The current deficiency in rainfall over the southern peninsular region of India has indicated that the northeast monsoon remains subdued this year. This development is vital news as the region relies heavily on the rainy season for various activities.
Understanding India’s Rainfall Pattern
India experiences rainfall during two main seasons annually. Approximately 75% of the country’s annual rainfall occurs from the Southwest monsoon that spans from June to September. The Northeast monsoon, also known as the winter monsoon, happens from October to December.
Compared to the former, the Northeast monsoon is a relatively smaller scale monsoon that restricts itself to the Southern peninsula of India. By mid-October, following the complete withdrawal of the Southwest monsoon, there is a rapid shift in the wind pattern from south-westerly to north-easterly direction.
The Significance of the Northeast Monsoon and Rainfall
The period following the Southwest monsoon, from October to December, marks the highpoint of cyclonic activity in the North Indian Ocean region. This region covers the Arabian Sea and the Bay of Bengal. The winds tied to the formation of low pressure systems, depressions, or cyclones heavily influence the Northeast monsoon, ultimately affecting the overall rainfall.
Various regions in India depend on the Northeast monsoon for rainfall. These regions include Tamil Nadu, Puducherry, Karaikal, Yanam, coastal Andhra Pradesh, Kerala, north interior Karnataka, Mahe, and Lakshadweep. Particularly in Tamil Nadu, about 48% of the annual rainfall happens during these months, making it crucial for agricultural activities and reservoir management. Some South Asian countries like Maldives, Sri Lanka, and Myanmar also receive rainfall during this period.
Reasons Behind Deficient Rainfall During the Current Northeast Monsoon
The prevailing La Niña conditions in the Pacific Ocean is one of the key contributors to the deficient rainfall this Northeast monsoon. Although these conditions enhance the Southwest monsoon’s rainfall, they negatively impact the Northeast monsoon’s rainfall. La Niña refers to the large-scale cooling of ocean surface temperatures in the central and eastern equatorial Pacific Ocean, resulting in changes in tropical atmospheric circulation, including winds, pressure, and rainfall.
Compared to El Niño — the abnormal surface warming observed along the Pacific Ocean’s eastern and central regions — La Niña leads to opposite impacts on weather and climate. Both La Niña and El Niño are large-scale ocean phenomena that can influence global weather patterns, including wind movements, temperature, and rainfall levels. They can trigger extreme weather events like droughts, floods, and erratic hot and cold conditions across the world.
The Role of Inter Tropical Convective Zone (ITCZ)
The current positioning of the ITCZ has also contributed to the poor rainfall during this monsoon season. The ITCZ is a low-pressure belt that moves along the equator, determining precipitation in the tropics. Currently, it is located north of its usual position.
Other Influential Atmospheric Circulation: Madden-Julian Oscillation (MJO)
The MJO, an eastward moving ‘pulse’ of clouds, rainfall, winds, and pressure near the equator, recurs every 30 to 60 days. It plays a significant role in the atmospheric circulation affecting the monsoon seasons in India.
Last Modified: February 9, 2024