Why has the monsoon come early this year?, Pg10

Key Highlights:

• Southwest monsoon arrived in Kerala on May 24, a week earlier than usual; earliest onset since May 23, 2009.
• Since 1970s, data suggests systematic delay in monsoon onset by a few days.
• Early onset does not guarantee above-normal rainfall; historical data (2009) shows early onset can still result in drought.
• Current onset coincides with neutral ENSO conditions, but there are hints of El Niño development later in the year.
• Monsoon trough and low-pressure systems around Bay of Bengal and Arabian Sea influence Kerala onset.
• Local factors like land-sea temperature contrast, jet stream shifts, and tropical Pacific SSTs contribute to variability.
• Early rainfall observed along west coast and northeastern states in recent weeks.

Detailed Insights:

• The science behind monsoon onset remains inexact, and predicting exact arrival is still a forecasting challenge.
• While ENSO (El Niño-Southern Oscillation) conditions heavily influence monsoon behaviour, other factors like MJO (Madden–Julian Oscillation), ITCZ shifts, and western disturbances also play roles.
• Current patterns suggest a strong pressure gradient over the Arabian Sea, favouring low-level monsoon winds toward Kerala.
• There is also a decline in pre-monsoon rainfall and warming in the Indian Ocean, both altering monsoon dynamics.

Scientific/Technical Concepts Involved:

• El Niño & La Niña: Ocean-atmospheric phenomena involving Pacific Ocean SST anomalies. El Niño often weakens Indian monsoon, while La Niña strengthens it.
• Monsoon Onset: Defined by parameters like wind direction, cloud cover, pressure patterns, and rainfall thresholds over Kerala.
• Madden–Julian Oscillation (MJO): A major intra-seasonal atmospheric fluctuation influencing monsoon bursts and dry spells.
• Indian Ocean Dipole (IOD): An SST gradient in the Indian Ocean that can modulate monsoon strength.

Significance:

• Early monsoon impacts agriculture planning, reservoir levels, and disaster preparedness across India.
• Understanding monsoon onset is critical in the context of climate change, which is altering seasonal rainfall distribution and making weather events more unpredictable.
• This knowledge aids in forecasting flood and drought risks, crucial for food security and economic stability in India.

Mains Mock Question:

What are the major factors influencing the onset of the Indian monsoon? Discuss how variability in monsoon timing can affect India’s agriculture and water resource planning.