El Niño

• In normal years, winds in the Pacific circulate around a cell. What is this cell known as?

  The Walker cell
• In normal years, winds travel west and take warm surface water with them. It rises over Indonesia, creating low pressure and heavy rain
• In normal years, the rising air above Indonesia begins to travel east again in the upper atmosphere. It reaches South America and sinks as cool air to give dry desert conditions
• During an El Niño year, the cell reverses and trade winds move east instead, taking warm surface water to South America and cold atmosphere air to Indonesia
• El Niño effect on South America

  Heavy rainfall along the coast, from California down to Peru
• El Niño effect on South East Asia

  Large drought in Australia and the rest of SE Asia, severe tropical storms in Japan
• How often does El Niño occur?

  Roughly every 7 years
• Sometimes, we reach La Niña instead of El Niño. What is La Niña?

  Extreme normal - opposite of El Niño. This means very dry South America and lots of rainfall in Australia