The changing face of monsoon

As per the India Meteorological Department (IMD), instances of heavy rainfall have increased by almost 85% in the country since 2012 (Image: Marina, 2009,Wikimedia Commons)
As per the India Meteorological Department (IMD), instances of heavy rainfall have increased by almost 85% in the country since 2012 (Image: Marina, 2009,Wikimedia Commons)
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The farmers of Mukhtsar, Punjab, are keeping a close eye on the sky like millions of other small farmers whose livelihoods depend on the yearly monsoon. Only farmers who had grown mustard in rabi are sowing cotton now because the harvesting of the rabi wheat was delayed due to the early rains. Untimely rains and hailstorms had ravaged the standing wheat crop, causing high-velocity winds to lodge or cause the grain to bend over, which delayed harvesting. Most of the farmers have abandoned the cash crop of cotton in favour of paddy in this kharif since it seems safer to them. Many farmers claim that over the past few years, the weather has largely remained unpredictable, and cotton turns out to be a risky crop.

According to a recent report, unexpected rainfall has harmed agriculture (paddy and maize) on around 5,000 hectares of land throughout Nandyal in the Andhra Pradesh districts of Rayalaseema, East Godavari, Konaseema, and Krishna. About 2,000 hectares of horticulture crops like bananas and mango across several districts were affected by rains. Once the rain stops and the daytime temperature begins to rise in the hot summer of May, the farmers are optimistic that they can save their lodged crops. However, not all farmers are as fortunate as them.

Every now and again, poor, and premature rains have spelt disaster for India's agriculture. This year's (2022-23) rains and hailstorms are to blame, but previous year's (2021-22) wheat crop in the states of Punjab, Haryana, western Uttar Pradesh, Rajasthan, and Madhya Pradesh suffered from heat stress. Although the damage has not yet been formally determined, the farming community and trade, as reported in the Financial Express, estimate a potential output loss of 10% this year.

Around 70% of the nation's annual rainfall is attributed to the monsoon, which also irrigates 60% of its net sown area. Agriculture is a direct or indirect source of income for nearly half the population. Crop production and inflation are invariably poor after a bad monsoon.

India is currently experiencing a prolonged wet season in many areas, and it is feared that it will delay the monsoon. Data from the India Meteorological Department (IMD) show that the maximum temperature has been below the 40-degree Celsius threshold for the past three days throughout India. This could lead to a delay in the onset of monsoon, it is feared. In India, the monsoon season officially starts on June 1. The south-west or summer monsoon is essential for the nation's agricultural production in addition to providing relief from the heat.

Although this wet season is unusual, according to a recent Press Trust of India release, the cooling of the landmass caused by it will not delay the arrival of monsoon. The temperature and pressure differences between the Indian landmass and the Indian Ocean are what cause the Indian monsoon. As the landmass warms up in the summer, a low-pressure zone is formed that pulls moist air from the ocean, causing rainfall. There are worries that there won't be as much power to pull in the moist air from the ocean and as a result, the arrival of monsoon rains may be delayed. But scientists have refuted this and state that the spell will possibly be over in another week. The usual conditions of the pre-monsoon season -- heat and thunderstorms -- will commence after this.

The complexity of the Indian monsoon

The Indian monsoon is a complex and dynamic weather phenomenon, and its trends can vary from year to year. However, over the long term, there are certain patterns that have been observed. It involves a complex interplay of many factors. The monsoon is driven by a combination of factors, including the differential heating of land and sea, the distribution of atmospheric pressure, the flow of moisture from the oceans, and the interaction of the monsoon winds with local topography.

Impact of large-scale weather patterns

Between 2019 and 2022, India experienced four years of strong monsoons and overall rainfall. La Nina, an oceanic and atmospheric phenomenon which is characterized by lower-than-normal air pressure over the western Pacific has been heavily cited for the abundant rainfall during 2019–2022.

The monsoon is also affected by larger-scale weather patterns, such as the El Niño Southern Oscillation (ENSO), and the Indian Ocean Dipole (IOD). ENSO is a climate pattern that occurs in the Pacific Ocean and affects weather patterns around the world. During an El Niño event, the sea surface temperatures in the equatorial Pacific Ocean become warmer than normal, which can lead to changes in atmospheric circulation patterns. El Niño events are typically associated with reduced rainfall over India, while La Niña events, which are characterized by cooler sea surface temperatures in the Pacific, can enhance the monsoon.

The IOD is another climate pattern that affects the Indian monsoon. It is a seesaw-like pattern of sea surface temperature anomalies in the Indian Ocean, with warmer water in the western Indian Ocean and cooler water in the eastern Indian Ocean during a positive IOD event. Positive IOD events have been associated with below-average rainfall in India.

In addition to ENSO and IOD, there are other climate patterns that can influence the Indian monsoon, such as the Madden-Julian Oscillation (MJO) and the North Atlantic Oscillation (NAO). These larger-scale weather patterns interact with the complex monsoon system, making it challenging to predict and understand.

In addition to these physical factors, the monsoon is also influenced by social and economic factors, such as changes in land use and agricultural practices, which can affect the availability of water and impact the overall health of the monsoon system. All these factors contribute to the complexity of the Indian monsoon and make it a challenging system to predict and understand.

Trends observed in Indian monsoon

One trend that has been observed is that the monsoon season has become more erratic in recent years, with fluctuations in the timing and intensity of rainfall. While the overall amount of rainfall during the monsoon season has not decreased significantly, there has been more variability in the timing and distribution of rainfall. For example, some regions have experienced more intense rainfall events, while others have experienced more frequent and prolonged droughts. The monsoon season has also been starting and ending later than usual, and there have been more instances of sudden and heavy rainfall, which can cause flooding and landslides.

This increase in variability and unpredictability of the monsoon has been attributed to climate change. As global temperatures rise, they can alter atmospheric circulation patterns, which in turn affect the behaviour of the monsoon. In addition, changes in land use and other human activities can also impact the monsoon system, making it a complex and dynamic phenomenon.

It's worth noting that the Indian monsoon is a highly complex system, and it is subject to natural variability as well as the impacts of human activity. Therefore, it can be difficult to isolate the specific effects of climate change on the monsoon. Nonetheless, there is growing evidence that the monsoon is becoming more erratic, and this trend is expected to continue in the future.

Source: Changing Rainfall Patterns in India: A Spatiotemporal Analysis of Trends & Impacts, Research Square

Another trend is that the monsoon season has been getting longer. In the past, the monsoon season typically lasted from June to September, but now it often begins earlier and extends into October. In terms of overall rainfall, there has been some variability in recent years. For example, 2019 was a particularly wet year, while 2020 was relatively dry. However, over the long term, there has been a slight increase in overall rainfall during the monsoon season. While these trends provide some insights into what we might expect in the future, it's difficult to make specific predictions about the monsoon with certainty.

Most global models predict climate warming will make Indian summer monsoons intense

Climate change is expected to have significant impacts on the Indian monsoon. More intense rainfall events may increase the risk of flooding and landslides in some areas, while other regions may experience more frequent and prolonged droughts. “Variability of the Indian summer monsoon has increased significantly since the 1950s. For several regions across India, this means an increase in long dry periods with low or no rainfall, intermittent with short, intense spells of rainfall. These changes are particularly significant for the western, central and eastern states of India where more than 55% of the cultivated area is largely rainfed and where the adaptive capacity is the lowest.” (Roxy M K and Chaithra S, MoEF, 2018)

Climate models predict that there will be changes in the distribution and timing of rainfall during the monsoon season. “Increased precipitation including monsoonal rains is likely to come in the form of fewer rainy days but more days of extreme rainfall events, with increasing amounts of rain in each event, leading to significant flooding. Drizzle-type precipitation that replenishes soil moisture is likely to decrease. Most global models suggest that the Indian summer monsoons will intensify. The timing may also shift, causing a drying during the late summer growing season.” (NIC, 2009)

Rising temperatures can alter the dynamics of the monsoon system, leading to changes in wind patterns and atmospheric circulation. This, in turn, can impact the timing and amount of rainfall.

Monsoon is critical for agriculture in India, and changes in rainfall patterns and temperatures can have significant impacts on crop yields. For example, prolonged droughts or flooding can lead to crop failures and food shortages. Monsoon is a major source of water for many regions in India, and changes in rainfall patterns can affect water availability for drinking, irrigation, and other uses. Changes in rainfall patterns and temperatures can also affect human health, as they can lead to the spread of waterborne diseases, heat stress, and other health risks.

Overall, the impacts of climate change on the Indian monsoon are expected to be significant and wide-ranging, and they will require adaptation and mitigation measures to minimize their effects on people and ecosystems.

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Post By: Amita Bhaduri