Indian Monsoon: Why Rainfall Increases and Decreases

Indian Monsoon: Why Rainfall Increases and Decreases

Why in News Indian Monsoon: Why Rainfall Increases and Decreases? 

Recently, the India Meteorological Department announced that the country is likely to receive above-normal rainfall in July 2025. The increased rainfall may support crop growth and ease water concerns in several regions.

Indian Monsoon System

• What Is Monsoon?

• • • The monsoon is a seasonal wind pattern that reverses direction due to temperature shifts between land and sea.
    • These winds deliver heavy rainfall across the subcontinent.
    • This pattern defines India’s June–September rainfall season.
    • In summer, land warms up quicker than the ocean, which leads to low-pressure areas forming over the subcontinent.
    • Winds filled with moisture from both the Arabian Sea and Bay of Bengal travel across inland regions during monsoon.

• When Does It Arrive?

• • • The Indian Meteorological Department (IMD) tracks monsoon onset and spread through specific weather markers.
    • It normally reaches Kerala around June 1 and covers the entire country by mid-July. 
    • It withdraws from northwest India by September end.
    • In 2025, the monsoon arrived significantly early in Kerala on May 24, the earliest since 2009.
    • The rain front then swept north and completed its nationwide coverage by June 29—nine days ahead of schedule.

• Importance:

• • Monsoon rains provide nearly 70% of India’s annual precipitation.
  • Farmers begin planting kharif crops—such as rice, maize, cotton, and soy—soon after onset. Timely monsoon supports livelihoods for nearly 45% of India’s workforce.
  • Monsoon replenishes reservoirs, aquifers, and groundwater tables. Around two-thirds of India’s farmland relies solely on monsoon rainfall for irrigation.
  • A healthy monsoon supports rural demand and lowers inflation through good crop output.

Factors Responsible for Increased Rainfall in India

• Indian Ocean Dipole (IOD): The Indian Ocean Dipole is a weather phenomenon observed in the Indian Ocean. When the western Indian Ocean becomes warmer than the eastern part, it creates a positive IOD phase. This phase strengthens the monsoon winds and brings more moisture over India.

• In years like 2019 and 2022, positive IOD helped deliver excess rainfall during monsoon months.

• La Niña Conditions: La Niña brings cooler temperatures to the central and eastern Pacific Ocean and often supports stronger monsoon winds. This cooling strengthens trade winds and supports the southwest monsoon’s strength in India. The stronger winds push more clouds towards the subcontinent, increasing rainfall frequency. La Niña also helps in forming low-pressure areas over the Bay of Bengal.
  • During La Niña years like 2020 and 2021, India recorded above-normal rainfall across most states.
• Low-Pressure Systems: Low-pressure systems often form over the Bay of Bengal during the monsoon season. These systems attract moisture-rich winds that lead to widespread rain. Each depression or cyclone can deliver heavy rainfall over large areas. The frequency and strength of such systems influence overall rainfall volume.
  • In July 2022, for example, multiple depressions led to prolonged wet spells.
• Western Disturbances: Cold air currents from the Mediterranean, called western disturbances, reach northern India and often mix with monsoon systems. It often triggers intense rainfall events in Delhi, Punjab, and Uttarakhand.
  • Jet streams are fast-moving air currents in the upper atmosphere. Their position guides the path of monsoon winds and rain systems.

Reasons Behind Decline in Rainfall in India

• Impact of El Niño: El Niño happens when the central and eastern Pacific Ocean experiences unusual warming, which can weaken India’s rainfall. This warming weakens the trade winds that push monsoon clouds toward India. El Niño disrupts moisture flow and suppresses low-pressure systems, leading to weaker monsoon phases.
• Dry Westerly Winds: Dry winds from the Arabian Peninsula and western Asia often blow into north and northwest India during monsoon months. These winds reduce humidity and push back moist monsoon currents from the Bay of Bengal. When dry westerlies dominate, they block rainfall and increase heat waves.
• Effect of Deforestation: Deforestation reduces local moisture recycling, which is crucial for cloud formation. Forests help hold water in soil and maintain the microclimate required for rainfall. Concrete-heavy cities trap heat, leading to the formation of urban heat zones that interfere with natural rainfall flow. These regions experience altered wind patterns that disturb natural rainfall cycles.
• Climate Change: Global warming has increased India’s average temperature by over 0.7°C since the early 1900s. This rise in temperature affects ocean circulation, wind flow, and monsoon onset timing. The IMD reports more frequent short and intense rainfall events instead of steady patterns.

Impact of Monsoon Variability on Agriculture and Economy

• Crop Output: In India, nearly 50% of cultivated land depends on rainfall. Monsoon timing and strength have a strong effect on crops like rice, cotton, and pulses, which rely on early sowing. In 2015, a 14% rainfall deficit led to a sharp drop in crop yields. Shortfalls during the sowing period reduce germination and plant survival.
• Rural Incomes: Most of India’s workforce relies on agriculture. When crops fail due to poor rains, farmers lose income and reduce spending. This fall in demand affects small traders, local services, and rural industries. In bad monsoon years, loan defaults rise and rural distress increases.
• Rise in Inflation: Low rainfall reduces the supply of cereals, vegetables, and pulses. As production drops, food prices rise in both rural and urban markets. In 2019, erratic monsoon rains led to price spikes in onions and pulses. Inflation caused by poor harvests affects household budgets across all income groups.
• Water Resources: Monsoon replenishes rivers, dams, and groundwater that supply irrigation. When rainfall falls below normal levels, it causes shortages in water used for farming, drinking, and power supply. States like Maharashtra and Karnataka have faced droughts due to back-to-back monsoon failures. Water stress hits cities and villages alike, affecting daily life and productivity.

Government Response and Scientific Monitoring of Monsoon in India

• Role of IMD: The IMD uses advanced forecast models to predict when monsoon will start, how it will spread, and how intense it will be.

• Since 2018, IMD has improved its prediction accuracy with models like the Monsoon Mission.

• The department also gives district-wise weather alerts through SMS and mobile apps.

• Radar Technology: India operates weather satellites like INSAT-3D, INSAT-3DR, and Megha-Tropiques. These satellites monitor cloud formation, wind patterns, and sea surface temperatures. They give real-time data to track rain systems and storm activity.

• The country also uses Doppler Weather Radars (DWRs) to observe local rain movements.

• As of 2024, India had over 35 DWR stations across high-risk areas.

• Government Plans: The government runs programs like PMFBY (crop insurance) to protect farmers from rain damage. Schemes like PMKSY promote micro-irrigation to reduce dependence on rainfall.

• NITI Aayog coordinates state-level water conservation strategies for dry zones.

• Central and state relief funds help drought-affected farmers with compensation.In 2025, the Ministry of Agriculture reviewed rain forecasts to plan seed distribution.