Answer:
La Nina refers to the lowering of the temperature of the ocean surface water of the eastern part of the tropical Pacific region. It is the opposite of El Nino, and the occurrence of this La Nina southern oscillation causes tremendous effect in the global climatic condition.
The process of upwelling takes place, where the ocean currents bring the cold water from the bottom to the ocean surface with the help of the trade winds that blow towards the east.
Due to the occurrence of La Nina, a large amount of rainfall occurs in the Southeastern part of Asia during the time of summer monsoon. Rainfall is maximum in Australia and often leads to flooding. Moreover, the effects are also seen in the northwestern part of India as well as Bangladesh, where a large amount of rainfall takes place.