Rainfall recorded in August lowest in 12 years: IMD

Rainfall recorded in August lowest in 12 years: IMD

Part of: Prelims and GS – I – Geography and GS III – Climate change 

Context According to the India Meteorological Department (IMD),

Rainfall in August, which recorded 24% deficiency, was lowest in 12 years.

• The Southwest Monsoon season officially commences from June 1 and lasts till September 30.

What are the possible reasons for large deficient rainfall?

• The formation of less number of low pressure systems (LPS) and their lesser number of days compared to climatology.
• Absence of longer westward movements of LPS during the month of August 2021. 
• Negative Indian Ocean Dipole (IOD) over tropical Indian Ocean, unfavourable for Indian monsoon prevailed throughout the month of August. 

What is the Indian Ocean Dipole? 

• The Indian Ocean Dipole (IOD), also known as the Indian Niño, is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer (positive phase) and then colder (negative phase) than the eastern part of the ocean.
• A negative IOD is associated with the heating of waters of the Indian Ocean.
• A positive IOD is associated with droughts in Southeast Asia and Australia.
• It is expected that the Western Indian ocean will warm at accelerated rates due to climate change leading to an increasing occurrence of positive IODs.
• This is likely to result in the increasing intensity of rainfall during the short rain period over East Africa.