Southern Peninsular India: Sixth Driest October in 123 Years

Context:

The India Meteorological Department (IMD) recent analysis regarding the rainfall patterns in Southern peninsular India, spanning 123 years of records, exposed that the region encountered its sixth driest October in its meteorological history.

Relevance:

GS I: Geography

Dimensions of the Article:

1. Factors Influencing Rainfall Deficiency in Southern Peninsular India
2. Indian Ocean Dipole (IOD)
3. Cyclone Hamoon
4. El Nino

Factors Influencing Rainfall Deficiency in Southern Peninsular India

Confluence of Northeast Monsoon and Cyclone Hamoon:

• The region experienced an abnormally low rainfall of 74.9mm in October due to the confluence of the northeast monsoon with the development of Cyclone Hamoon.
• This coincided with the deviation of moisture away from southern peninsular India, disrupting wind patterns and delaying the onset of the northeast monsoon.

El Nino and Indian Ocean Dipole (IOD):

• The year 2023 is marked by El Nino conditions along with a positive phase of the Indian Ocean Dipole (IOD).
• This climatic combination has led to reduced rainfall in northern Tamil Nadu and neighboring areas.
• Conversely, the southernmost regions of Tamil Nadu and Kerala have received more substantial rainfall during the same period.

Indian Ocean Dipole (IOD)

• The Indian Ocean Dipole (IOD), sometimes referred to as the Indian Nino, is a phenomenon similar to El Nino.
• It occurs in a relatively smaller area of the Indian Ocean, between the Indonesian and Malaysian coastline in the east and the African coastline near Somalia in the west.
• In the IOD, one side of the ocean along the equator becomes warmer than the other.
• A positive IOD occurs when the western side of the Indian Ocean, near the Somalia coast, becomes warmer than the eastern Indian Ocean.
• Conversely, a negative IOD indicates cooler temperatures in the western Indian Ocean.

Negative IOD

• Air circulation in the Indian Ocean basin moves from west to east near the surface and in the opposite direction at the upper levels.
• Warmer waters from the western Pacific cross into the Indian Ocean, causing a slight temperature rise in that region.
• During normal years, this leads to the rising of air and helps maintain the prevailing air circulation.
• In years when the air circulation becomes stronger, more warm surface waters from the African coast are pushed towards the Indonesian islands, resulting in a warmer western Indian Ocean.
• Hotter air rises, reinforcing the cycle of a negative IOD.

Positive IOD

• Air circulation becomes weaker than normal, and in rare cases, it may even reverse direction.
• As a result, the African coast becomes warmer, while the Indonesian coastline experiences cooler temperatures.
• Positive IOD events often occur during El Nino periods, while negative IOD is sometimes associated with La Nina.
• The cooling effect of El Nino on the Pacific side of Indonesia contributes to the development of a positive IOD in the Indian Ocean.

Cyclone Hamoon:

• Cyclone Hamoon, a highly severe tropical cyclone, made landfall in Bangladesh on October 25, 2023.
• This cyclone originated from a low-pressure system situated in the west-central Bay of Bengal.
• The name “Hamoon” for the cyclone was given by Iran and is derived from the Persian word referring to inland desert lakes or marshlands.

El Nino:

• El Nino is a natural climatic phenomenon characterized by periodic warming of surface waters in the equatorial Pacific Ocean.
• The term “El Niño” is of Spanish origin and translates to “Little Boy.”
• El Nino is one of the two phases of the climate pattern known as El Niño-Southern Oscillation (ENSO).
• In the context of India, El Nino tends to suppress monsoon rainfall.

-Source: The Hindu