Bhubaneswar: There is a good sunset every night, one just can't always see from the ground. Because, the dusts and pollution et al clouds the colourful sunset from your eyes, said lead meteorologist of NOAA, Stephen Corfidi, in his famous book 'The science of colourful sunsets' .
The analysis of Stephen Corfidi proved vindicated on Saturday right here in Odisha, as cyclone Bulbul bid a sour goodbye to Odisha coasts, when the sunset sky lit up quite vividly. Not only vivid sunset, the Sunday morning sun sparkles an azure sky in Bhubaneswar.
While shutterbugs go gaga over the colourful sky, the vindication moment for environmentalists is the parting shot of cyclone Bulbul exposes the spectre of high pollution - dust & vehicular emissions - in the Capital city and elsewhere in the State.
Consider the Skymet data. The PM2.5 concentration at Jayadev Vihar air in the Temple city on Sunday at 11 am was mere 43 micrograms/m3, and the PM2.5 level at Jagmara (near Khandagiri) measured at 42 micrograms/m3. And at the Mancheswar Industrial estate, the PM2.5 level was determined at a measly 2 micrograms/m3.
Since a PM2.5 level of 40-60 micrograms/m3 is within acceptable limits as per Indian air pollution standards, the air quality at Mancheswar has been rated 'good' and termed 'satisfactory' at Jayadev Vihar and Jagmara.
In contrast, just a week ago on November 2 (last Saturday), the PM2.5 level at Jayadev Vihar air was measured at a hazardous level of 331. The value at other locations were recorded as 'poor'. And the evident of high pollution on ground is absence of the colourful sky till this Saturday (Nov 9).
As per the science behind the colourful skies, after major storms, slanting cloud bands are positioned on the back side of the departing weather system, and that act as a sort of projection screen for the low-sun colours in a much better way than a horizontal cloud band could do. It captured more of the orange and red light, and as the cloud is thin it reflected those colours down to the skygazers here on ground.
And since the air is little polluted yesterday, means pollutants like PM2.5 are not trapped in the lower atmosphere, the colourful sunset was the reality.
The big reason behind is the storm Bulbul has washed out a lot of big particles (pollutants) from the air in the cities (Bhubaneswar, Puri etc).
And it's the same science that has made Sunday's morning blue, bright and shiny.
How light reaches from Sun? When a beam of sunlight strikes a molecule in the atmosphere, the phenomenon called "scattering" occurs, which sends some of the sunlight's wavelengths off in different directions.
As the two main molecules in air, oxygen and nitrogen, are very small compared to the wavelengths of the incoming sunlight—about a thousand times smaller, they preferentially scatter the shortest wavelengths, which are the blues and purples. For this reason, the daytime sky is blue.
But at sunset, the light takes a much longer path through the atmosphere to our eye than it did at noon. For which, much of the blue scatters out long before the light reaches us, and that leaves a disproportionate amount of oranges and reds for us to view.