Residents in many parts of Delhi woke up to an azure sky, an unusual sight in one of the most polluted capitals in the world.
A similar natural phenomenon was also noticed by many Delhi residents on August 6, when the sky was unusually blue.
Meteorologists have attributed to Delhi’s unusual blue sky to a raft of factors, albeit what, they said, could be a short-lived affair.
The blue sky would be a temporary natural phenomenon because easterly winds have started blowing and low-pressure area is lying over eastern Madhya Pradesh and Chhattisgarh and that would lead to overcast conditions over the north-western parts of the country as well, according to meteorologists.
Also read:Five reasons that led to Delhi’s monsoon mess
Delhi recorded two “good” air quality days until Thursday (August 20), as compared to the corresponding period last year.
However, the average air quality index (AQI) was lower than last year at 66.1 (satisfactory).
In 2019, the average AQI for the same period was 73.9 (satisfactory).
The blue tint is due to sunshine, a lack of cloud cover and a rain-washed clean atmosphere, meteorologists said. “However, a blue sky can only be seen for a brief period. We must all enjoy the moment, which is pure physics. The radiation has seven colours, and blue gets scattered more because of shorter waves. The blue is more evident than usual because of a lack of cloud cover, sunshine and clean atmosphere,” said K Sathi Devi, head, National Weather Forecasting Centre (NWFC).
Delhi-based Regional Meteorological Centre’s office doesn’t track blue sky days, but officials said that such natural phenomenon was visible in the national capital and north-western parts of the country for the first time in several years.
“We started observing this after the coronavirus disease (Covid-19)-induced lockdown restrictions were imposed. Newspapers also published pictures of the Himalayan peaks being visible from the north-western plains in May following thunderstorms. Delhi was lashed by heavy rains this week that washed away pollution particles. Molecules in the atmosphere scatter white sunlight in all directions. Blue light is scattered more because it travels shorter waves. The obstacles to this scattering are clouds, fog, pollutants and smoke. Now, we have high clouds over Delhi, but they will clear up in a few hours. We will again be able to see a blue sky,” said Kuldeep Shrivastava, head, Regional Weather Forecasting Centre (RWFC), Delhi.
Delhi recorded a “good” air day on Thursday, as the AQI was only 50.
Date 2020 2019
August 20: 50 good 97 satisfactory
August 19: 57 satisfactory 81 satisfactory
August 18: 72 satisfactory 49 good
August 17: 66 satisfactory 49 good
August 16: 52 satisfactory 53 satisfactory
August 15: 67 satisfactory 75 satisfactory
August 14: 58 satisfactory 63 satisfactory
August 13: 50 good 69 satisfactory
August 12: 63 satisfactory 57 satisfactory
August 11: 75 satisfactory 68 satisfactory
August 10: 72 satisfactory 59 satisfactory
August 9: 74 satisfactory 75 satisfactory
August 8: 87 satisfactory 79 satisfactory
August 7: 54 satisfactory 75 satisfactory
August 6: 69 satisfactory 76 satisfactory
August 5: 86 satisfactory 105 moderate
August 4: 62 satisfactory 87 satisfactory
August 3: 67 satisfactory 89 satisfactory
August 2: 61 satisfactory 84 satisfactory
August 1: 81 satisfactory 89 satisfactory
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