The term "monsoon" refers to the climate associated with the seasonal reversal of wind direction. The monsoons are a double system of seasonal winds that travel from the sea to the land in the summer and from the land to the sea in the winter. Monsoons can be found in the Indian subcontinent, central-western Africa, Southeast Asia, and a few other places, but the winds are strongest in the Indian subcontinent. The Indian monsoon is responsible for approximately 70% of India's annual rainfall. This article will explain to you about Indian Monsoon which will be helpful in preparing Geography for the UPSC Civil service exam.

Indian Monsoon

• The climate in India is hot monsoonal, as is the climate in South and Southeast Asia.
• Out of four seasons prevailing in the Indian subcontinent, monsoon seasons acquire two. They are
• The Southwest Monsoon Season
• The North-East Monsoon Season

Onset of the Monsoon

• When the sun shines vertically over the Tropic of Cancer in April and May, the large landmass to the north of the Indian Ocean becomes extremely hot.
• In the northwestern part of the subcontinent, this results in the formation of an intense low-pressure system.
• The low-pressure cell attracts southeast trades across the Equator because the pressure in the Indian Ocean to the south of the landmass is high due to the slow heating of water.
• These conditions aid in the ITCZ northward shift in position.

• After crossing the Equator, the southwest monsoon can be seen as a continuation of the southeast trades deflected towards the Indian subcontinent.
• Between 40°E and 60°E longitudes, these winds cross the Equator.
• The southwest monsoon arrives on the Kerala coast on June 1st and moves quickly through Mumbai and Kolkata between June 10th and 13th.
• The southwest monsoon engulfs the entire subcontinent by mid-July.

The Southwest Monsoon Season

• The Rainy Season is from June to September.
• As a result of the rapid rise in temperature over the northwestern plains in May, the low-pressure conditions there have become even more intense.
• They are powerful enough to attract the Southern Hemisphere trade winds coming from the Indian Ocean by early June.
• These southeast trade winds cross the equator and enter the Bay of Bengal and the Arabian Sea, only to become entangled in the air circulation over India.
• They bring a lot of moisture with them as they pass over the equatorial warm currents.
• They travel in a southwesterly direction after crossing the equator. Southwest monsoons are named after this.

Southwest Monsoon Bursts

• The rain begins abruptly during the southwest monsoon season.
• The first rain has the effect of significantly lowering the temperature.
• The "break" or "burst" of the monsoons refers to the sudden onset of moisture-laden winds accompanied by violent thunder and lightning.
• In the coastal areas of Kerala, Karnataka, Goa, and Maharashtra, the monsoon may arrive in the first week of June, while in the interior, it may arrive in the first week of July.
• Between mid-June and mid-July, the daytime temperature drops by 5°C to 8°C.
• The relief and thermal low pressure over northwest India modify the southwesterly direction of these winds as they approach the land.
• The monsoon is divided into two branches as it approaches the landmass:
• The Arabian Sea branch
• The Bay of Bengal branch

*To know more about this, click Southwest Monsoon Season

North-East Monsoon

• The northeast monsoon enters India from the northeast.
• The wind blows from the sea to the land in this type of monsoon.
• The moisture from the Indian Ocean is carried by the monsoon winds.
• The northeast monsoon is limited to south India, bringing rain to Tamil Nadu, Puducherry, Karaikal, Yanam, Andhra Pradesh, Kerala, Mahe, and south interior Karnataka from October to December.
• Low-pressure systems, depressions, and cyclones cause the associated rainfall, also known as the winter monsoon.
• This is Tamil Nadu's main rainy season, with the state receiving 48% (447.4mm) of its annual rainfall during these three months.

*To know more about this, click North-East Monsoon

Monsoon winds of the Arabian Sea

The three branches of the monsoon winds that originate over the Arabian Sea are as follows:

• The first stream hits India's west coast, dumping over 250 cm of rain on the country.
• It strikes the Western Ghats perpendicularly, resulting in abundant Orographic Rainfall [400 to 500 cm annual rainfall on the windward side].
• On the leeward side of the crest, rainfall is reduced to about 30-50 cm.
• On the immediate leeward side of the Western Ghats, there is a narrow belt of severe aridity.
• However, once it has passed, the air begins to rise again, and rainfall amounts increase further east.
• The second stream flows through the Narmada—Tapi troughs (narrow rift valley) before reaching central India.
• Due to the lack of a major orographic obstacle across the rift, it does not produce much rain near the coast.
• This stream brings rain to some parts of central India (Ex: Nagpur).
• The third stream runs parallel to the Aravali Range and does not produce much rain. As a result, Rajasthan is primarily a desert state.
• On the south-eastern edge of the Aravali Range, however, there is some orographic effect.
• Mt. Abu receives about 170 cm of rain, whereas the surrounding plains receive only 60 to 80 cm.

Monsoon Winds of Bay of Bengal

The monsoon from the Bay of Bengal Branch is divided into two distinct streams:

• The first stream reaches Meghalaya after crossing the Ganga-Brahmaputra delta.
• The orographic effect causes heavy rainfall in this area. Cherrapunji receives 1,102 cm of annual rainfall, the majority of which falls between June and August.
• Mawsynram (the current champion), which is located at 1,329 metres above sea level and is only 16 kilometres west of Cherrapunji (the X champion), receives more annual rainfall (1,221 cm).
• Both stations are at the northern end of a deep valley that runs from south to north on the southern slopes of the Khasi hills.
• The Bay of Bengal branch's second stream flows along the Himalayan foothills, deflected to the west by the Himalaya, bringing widespread rainfall to the Ganga plain.
• As we move from east to west up the plain, the rainfall from this stream decreases steadily.
• The rain shadow effect of the Arabian Sea current and the Bay of Bengal current, which flow parallel to the coast, keeps the Tamil Nadu coast relatively dry during the southwest monsoon season.

Characteristics of Monsoonal Rainfall

• Rainfall from the southwest monsoons follows a seasonal pattern that takes place between June, August, and September.
• Rainfall during the monsoon season is largely determined by relief or topography.
• The windward side of the Western Ghats, for example, receives over 250 cm of rain. The hill ranges and the Eastern Himalayas are once again responsible for the heavy rainfall in the northeastern states.
• With increasing distance from the sea, monsoon rainfall tends to decrease.
• During the southwest monsoon, Kolkata receives 119 cm of rain, Patna 105 cm, Allahabad 76 cm, and Delhi 56 cm.
• Monsoon rains come in short bursts, lasting a few days at a time.
• The wet spells are separated by 'breaks,' which are periods of no rain.
• The cyclonic depressions that form at the head of the Bay of Bengal and cross into the mainland are the cause of these rain breaks.
• Aside from the frequency and intensity of these depressions, the path they take determines the rainfall distribution.
• Summer rainfalls in a torrential downpour, causing significant runoff and soil erosion.
• As the southwest monsoon season receives over three-quarters of the country's total rainfall, monsoons play a critical role in India's agrarian economy.
• It has an uneven spatial distribution, ranging from 12 cm to more than 250 cm.
• The start of the rains can be significantly delayed over the entire country or a portion of it.
• Rains can end much earlier than expected, causing significant damage to standing crops and making winter crop sowing difficult.

Season of Retreating Monsoon

• Monsoons are known to retreat in the months of October and November.
• By the end of September, the southwest monsoon gets weakened as the Ganga plain's low pressure trough begins to move southward in response to the sun's southward march.
• By the first week of September, the monsoon leaves western Rajasthan.
• By the end of the month, it will have left Rajasthan, Gujarat, the Western Ganga plain, and the Central Highlands.

Retreating Monsoon in the Southern Half of India

• The low-pressure system covers northern parts of the Bay of Bengal by early October, and it moves over Karnataka and Tamil Nadu by early November.
• The center of low pressure will be completely removed from the Peninsula by the middle of December.
• Clear skies and rising temperatures signal the retreating of the southwest monsoon season. The ground is still wet.
• The weather becomes oppressive as a result of the high temperature and humidity. This is referred to as the 'October heat.'

Retreating Monsoon in the Northern Half of India

• The temperature begins to drop rapidly in the second half of October, especially in northern India.
• The weather in north India during the retreating monsoon is dry, but rain is associated with it in the eastern part of the Peninsula.
• The rainiest months of the year are October and November in this area.
• The rainy season is linked to the passage of cyclonic depressions that originate over the Andaman Sea and make their way to the southern Peninsula's eastern coast.

Effects caused by Retreating Monsoons

• These tropical cyclones are extremely dangerous.
• Their preferred targets are the densely populated deltas of the Godavari, Krishna, and Kaveri rivers.
• Every year, these cyclones devastate this area.
• The coasts of West Bengal, Bangladesh, and Myanmar have also been hit by cyclonic storms.
• These depressions and cyclones are responsible for the majority of the rainfall on the Coromandel coast.
• In the Arabian Sea, such cyclonic storms are less common.

Significance of Indian Monsoon

• Nearly 60% of India's net arable land is without irrigation and so the monsoon is critical for agriculture.
• The monsoon is responsible for approximately 70% of India's annual rainfall and determines the yield of a variety of grains and pulses, including rice, wheat, and sugarcane.
• Over half of India's population is employed in agriculture, and monsoon rains have a direct impact on their earnings and well-being.
• Agriculture accounts for more than 15% of India's Gross Domestic Product (GDP), so when crops fail due to a lack of rain, the economy suffers.
• Monsoonal Rainfall aids in the storage of water for irrigation, electricity generation, and drinking.

Conclusion

The impact of the monsoon on local weather varies by location. There's a chance of a little more or less rain in some places. In other places, semi-deserts are transformed into lush green grasslands that support a diverse range of plants and crops. The Indian Monsoon transforms vast sections of India from semi-desert to lush greenery. Farmers in places like this must have the right timing for sowing seeds on the fields, as it is critical to use all of the rain that is available to grow crops.

FAQs

MCQs

1. During which months does the Southwest Monsoon occur in India?

A. March to May
B. June to September
C. October to December
D. January to February

2. Which region of India receives the most rainfall from the Southwest Monsoon?

A. Western Ghats
B. Thar Desert
C. Himalayas
D. Deccan Plateau

3. What is the main cause of the Indian Monsoon?

A. Polar winds
B. Differential heating of land and sea
C. Jet streams
D. Tectonic activity

4. Which phase of the monsoon is responsible for rainfall in Tamil Nadu?

A. Southwest Monsoon
B. Northeast Monsoon
C. Pre-Monsoon showers
D. Post-Monsoon depression

5. Which phenomenon is known to negatively impact the Indian Monsoon?

A. La Niña
B. Indian Ocean Dipole
C. El Niño
D. Western disturbances

GS Mains Questions and Model Answers

Q1: Discuss the role of the Southwest Monsoon in shaping the climate and economy of India.

Answer: The Southwest Monsoon is the primary climatic event that shapes the climate and economy of India. It accounts for 75% of the total annual rainfall and significantly influences agriculture, as most of India's crops, such as rice, wheat, and pulses, depend on monsoonal rains. The monsoon is crucial for replenishing water resources, including rivers, lakes, and groundwater, which in turn support drinking water supplies and irrigation. A strong monsoon season results in good agricultural output and economic stability, whereas a weak or delayed monsoon can lead to drought, crop failure, and food shortages, impacting GDP and inflation.

Q2: Analyze the impact of global phenomena such as El Niño and La Niña on the Indian Monsoon.

Answer: El Niño and La Niña are major global climate phenomena that significantly affect the Indian Monsoon. El Niño, characterized by the warming of the Pacific Ocean, weakens the monsoon winds, leading to below-average rainfall and droughts in India. It disrupts the normal monsoon patterns by altering the atmospheric circulation. In contrast, La Niña strengthens the monsoon by causing cooler ocean temperatures, which results in above-average rainfall and sometimes floods. These phenomena underscore the interconnectivity of global climate systems and their impact on regional weather patterns like the Indian Monsoon.

Q3: Explain the significance of the Northeast Monsoon and its contribution to the rainfall in southeastern India.

Answer: The Northeast Monsoon, though lesser known than the Southwest Monsoon, plays a vital role in providing rainfall to southeastern India, particularly to Tamil Nadu and parts of Andhra Pradesh. This monsoon occurs during the post-monsoon period (October to December) and accounts for a significant portion of the annual rainfall in these states. It helps in replenishing water bodies and supporting the cultivation of crops like rabi. The Northeast Monsoon is also critical for irrigation and drinking water supply in the rain-shadow regions of the Western Ghats, where the Southwest Monsoon provides limited rainfall.

Previous Year Questions on Indian Monsoon 

1. UPSC CSE Prelims 2020

Question: Which of the following factors is responsible for the formation of the Indian Monsoon?
A. Polar winds
B. Tectonic activity
C. Differential heating of land and sea
D. Western disturbances

Answer: C

Explanation: The Indian Monsoon is caused by the differential heating of land and sea, which creates pressure differences that drive monsoon winds towards the Indian subcontinent.

2. UPSC CSE Mains 2019 (GS Paper 1)

Question: Discuss the impact of the Indian Monsoon on agriculture in India, with a focus on regional variations.

Explanation: The Indian Monsoon has a profound impact on agriculture, as nearly 60% of India’s cultivated land is rainfed. The Southwest Monsoon is vital for the kharif crops such as rice, pulses, and maize. However, the distribution of rainfall is highly uneven across regions. The Western Ghats and northeastern states receive heavy rainfall, while the Thar Desert and parts of peninsular India receive much less. The Northeast Monsoon contributes significantly to agriculture in Tamil Nadu, where it supports the cultivation of rabi crops. Variations in the timing and intensity of the monsoon can lead to droughts or floods, affecting crop yield and food security across different regions.