El Nino (little boy) and La Nina (little girl) in Spanish. These are geographical phenomena that are responsible for variations in temperature and rainfall in the west and east of the pacific ocean.
On an average year in the pacific ocean, Trade winds blow towards the west of the pacific ocean i.e. The Asian continent pushes warm water in the equator towards the Indian Ocean. The warm water in the east pacific is replaced by cold water below the ocean which carries nutrients for phytoplankton. The warm air around the Indonesian region rises and moves towards the south American region where it settles. This is a normal cycle of ocean currents in the pacific ocean called Walker circulation.
What happens during El Nino years is that the Trade winds slow down or may reverse their directions which disrupts the whole process. Now the warm water instead of moving towards the Indian Ocean stays in the Pacific and the water in the Pacific warms up. And the water in the Indian Ocean cools. This phenomenon is called El Nino and occurs typically every two to seven years.
Image Source: climate.gov
La Nina is just the opposite of El Nino, Trade winds this time move faster than normal which warms up the Indian Ocean more than usual, and the east Pacific oceans around the South American region cooler.
How does it affect rain in India?
Monsoon in India is a special weather phenomenon that is directly affected by EL Nino and La Nina years. During El Nino years monsoon rainfall in India is lower than average creating drought-like conditions in some places.
On the other hand, La Niña tends to enhance the strength of the monsoon, resulting in above-normal rainfall.
While these are general tendencies, it’s important to note that the impacts of La Niña and El Niño on the monsoon can vary from year to year and are influenced by other atmospheric and oceanic factors. Therefore, accurate and timely monitoring of these climate phenomena is crucial for predicting and understanding the monsoon behavior in India.