The India Meteorological Department (IMD) has recently published an analysis of rainfall patterns in Southern peninsular India, based on records spanning 123 years. It reveals that this region experienced its sixth driest October ever recorded. The Southern Peninsular area, which includes Kerala, Mahe, South Interior Karnataka, Tamil Nadu, Karaikal, Puducherry, coastal Andhra Pradesh, Yanam, and Rayalaseema, only received about 74.9mm of rain in October, marking a 60% decline from the norm.
Key Factors Contributing to Rainfall Deficiency
The deficiency in rainfall was influenced by several key factors, including the confluence of the Northeast Monsoon and Cyclone Hamoon, the effects of El Nino year and the Indian Ocean Dipole (IOD), among others.
The Impact of Northeast Monsoon and Cyclone Hamoon
The timing of Cyclone Hamoon’s emergence coincided with the onset of the northeast monsoon, leading to a diversion of moisture away from southern peninsular India. This shift altered wind flow patterns and weakened the onset of the monsoon.
The Role of El Nino and the Indian Ocean Dipole (IOD)
2023 was marked as an El Nino year with a positive phase of the Indian Ocean Dipole (IOD). Under these conditions, areas such as northern Tamil Nadu experienced less rainfall while southernmost parts of Tamil Nadu and Kerala received adequate rainfall in October.
Details on Cyclone Hamoon
Cyclone Hamoon was a severe tropical cyclone that made landfall in Bangladesh on October 25, 2023. Originating as a low-pressure area over the west-central Bay of Bengal, it was named by Iran. The term “Hamoon” is a Persian word referring to inland desert lakes or marshlands.
El Nino Phenomenon
El Nino is characterized by a periodic warming of surface waters in the equatorial Pacific Ocean. This natural phenomenon suppresses the monsoon rainfall in India and affects global weather patterns.
The Indian Ocean Dipole (IOD) Effect
The IOD is an atmosphere-ocean phenomenon in the Indian Ocean, which is distinguished by a disparity in sea surface temperatures between the eastern and western Indian Oceans.
About The India Meteorological Department
Established in 1875, the IMD is the country’s National Meteorological Service and the main government agency responsible for all matters related to meteorology and associated subjects.
UPSC Civil Services Examination Question on IOD
In the 2017 UPSC Civil Services examination, there was a question on the Indian Ocean Dipole (IOD) in relation to forecasting the Indian monsoon. The question was as follows:
“With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting the Indian monsoon, which of the following statements is/are correct?
1. IOD phenomenon is characterized by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.
Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2”
The correct answer to this question was option (b).