POLLUTION

Delhi Pollution: Light Rains to Bring Some Improvement In the Capital’s Air Quality This Week

A water sprinkler in action near the India Gate on a hot summer day in Delhi. (Rajesh Mehta/BCCL Delhi) — File photo
(Rajesh Mehta/BCCL Delhi)

Tuesday, November 7: Delhi’s air quality, having undergone a minor improvement since the start of this week, is likely to continue this positive trend in the coming days, with favourable weather aiding this purification process.

After ‘severe’ levels of air pollution over the weekend, Delhi’s overall Air Quality Index (AQI) showed modest improvement on Monday, reaching a ‘very poor’ 399. As of Tuesday noon, it has further improved to a ‘very poor’ 364. For context, AQI classifications include 'good' (0-50), 'satisfactory' (51-100), 'moderate' (101-200), 'poor' (201-300), 'very poor' (301-400), and 'severe' (401-500).

Environmental Minister Gopal Rai named adverse weather conditions as a primary driver of the city's recent pollution spike. “According to scientists and the meteorological department's analysis, the main reason for the rise in pollution within Delhi is the continuous drop in temperatures and very low wind speed,” Rai was quoted as saying.

But now, it looks like the weather might undo some of this damage, triggering some improvement in Delhi’s air quality as the week progresses.

To begin with, the winds across North and Northwest India are likely to pick up starting Wednesday (Nov 8), reaching speeds of up to 12 kmph in Delhi. This shift could aid the dispersion of pollutants trapped within the landlocked capital.

The India Meteorological Department (IMD) has also predicted light rainfall over the northwestern plains, including parts of Delhi-NCR, on Thursday (Nov 9). Some drizzling may even spill over to Friday.

Rainfall plays a pivotal role in reducing air pollution through a process known as wet deposition. As raindrops capture airborne pollutants, these harmful elements are transported to the ground and effectively washed away. This natural cleansing process results in a substantial reduction of pollutant concentration, translating to an improved air quality.

However, the light intensity of these rains will limit their effectiveness, meaning Delhi’s AQI is unlikely to escape the ‘very poor’ category despite the weather turning favourable.

The anticipated wet spell will be triggered by an incoming western disturbance — essentially a low-pressure system that originates over the Mediterranean Sea and moves eastwards while gathering moisture, which then gets dumped over North India.

The impact of this system, likely to be felt in the form of rain and/or snowfall across the Western Himalayan Region and the adjoining plain territories of Delhi-NCR, Punjab and Rajasthan, is expected to persist until Friday (Nov 10). How the capital’s pollution trend moves thereafter remains to be seen.

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