Context:
A groundbreaking study by the Indian Institute of Science (IISc) has made a significant discovery about the Indian monsoon, a phenomenon crucial for the country's agriculture and water supply. The research, published in npj Climate and Atmospheric Science, highlights the critical role of cloud band strength in determining the movement and density of monsoon rain.
Key Findings:
- Cloud Band Strength: The study reveals that the strength of equatorial cloud bands is crucial for their northward movement toward the Indian subcontinent. A robust cloud band enhances atmospheric moisture through intensified winds, facilitating successful northward propagation.
- Impact on Rainfall: Stronger cloud bands contribute to increased rainfall density during monsoon wet spells. This finding challenges previous theories that suggested cloud bands would propagate northward regardless of their initial strength.
- Future Projections: The research indicates that as global temperatures rise, background atmospheric moisture is expected to increase. This change is projected to result in stronger wet spells, with rainfall during these periods expected to escalate by 42% to 63% over India and its adjoining seas.
About Monsoons:
Monsoons are seasonal winds that reverse their direction with the change of seasons. These rhythmic winds are periodic in nature, flowing from the sea to the land during the summer and from land to sea during the winter. The term "monsoon" is derived from the Arabic word mausin or the Malayan word monsin, both meaning 'season'.
Monsoons are a significant climatic feature in the Indian subcontinent. They are more pronounced in this region compared to any other part of the world. The Indian monsoon is a double system of seasonal winds:
- South-West Monsoons: These winds blow from the sea to land during the summer, bringing intense rainfall to most of India.
- North-East Monsoons: These winds blow from land to sea during the winter, bringing rainfall mainly to the southeastern coast of India, such as the southern coast of Andhra Pradesh and Tamil Nadu.
Factors Influencing the Onset of South-West Monsoons
- Heating of the Tibetan Plateau and the high-pressure systems over the Indian Ocean.
- Influence of atmospheric jet streams like the Subtropical Jet Stream (STJ) and the Tropical Easterly Jet (African Easterly Jet).
- The location of the Inter-Tropical Convergence Zone (ITCZ).
Factors Influencing the Intensity of South-West Monsoons
- Strength of the low-pressure system over Tibet and the high-pressure system over the southern Indian Ocean.
- Somali Jet (also known as Findlater Jet) and Somali Current (Findlater Current).
- The Indian Ocean branch of the Walker Cell and the Indian Ocean Dipole.
Conclusion:
The findings of this study will help improve the efficiency of current climate models used to forecast seasonal and sub-seasonal rainfall. Understanding the role of cloud band strength in monsoon rains will enable more accurate predictions, benefiting agriculture, water management, and disaster preparedness.
