INDIA'S EXTREME RAINFALL CORRIDOR
1. Context
The Indian monsoon has well-known features, such as the onset of the monsoon, the withdrawal, the active and break periods, and the low-pressure systems (or monsoon depressions). Every aspect of the monsoon has been affected by global warming. The total seasonal rainfall has also trended downwards for more than seven decades, due to the differential heating of the land versus the ocean due to global warming. However, this trend has been distributed unevenly through the monsoon season — as manifest in the longer duration but lower intensity of dry spells and the greater intensity of wet spells. While the India Meteorological Department (IMD) has made progress in forecasting extremes, multiple factors can combine to still produce devastating heavy rain events that remain hard to anticipate
2. Region where high rainfall Occurs
- India's monsoon predictions heavily hinge on their association with El Niño and La Niña phenomena, although this link holds true only about 60% of the time.
- While other global connections exist, translating them into more accurate forecasts necessitates meticulous modeling experiments.
- Researchers persist in seeking further comprehension, especially concerning impactful extreme rainfall occurrences. A recent study, involving the author, has revealed an intriguing consistency amidst various alterations in monsoon dynamics.
- These widespread extreme rainfall incidents, referred to as large-scale events, represent simultaneous or nearly simultaneous periods of intense rain distributed along a 'highway' spanning from regions in West Bengal and Odisha to parts of Gujarat and Rajasthan.
- The most striking revelation is the persistence of this corridor, unchanged from 1901 to 2019.
- Amidst the apparent disorder in various monsoon elements, the confinement of extreme events within a relatively narrow corridor presents encouraging prospects for refining our understanding. This, in turn, could lead to enhanced predictions of these synchronized extreme rainfall events
3. Monsoon Stability
- Conventional statistical approaches often fail to capture the intricate connections between multiple centers of rainfall distribution.
- Utilizing rainfall data from IMD at a 25-km resolution in latitude and longitude, a dataset with considerable depth, sophisticated network analysis becomes feasible, enabling the identification of nodes exhibiting the highest synchronicity in rainfall with neighboring nodes, both nearby and distant.
- In the context of this study, this analysis revealed that the most active nodes have consistently followed a specific 'highway' for more than a hundred years. Moreover, the distances linking these nodes, representing the scales of synchronicity, have remained relatively stable, averaging around 200 km.
- To illustrate this phenomenon, one can draw an analogy using popcorn and a kettle. Central India acts as the kettle, warming up from pre-monsoon to monsoon.
- The rainfall systems during the monsoon resemble kernels of corn popping sporadically within the kettle. However, these kernels exhibit synchronous 'popping,' suggesting that large clusters of popcorn are leaping up simultaneously.
- Analysis of wind patterns and other atmospheric circulation characteristics indicates that the monsoon region has sustained a notable stability conducive to the formation of these extreme rainfall events. This stability has persisted despite various influences originating from tropical oceans and spanning from pole to pole
- Monsoon stability in India refers to the consistency or predictability of the seasonal monsoon patterns that bring significant rainfall to the region.
- It encompasses the reliability of monsoon onset, duration, and the distribution of rainfall across different regions within the country.
- Stability is gauged by assessing how consistently the monsoon behaves in terms of its timing, intensity, and spatial coverage from year to year.
- When the monsoon exhibits stability, it allows for better agricultural planning, water resource management, and overall economic activities dependent on rainfall.
- Conversely, instability or erratic behavior of the monsoon can lead to droughts, floods, and agricultural uncertainties, impacting the livelihoods of millions of people in India. Understanding and predicting the stability of the monsoon is crucial for the country's agricultural productivity and overall socio-economic stability.
4. Findings and Forecast
- Certain researchers have argued that due to global warming, stationary aspects no longer persist within climate systems.
- However, the Indian monsoon continues to present unexpected phenomena by effectively coordinating intense rainfall occurrences and adhering to a consistent 'highway' pattern over an extended period.
- Notably, this pathway also serves as the route for the monsoon depressions, which have exhibited an increase in occurrences at shorter timescales of 3 to 10 days while decreasing at longer frequencies ranging from 10 to 60 days.
- These alterations are evident during active and break periods, as previously mentioned. The primary factor potentially responsible for confining synchronized extreme rainfall seems to be the mountain range stretching along the west coast and through Central India.
- Although this proposition necessitates testing within models, its implications for enhancing predictions of such occurrences are undeniable.
- Moreover, it indicates that augmenting model resolution and computational expenses might not be essential. Rather, emphasis can be directed toward comprehending the dynamics of synchronization.
- The prospect of mitigating risks posed by large-scale extreme rainfall events at a smaller scale impacting agriculture, water resources, energy, transportation, health, among others is enticing. Fortunately, India possesses substantial modeling capabilities and computational resources, positioning it favorably to fully exploit this potential
5. How has the Indian monsoon been affected by global warming?
Global warming has significantly impacted the Indian monsoon, altering its patterns, intensity, and behavior in various ways:
- There have been shifts in the distribution and intensity of rainfall during the monsoon season. Some regions experience heavier downpours leading to increased flooding, while other areas face prolonged dry spells and droughts. This variability affects agriculture and water resources
- The timing of the monsoon's onset and withdrawal has been observed to fluctuate. Sometimes, the onset might be delayed or arrive earlier than usual, affecting planting and harvesting seasons
- Global warming has led to an increase in extreme weather events within the monsoon season, such as intense rainfall over short periods, which can result in flooding and landslides
- Erratic rainfall patterns and extreme events impact crop yields, affecting agricultural productivity and food security in the region
- Rising temperatures during the monsoon season can lead to heat stress and various health issues, affecting vulnerable populations
- The warming of oceans, including the Indian Ocean, alters the moisture content and atmospheric circulation patterns, influencing the monsoon's behavior
6. Way forward
Overall, while the Indian monsoon has always been variable, global warming exacerbates this variability, leading to more erratic and unpredictable behavior with significant implications for various sectors and communities dependent on monsoon rainfall
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For Prelims: El Nino, La Lina, GDP, Rainfall, sea surface temperatures, El Nino Southern Oscillation, Monsoon, US National Oceanic and Atmospheric Administration, Oceanic Nino Index,
For Mains:
1. What is El Nino? Explain El Nino Threat to India's Monsoon and discuss its impact on Indian Agriculture. (250 Words)
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Previous Year Questions
1. A new type of El Nino called El Nino Modoki appeared in the news. In this context, consider the following statements: (UPSC 2010)
1. Normal El Nino forms in the Central Pacific ocean whereas El Nino Modoki forms in the Eastern Pacific ocean.
2. Normal El Nino results in diminished hurricanes in the Atlantic ocean but El Nino Modoki results in a greater number of hurricanes with greater frequency.
Which of the statements given above is/are correct?
A. 1 only B. 2 only C. Both 1 and 2 D. Neither 1 nor 2
Answer: B
2. La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino? (UPSC 2011)
1. La Nina is characterized by unusually cold ocean temperature in the equatorial Indian Ocean whereas El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
2. El Nino has an adverse effect on the south-west monsoon of India, but La Nina has no effect on the monsoon climate.
Which of the statements given above is/are correct?
A. 1 only B. 2 only C. Both 1 and 2 D. Neither 1 nor 2
Answer: D
3. Consider the following statements: (MPSC 2017)
a. La Nina is a little girl.
b. During the time of La Nina cold water in the ocean rises to the surface.
c. La Nina strengthens the Indian monsoon.
d. During the time of El Nino, trade winds weaken, and warm water moves east in the ocean. Which of the above statements is/are correct?
A. Only a and b B. a, b and c C. Only b and c D. All of the above
Answer: D
4. Gross Domestic Product (GDP) of a country is (SSC CGL 2022)
A. Total value of tradable goods produced in a year.
B. Total value of monetary and non-monetary goods and services within a year.
C. Total value of economic transactions done within a country within a year.
D. None of the above
Answer: D
5. With reference to India economy, consider the following statements: (UPSC 2015)
1. The rate of growth of Real Gross Domestic Product has steadily increased in the last decade. 2. The Gross Domestic Product at market prices (in rupees) has steadily increased in the last decade.
Which of the statements given above is/are correct?
A. 1 only B. 2 only C. Both 1 and 2 D. Neither 1 nor 2
Answer: B
6. With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? (UPSC 2020)
1. OMT is measured up to a depth of 26°C isotherm which is 129 meters in the south-western Indian Ocean during January-March.
2. OMT collected during January-March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.
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
Answer: B
7. 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 2017)
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
Answer: B
8. "EL Nino" refers to a temperature anomaly in the ________ ocean. (NTPC 2017)
A. Indian B. Pacific C. Southern D. Atlantic
Answer: B
9. The acidification of oceans is increasing. Why is this phenomenon a cause of concern? (UPSC 2012)
1. The growth and survival of calcareous phytoplankton will be adversely affected.
2. The growth and survival of coral reefs will be adversely affected.
3. The survival of some animals that have phytoplanktonic larvae will be adversely affected.
4. The cloud seeding and formation of clouds will be adversely affected.
Which of the statements given above is/are correct?
A. 1, 2 and 3 only B. 2 only C. 1 and 3 only D. 1, 2, 3 and 4
Answer: A
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Source: The Hindu
