How a dust storm from 3,000 km away smothered Delhi this month 

How a dust storm from 3,000 km away smothered Delhi this month 

Context:

The System of Air Quality and Weather Forecasting and Research (SAFAR) under the Ministry of Earth Science published a ‘Scientific Assessment of Delhi Winter Air Quality Crisis’, which listed two “Extreme” events behind the smog that had smothered Delhi and its neighbourhood.

“Extreme 2”

• Extreme 2 was the much discussed burning in Punjab, Haryana, and Uttar Pradesh

“Extreme 1”

• was a “large multi-day dust storm that emerged at Iraq, Kuwait, and Saudi Arabia
• The report blamed this storm much more than the burning of stubble for Delhi’s air quality crisis during that period –“the pollution contribution of Gulf dust storm on peak day was around 40% and from stubble burning was 25%.

Introduction:

• The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NOAA/NASA Suomi  NPP satellite captured images of a massive dust and sand storm over Saudi Arabia  and Iraq .
• Moderate Resolution Imaging Spectroradiometers(MODIS) aboard NASA’s Terra and Aqua satellites released images of skies over Saudi Arabia and Iraq ,red with a thick blanket of dust.

Reasons:

• Scarce rain and advancing desertification are the key reasons.
• Climate change is the main reason which led to drastic changes in annual rainfall and temperature besides other reasons such as drought, mismanagement of water, and abandonment of agriculture lands.

Highlights of the report:

• According to the SAFAR assessment, the late October-early November dust storm “was carried by relatively cool winds”.
• The report pointed out that “As air temperatures dropped, winds and dust were likely to slowly diminish, but that time, it got into the upper part of atmosphere and direction became towards India and dust affected the larger region of NCR including Delhi.
• The strong NW shaman winds entrained an enormous amount of mineral particles into the atmosphere.

Pollution in Delhi:

• A high-pressure centre developed above the Gulf of Oman and the strong anticyclonic flow at 5,500 metres above sea level transported atmospheric dust into the direction of Delhi.
• Meteorologists in India have said that a high-pressure zone over Delhi and its neighbourhood and the absence of strong winds kept pollutants trapped close to the surface.
• During the second week of November, anti-cyclonic weather conditions were observed in North India, which helped in building up of pollutants in the lower troposphere.
• The calm surface wind conditions which do not allow to disperse pollution was due to anti-cyclonic circulation connected with late withdrawal of monsoon, persisting at about 700 hPa lower troposphere over northwest India with its centre near Delhi.
• Stubble burning, which , the SAFAR report said, was very high and upper air winds become north-westerly with high speed and started pumping pollution in Delhi.