UPSC Issue at a Glance | Understanding Indian Monsoon: How it forms, what influences it and why it matters
A delayed monsoon can affect markets, strain agriculture and influence policy decisions. But what exactly is the monsoon? How do global climate phenomena shape it? Why is the monsoon called the lifeline of the economy? Here's the science, geography, and economic significance of the rains that power the nation.
For India, the monsoon is not simply a stretch of rainy days but a lifeline of the Indian economy. (Image: AI-generated) UPSC Issue at a Glance is an initiative by UPSC Essentials aimed at streamlining your UPSC Current Affairs preparation for the prelims and mains examinations by focusing on issues making headlines. In this edition, we cover the Indian Monsoon from a broader perspective. Let’s get started.
What is the issue?
The Reserve Bank of India’s (RBI) ‘State of the Economy’ article has cautioned that an adverse south-west monsoon, if it materialises, could weigh on the domestic growth and inflation outlook. As per the updated forecast of the India Meteorological Department (IMD) (released on May 29, 2026), the south-west monsoon (SWM) rainfall is likely to be below normal this year, it said. In this backdrop, understanding the Indian monsoon and its impact on the economy becomes crucial.
Read the article and crack the quiz
What will you learn from this article? |
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Question 1: What is the Monsoon in India?
The monsoon is a seasonal reversal of winds because of differential heating and the resulting pressure differences between land and sea. In summer, land surfaces heat more rapidly than adjacent seas, causing the air above the land to rise and generate a low-pressure area. This low pressure draws in cooler, moisture-laden air from high-pressure regions over the sea. It produces monsoon winds that bring widespread rainfall upon reaching land.
In winter, the process reverses, with winds blowing from the cooler land areas toward the sea, a phenomenon known as the retreating monsoon. This description provides a simplified overview of monsoon circulation.
Types of monsoon in India
There are two notable types of monsoon in India:
(1) Southwest monsoon: It occurs from June to September. It hits Kerala on the southwestern coast and then proceeds across the country. This monsoon is the primary monsoon affecting India, it not only brings respite from the heat but also contributes to the country’s ecosystem and economy, especially the growing of kharif crops. Over 70 per cent of the country receives the majority of its annual rainfall during the June to September season. The country’s Long Period Average is 880 mm.
| What is the Long Period Average (LPA)?
Long period average (LPA) is the average rainfall recorded from June to September, calculated during the 50-year period. It is the benchmark while forecasting the quantitative rainfall for the monsoon season every year. |
(2) Northeast monsoon: It is another significant and persistent aspect of the Indian subcontinent’s climate system. Its name comes from the direction of the monsoon winds, which blow from northeast to southwest. It occurs from October to December and affects peninsular India. It is not as intense as the southwest monsoon but is crucial for the growth of rabi crops.
The northeast monsoon is key for Tamil Nadu, Kerala, Puducherry, Karaikal, coastal Andhra Pradesh, Rayalaseema and Yanam in southern India. Of the total annual rainfall, Tamil Nadu receives nearly 48 per cent (443.3mm) during the October to December months, important for rabi cultivation. The Northeast monsoon is also known as the winter monsoon, retreating monsoon, or reverse monsoon.
Question 2: What are the major factors that affect the Indian monsoon?
As several parts of India continue to reel under extreme heat, the United Nations’ weather agency has warned that a moderate or possibly strong El Niño could develop in the coming months, raising concerns over higher temperatures, erratic rainfall and stress on food and water systems. Against this backdrop, understanding the factors that influence the Indian monsoon becomes crucial.
The monsoon is affected by a complex interplay of atmospheric and oceanic phenomena, with major drivers including the El Niño-Southern Oscillation (ENSO), the Madden-Julian Oscillation (MJO), and the Indian Ocean Dipole (IOD), all of which can significantly affect the timing, intensity, and distribution of rainfall across the country.
El Niño-Southern Oscillation
The El Niño Southern Oscillation is a climate phenomenon marked by changes in sea temperatures along the eastern Pacific Ocean, coupled with fluctuations in the overlying atmosphere. It can alter and interfere with the global atmospheric circulation, which, in turn, influences the weather worldwide. It has three phases: warm (El Niño, Spanish for little boy), cool (La Niña, Spanish for little girl), and neutral. It occurs in irregular cycles of 2 to 7 years.
In the neutral phase, the eastern side of the Pacific Ocean (near the northwestern coast of South America) is cooler than the western side (near the Philippines and Indonesia). This is due to the prevailing wind systems that move from east to west, sweeping the warmer surface waters towards the Indonesian coast. The relatively cooler waters from below come up to replace the displaced water.
During El Niño, the surface waters of this region of the Pacific get unusually warm, disrupting the flow of moist winds in India. The result is a weak or delayed monsoon for India, as well as dry spells in major agricultural states. There is also evidence that the frequency and severity of heatwaves India experiences are linked with the El Niño phenomenon.
The opposite happens when La Niña is underway: cooling of the surface waters of the eastern Pacific. India thus gets stronger, moisture-bearing winds, and typically experiences a boost in its southwest monsoon. In extreme situations, the excessive rain has caused flooding and crop damage as well.
Inter-Tropical Convergence Zone (ITCZ)
The ITCZ is a dynamic region near the Equator where the trade winds of the northern and southern hemispheres come together. The intense sun and warm waters of the ocean heat up the air in this region and increase its moisture content. As the air rises, it cools, and releases the accumulated moisture, thus bringing rainfall. ITCZ plays an important role in the Indian monsoon.
During the monsoon season, this ITCZ is located over the Indian landmass. By September, as temperatures in the northern hemisphere begin to fall, the ITCZ starts moving southwards towards the Equator and further into the southern hemisphere, where the summer season begins to take shape.
Madden-Julian Oscillation (MJO)
MJO is one of the most important and complex ocean-atmospheric phenomena influencing Indian monsoons, with origins in the Indian Ocean. Notably, El Nino is a stationary system, whereas the MJO is a moving system of wind, cloud and pressure that brings rain as it circles around the equator.
A key feature of MJO is that a disturbance of clouds, wind and pressure moves eastward at a speed of 4-8 metres per second. Within 30 to 60 days, MJO wind bands can travel around the world and cause significant weather changes during their movement. In a favourable phase, it can enhance rainfall over India during the monsoon season.
Indian Ocean Dipole (IOD)
IOD is the difference in sea surface temperatures (SSTs) between the eastern and western regions of the Indian Ocean. Like ENSO it also has three phases, positive, negative, and neutral. While a positive IOD leads to more rainfall, a negative phase results in less rainfall. A neutral IOD has minimal impact.
What are the IMD’s colour-coded weather alerts?India Meteorological Department (IMD) issues colour-coded weather alerts from time to time during the monsoon. These keep citizens informed and help in greater preparedness in times of unpredictable weather conditions. Alerts by the IMD are colour-coded from Green to Red. 1. ‘Green’ stands for ‘No warning’: no action needs to be taken by the authorities, and the forecast is of light to moderate rain. According to the weather department, 15.6 mm to 64.4 mm rain is considered “moderate”. 2.‘Yellow’ alert signifies “Watch”, and authorities are advised to “Be updated” on the situation. According to the weather department, 64.5 mm to 115.5 mm rain is considered “heavy”. 3. ‘Orange’ warning stands for “Alert”, and authorities are expected to “Be prepared”. The forecast during an Orange warning is of heavy to very heavy rainfall. According to IMD, 115.6 mm to 204.4 mm rain is considered “very heavy”. 4. ‘Red’ alert stands for “Warning”, and asks authorities to “Take action”. The forecast is for extremely heavy rainfall. The IMD, however, clarifies that “Red colour warning does not mean ‘Red Alert’,” and that it only means “take action”. According to IMD, more than 204.5 mm rain is considered “extremely heavy”. |
Question 3: Why is the Indian monsoon often called the lifeline of the Indian economy?
The Indian monsoon isn’t just an important geographical phenomenon; it holds great economic value as well. The monsoon is the axis around which revolves the entire agricultural cycle of India. It is because about 64 per cent of people in India depend on agriculture for their livelihoods, and agriculture itself is dependent on the southwest monsoon.
Monsoons & the Economic Life in India
Agricultural prosperity in India depends very much on timely and adequately distributed rainfall. If it fails, agriculture is adversely affected, particularly in those regions where means of irrigation are not developed. A good monsoon raises agricultural production, aids GDP growth, and drives up rural earning and consumption. Thus, it has been called the lifeline of the Indian economy.
| What is the Monsoon Mission?
Monsoon Mission is a national programme launched by the Ministry of Earth Sciences (MoES) with a vision to develop state-of-the-art dynamical prediction systems for the monsoon rainfall in different time scales. |
Regional climatic variation in India is reflected in the vast variety of food, clothes and house types. Regional variations in monsoon climate help in growing various types of crops. Winter rainfall by temperate cyclones in north India is highly beneficial for rabi crops.
Post Read Questions
Prelims
(1) The seasonal reversal of winds is the typical characteristic of (UPSC CSE, 2014)
(a) Equatorial climate
(b) Mediterranean climate
(c) Monsoon climate
(d) All of the above climates
(2) With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? (UPSC CSE, 2018)
1. IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
2. An IOD phenomenon can influence an EI Nino’s impact on the monsoon.
Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
(3) With reference to the Monsoons in India, consider the following statements:
1. The southwest monsoon brings more than half of India’s annual rainfall.
2. The ‘above normal’ rainfall is attributed mainly to the El Nino conditions.
3. During the northeast monsoon, the direction of the monsoon winds is from southwest to northeast.
How many of the statements given above are correct?
(a) Only one
(b) Only two
(c) All three
(d) None
(4) With reference to the Northeast monsoon, consider the following statements:
1. About 75 per cent of the country’s annual rainfall is received from the Northeast monsoon.
2. It is confined to the Southern peninsula with Tamil Nadu accounting for maximum rainfall.
3. It is also known as winter monsoon.
How many of the statements given above are correct?
(a) Only one
(b) Only two
(c) All three
(d) None
Mains
How far do you agree that the behavior of the Indian monsoon has been changing due to humanizing landscape? Discuss. (UPSC CSE 2015)
PRELIMS ANSWER KEY
1. (c) 2. (b) 3. (a) 4. (b)
(Sources: RBI Monthly Bulletin: Monsoon shortfall could weigh on growth, inflation outlook, What caused early national coverage by monsoon this year?, Monsoon out, monsoon in, NCERT)
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