown that the water currents at the equator have a four-tier vertical structure. The surface trade-wind current is located above the subsurface undercurrent, below which we observe the intermediate current, turning into the equatorial deep counter flow. When El Niño begins, the currents are rearranged, change signs and sometimes merge with each other. In the phase of maximum development of the phenomenon there is a two-tier structure: (1) surface current heading the American coast is underlain (below the depth of 440 m) by (2) deep equatorial current directed to the Indonesian coast. The theoretical calculations are compared with the physical observations of ocean currents in the El Niño and La Niña phases. The obtained results indicate that the proposed mathematical apparatus makes it possible to explain the set of physical observations in the Pacific Ocean.

厄尔尼诺现象是太平洋东部表面温度急剧上升的现象。它对美洲大陆和热带太平洋西部地区的天气以及整个地球的天气和气候都具有重大影响。影响厄尔尼诺现象的最重要因素是太平洋赤道处的风，洋流和水面的坡度（以及由这些因素引起的温度）。本文考虑了使用中尺度湍流理论对厄尔尼诺和拉尼娜阶段赤道太平洋洋流进行数学建模的结果。该理论已成功用于大气和海洋全球环流建模的测试（Arsen'yev等，2010年），它能够计算出外部条件变化时赤道的洋流变化。结果表明，赤道处的水流具有四层垂直结构。地表贸易风电流位于地下暗流之上，在该地下暗流之下，我们观察到中间电流，变成赤道深逆流。厄尔尼诺现象开始时，电流会重新排列，改变符号，有时会彼此融合。在该现象的最大发展阶段，存在两层结构：（1）朝向美国海岸的地表水流位于440 m深度以下（低于440 m），是（2）流向印尼海岸的赤道深水流。将理论计算与厄尔尼诺和拉尼娜阶段的洋流物理观测结果进行了比较。