Brief Context
In Context As per the IMD, there are chances of early onset of the southwest monsoon. The normal onset date of the monsoon over Kerala is June 1 and it usually takes about 10 days for the system to reach Kerala from the Nicobar islands. Mechanism of the Indian Monsoon: The Driving Forces Differential Heating of Land and Sea: In summer, India’s landmass heats faster than the ocean, creating low pressure over land and drawing in moisture-laden winds from the sea.
Source Content
Syllabus: GSI/ Indian Physical Geography
In Context
- As per the IMD, there are chances of early onset of the southwest monsoon. The normal onset date of the monsoon over Kerala is June 1 and it usually takes about 10 days for the system to reach Kerala from the Nicobar islands.
Mechanism of the Indian Monsoon: The Driving Forces
- Differential Heating of Land and Sea: In summer, India’s landmass heats faster than the ocean, creating low pressure over land and drawing in moisture-laden winds from the sea.
- Inter-Tropical Convergence Zone (ITCZ): The ITCZ, where trade winds meet near the equator, shifts north during summer, intensifying low pressure over the Indo-Gangetic plain and drawing in monsoon winds.
- Tibetan Plateau: Its high elevation heats up, creating an upper-air low-pressure zone that strengthens vertical circulation and attracts monsoon winds.
- Tropical Easterly Jet: Develops during summer, strengthening monsoon trough and rainfall.
- ENSO:
- El Niño: Warms Pacific waters, usually weakening Indian monsoon.
- La Niña: Cools Pacific, often strengthening monsoon.
- Indian Ocean Dipole (IOD):
- Positive IOD: Strengthens monsoon with warm western Indian Ocean.
- Negative IOD: Weakens monsoon.
Onset and Advancement
- Arabian Sea Branch: Hits Kerala around June 1, moves up the west coast, bringing heavy rain to Western Ghats and inland states.
- Bay of Bengal Branch: Reaches Northeast India in early June, then moves westward along the Indo-Gangetic plain. India is usually fully covered by mid-July.
- Retreat of the Monsoon: Retreat begins in October from northwest India. Clear skies and residual moisture cause hot, humid conditions called “October heat.”
- Reversal of wind direction brings rain to the southeastern coast, notably Tamil Nadu and Andhra Pradesh.
Impact of the Monsoon
- Agriculture: Essential for Kharif crops like rice and maize. A good monsoon improves yields; a poor one leads to drought.
- Economy: Monsoon-linked agriculture influences GDP, rural income, and food prices.
- Water Resources and Hydropower: Rains recharge rivers and reservoirs, crucial for drinking water, irrigation, and electricity.
- Environment and Culture: Supports biodiversity and cultural traditions like festivals celebrating rain.
- Disasters: Heavy rains can trigger floods, landslides, and other disasters, especially in vulnerable regions.
Recent Government Initiatives to Improve Monsoon Forecasting
- Monsoon Mission: Launched in 2012 by the Ministry of Earth Sciences it was a major initiative aimed at enhancing the accuracy of monsoon forecasting.
- National Supercomputing Mission: Aimed at enhancing computational infrastructure needed for running high-end dynamical weather models.
- ICAR & IMD Collab: The IMD, in collaboration with the Indian Council of Agricultural Research (ICAR), provides Agromet Advisory Services.
Source: TH