Western Disturbance: Significance, Causes, and Impact
A common question that may arise while learning about India’s climatic conditions, is how come the northern regions of India experience a pattern of rainfall that is not equivalent to that in the central or the southern part of the country.? This difference in rainfall pattern in the subcontinent is mainly because of the extratropical storms in the area called the western disturbance. These winds bring abrupt rainfall to the country during the non-monsoon seasons.
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What are Western Disturbances?
- A Western disturbance is a storm that originates in the Caspian or Mediterranean Sea and brings non-monsoonal rainfall to northwest India, according to the India Meteorological Department (IMD).
- They are labelled as an extra-tropical storm originating in the Mediterranean, an area of low pressure that brings abrupt showers, snow and fog in northwest India.
- The disturbance goes from the “western” to the eastern direction.
- This movement eastwards on high-altitude westerly fly streams – massive ribbons of quick winds traversing the earth from west to east.
Western Disturbances Mechanism
Western disturbances UPSC questions dive profound into the formation and mechanism of this storm since its impacts are colossal for the agriculture of India. Since it is a cyclone, it originates in the ocean, so it picks up so much moisture on its way. How tropical storms function is that they pick up moisture in the upper atmosphere and provide rainfall to the lower atmosphere, but in this case, the air causing the storm originates in Ukraine.
The UPSC test includes questions regarding how this storm heads out from Ukraine to Northern India and what forces it to do so. The high-pressure region in Ukraine creates a virus air intrusion from the polar regions with high moisture.
This makes an extratropical depression toward the east movement, and this depression moves to the Indian subcontinent at a relatively quick speed. However, once it arrives at the Himalayan mountain range, it stops developing.
Western Disturbance: Significance and Impact
The rainfall distribution and sum vary with every western disturbance.
Western disturbances are normally associated with cloudy skies, higher night temperatures and uncommon rain. Excessive precipitation because of western disturbances can cause crop damage, landslides, floods and avalanches. Over the Indo-Gangetic plains, they occasionally bring cold wave conditions and thick fog.
The strongest western disturbances generally happen in the western and northern parts of Pakistan, where flooding is reported several times during the winter season.
Effects of Western Disturbances in India – UPSC
The UPSC prelims often pose inquiries regarding the immediate and long-term impacts of this storm on India. As stated earlier, they are vital for the development of Rabi crops that fill in the winter, like privately created wheat. One of the reasons this storm is associated with agriculture is that rainfall dictates the fertility and compatibility of soil for crop development.
However, the western disturbances are not always a blessing since they also cause a lot of soil erosion. Since the rainfalls are scattered and the density is quite high, it often brings about the topmost layer of the earth getting washed away in the regions of Northern India.
Moreover, in the case of very heavy rainfall, significant crop damage is also noticed, especially with the formation of thick fog and mist. In conclusion, the heavy downpour also brings about severe landslides and even avalanches in the region.
Equilibrium exists in nature because of which the air in a region tries to normalize its pressure.
In the expression “extra-tropical storm”, storm means low pressure. “Extra-tropical” signifies outside the tropics.
The moisture which WDs convey with them comes from the Mediterranean Sea and additionally from the Atlantic Ocean.
Sometimes WDs can cause outrageous weather events like floods, streak floods, landslides, dust storms, hail storms and cold waves killing individuals, destroying infrastructure and impacting livelihoods.
What is the Variation in Western Disturbances?
In 2021, Delhi witnessed the rainiest October in 65 years, with the Safdarjung weather observatory recording 122.5 mm of rainfall against an ordinary of 28 mm, by western disturbances.
An abundance of rainfall was also kept in January and February this year. In contrast, there was no rainfall in November 2021 and Walk 2022, and the mid-year saw a curiously ambitious beginning with heat waves setting in at the finish of Walk 2022.
Multiple western disturbances that brought cloud cover also kept the maximum temperature low in February 2022, when the lowest maximum temperature in 19 years was recorded.
Active western disturbances escaped northwest India in Walk 2022, and the nonappearance of cloud cover and rain permitted temperatures to remain high.
What is the Reasonable justification for the Variation?
- The recurrence of western disturbances has increased, but not the precipitation associated with them, partly because of a warming atmosphere (Global Warming).
- Western disturbances are low-pressure areas. If it is a weak western disturbance, it will not have moisture to precipitate.
- For precipitation, you need moisture, and with a warming atmosphere, there is less measure of moisture available to precipitate.
- As a rule, they move in subtropical westerly flight, now they are becoming lighter and moving higher, over 200 hectopascals.
- Variations will have to be monitored over the following couple of years to determine what climate change impact might be.
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