The weather-altering phenomenon unveiled!
El Nino phenomenon is the presence of warm surface water along the western coasts of South America (especially Peru), due to an altering of normal winds in the southern hemisphere. In an El Nino year, the trade winds that blow towards Australia either greatly reduce, die completely, or in extreme years even reverse. This stops the ocean current from pushing warm water towards Australia, and instead the higher waters on the Australian coast ebb back towards Peru. This increases both the sea temperature and level on the South American coast. The changes in the area also mean that the convectional uplift and resulting rainfall which normally occurs in Australia moves to the Peruvian coast.
Scientists still struggle to fully understand El Nino, when it is coming and why it occurs. Each one is different and how the atmosphere reacts each time varies. Due to these varying conditions and irregularity, the cause of El Nino is not completely understood. While we know it is caused by wind change, little more is certain.
El Nino phenomenon occurs roughly every four to seven years and lasts on average between 12 and 18 months. However, in recent years it appears to be increasing in regularity.
Closely linked with the El Nino phenomenon is that of La Nina. In La Nina years normal conditions of the Pacific are heightened, due to extra strong trade winds. This means the waters of Peru are much colder than normal, and the convectional rain of eastern Australia is heavier.
Conditions during El Nino phenomenon
• Weaker or even reversed trade winds
• Warmer seawater in western South America
• Higher sea level on the Peruvian coast
• More rainfall in South America
• Drier conditions in Australia