NASA Captures Delhi-NCR's Worrying Air Quality from Space; Photograph Shows Smoky Skies Blanketing North India!

Earlier this week, NASA's earth observatory released satellite images displaying a plume of smoke curling about northeastern Pakistan and extending to the Indian states and UTs of Delhi, Haryana, Uttar Pradesh and Punjab.

While aesthetic to look at, the picture conveys the severity of the sharply deteriorating conditions in the Indo-Gangetic Plains, and Delhi-NCR in particular.

On November 1, the air quality index in the capital rose as high as 424, as per the Central Pollution Control Board. This put it in the "severe" category, forcing officials to halt construction in Delhi and urging the residents of the capital to work from home.

There are, of course, multiple reasons for this annual degradation in the national capital region's air quality.

Influxes of dust sometimes arrive from the Thar Desert to the west, like on October 31. Other human-caused sources of air pollution come from cities, including motor vehicle fumes, industrial and construction activity, fireworks, and fires for heating and cooking, contributing to the pollution levels.

Moreover, geography and weather also worsen the region's air quality problems. Temperature inversions are common in the months of November and December when air rolls off the Tibetan Plateau and mixes with smoky air from the Indo-Gangetic plain. This phenomenon serves as a lid, with warm air trapping pollutants near the surface and helping hem pollutants in between the northern Himalayan Mountains and southern Vindhya Mountains.

Once the crops have been harvested after the Kharif season, a 'stubble' of the crops still remains on the fields. And since this takes over a month to decompose on its own, farmers who need to sow the next crop as soon as possible are driven to burn the stubble to speed up the process. However, the winds end up transporting this stubble smoke to Delhi-NCR, resulting in the capital's AQI plummeting further.

Measurements of particulate matter, including the small particles known as PM2.5, can be used as a proxy for air quality. According to one analysis of Delhi's air pollution, stubble burning contributed 14% of PM2.5 in Delhi on November 1. Before the start of widespread crop fires, the percentage ranged from 1 to 3%, NASA reported.

The crop-burning season has just begun and typically lasts for two to three weeks. And it remains to be seen how Delhi-NCR and the rest of North India will fare at the end of this season.

As of Saturday evening, Delhi's overall AQI stands at 363 as of 5:30 PM, putting it in the 'very poor' category. Its PM2.5 levels stood at 202 and PM10 at 321, according to the System of Air Quality and Weather Forecasting And Research (SAFAR).

The AQI is likely to improve due to unfavourable upper-level wind flows from stubble-burning areas preventing the inflow of pollutants to Delhi. Stubble emissions with a fire count of 1761 contribute 21% to PM2.5 in Delhi.

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