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India’s monsoon season has taken a severe turn.
Following extraordinary rainfall, half of the nation is grappling with extensive flooding, with Punjab experiencing its most significant inundation since 1988.
According to the Indian Meteorology Department (IMD), regions within Punjab, Haryana, and Rajasthan have witnessed rainfall exceeding 1,000% above normal levels within a mere 24-hour period.
Between August 28th and September 3rd, rainfall in northwest India surpassed the average by 180%, while the southern region experienced a 73% increase.
Forecasts indicate continued heavy precipitation across a large portion of the country this week.
The intense rainfall has triggered landslides and widespread flooding, submerging villages and towns and resulting in hundreds of fatalities.
The question arises: What has caused this escalation in rainfall intensity?
The unfolding climate crisis is fundamentally altering the monsoon’s established patterns.
Scientists attribute one primary factor to increased atmospheric moisture stemming from warmer waters in both the Indian Ocean and the Arabian Sea, a consequence of the changing climate.
Historically, monsoon rains were distributed evenly across the four-month period from June to September. However, meteorologists have observed a shift towards concentrated rainfall events, marked by substantial volumes within limited areas over brief durations, often following prolonged dry spells.
Experts note this trend is becoming more pronounced in mountainous regions, where moisture-laden clouds collide with elevated terrain, resulting in rapid and intense rainfall over localized areas – a phenomenon known as a cloudburst.
This phenomenon was a significant contributor to the devastation experienced in the Himalayan states of Uttarakhand, Indian-administered Kashmir, and Himachal Pradesh during the initial week of August.
However, the underlying factors behind the extreme weather events vary geographically.
In August, states such as Punjab and Haryana endured prolonged periods of heavy to extremely heavy rainfall.
Meteorological analysis suggests this was primarily due to interactions between the prevailing monsoon system over the Indian subcontinent and westerly disturbances, low-pressure systems originating in the Mediterranean region and migrating eastward.
These westerly disturbances often transport cold air from the upper atmosphere. When this cold air interacts with the warmer, moisture-rich air associated with the monsoon, it can create conditions conducive to intense weather activity.
“It’s essentially a rare ‘atmospheric tango’ between the monsoon and the westerly disturbance,” explained Akshay Deoras, a research scientist specializing in meteorology at the University of Reading in the UK.
“Imagine the monsoon as a loaded water cannon, with western disturbances serving as the trigger,” he elaborated. “This trigger was pulled forcefully, inundating multiple northern states.”
The IMD has corroborated that the sustained extreme rainfall witnessed across northern India and other regions was largely attributable to the convergence of the monsoon system and westerly disturbances.
“Such interactions are uncommon during the peak monsoon season, as western disturbances typically retreat northward during this period,” Mr. Deoras noted.
The question then becomes: What prompted this eastward detour this year?
Scientists attribute this phenomenon to jet streams – narrow, high-speed air currents in the upper atmosphere that traverse the globe from west to east. They suggest that global warming is causing these currents to become increasingly “wavy,” resulting in deviations from their typical paths and influencing other weather systems.
Research indicates that these wavy jet streams are contributing to extreme weather events worldwide, including the recent occurrences in India, where the subtropical jet stream steered the westerly disturbances atypically far south into northern regions.
“This serves as a stark reminder of how global wind patterns can amplify local monsoon dynamics, transforming the monsoon into chaos, rivers into raging torrents, and the Himalayas into a perilous landscape,” Mr. Deoras stated.
While extreme rainfall during the monsoon season is a primary driver of flooding in India, other factors, particularly related to flash floods and landslides, contribute to the overall risk.
Several areas in northern India and Pakistan, situated downstream from Himalayan rivers, have experienced devastating floods even in the absence of cloudbursts or substantial rainfall.
Scientists propose various contributing factors, including the rupture of overfilled glacial lakes due to rapid glacier melting, the expansion of underground lakes that breach through fissures, and landslides that block rivers, creating temporary artificial lakes which subsequently unleash floods.
While the precise causes remain under investigation, experts emphasize that mountains are exhibiting increased instability due to the accelerated melting of glaciers, snowfields, snowpacks, and permafrost (permanently frozen ground beneath the soil) as a consequence of global warming.
Ice and snow traditionally act as a natural binding agent, maintaining the stability of mountain slopes.
Rainfall patterns also play a significant role.
Experts note that global warming has led to increased rainfall in higher elevations, regions typically characterized by snowfall, further destabilizing mountains as water seeps into the ground and weakens their structural integrity.
“We are witnessing complete snowfields melting within a day or two when subjected to rainfall, resulting in a tremendous surge of water cascading downstream as floods,” stated Jakob Steiner, a geoscientist at the University of Graz.
These factors are compounded by human activities. Encroachment upon river courses and floodplains by settlements, both in mountainous and plains regions, obstructs natural waterways.
Extensive infrastructure development encompassing highways, tunnels, and hydropower plants further compromises mountain stability.
Despite warnings of above-normal monsoon rainfall this year, river embankments and aging drainage systems remain unrepaired in many areas, while plastic waste obstructs waterways intended to mitigate urban flooding.
Experts emphasize that timely action on these issues is crucial to minimizing the impact and losses associated with rainfall and floods.
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