The Unexpected Halo

April 30th, 2016

The final day of the elections! The tangible excitement! Everyone in the back of their minds knew who would win but were nervous nonetheless. I was leisurely sitting on the sofa, flicking through the news channels, hopes dashed that a second news would get preference for a few minutes in at least one of them.

“দিদি দেখ আকাশে সূর্য গ্রহণ হচ্ছে মনে হয়। তাড়াতাড়ি দেখে যা।” (Sister, something’s happening to the Sun! I think it’s an eclipse. Come see fast!)

“সে কি!” (What!) I rushed up the stairs to the terrace. Many fellow flatmates also came up with me and then rushed under the stark blazing Sun. How is it an eclipse when there’s not an iota of shadow visible? Putting on the goggles I had found beside me before coming up, I peered in the direction of the sky. There wasn’t any eclipse, at least grossly. Though what I saw, I’ve never seen before.

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Later on, I got to know it’s a 22 degree halo. It occurs when water vapour freezes 5-10 kilometers above the surface of the Earth, turns into clouds containing hexagonal ice crystals through which the sunrays are refracted twice and then come out in the fashion of a large rainbow colored halo. Thus instead of coming in parallel rays to the Earth as sunlight usually comes, it gets diverted inwards and thus from our point of view it appears circular at the level where it got diverted.

This phenomenon can take place with moon light too.

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Parallel sunlight entering through the hexagonal ice crystal and getting refracted

 

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The mechanism of halo formation

This is rare for us, since 22 degree halos are more commonly formed in cold countries. Even though it had occured here previously in 2013, but I don’t recall about that. Usually they are seen before thunderstorms, as the meterological department reported that day.

Anyways I was stunned to see this, and thought, yes finally the Nor’westers are around the corner! The weather was too hot and sultry to think otherwise! The skies turned dark and promising later that afternoon, but disappointed us by clearing too soon. I was kind of outraged after that, I clearly remember. I mean, there was a beautiful sign in the sky, and now, NOTHING? I’m sure you would’ve felt that way too after enduring a month of 40 degree Celcius and above 80% humidity.

Still, now I feel we were a lucky batch of citizens witnessing a rare event on such an important day in Calcutta.

[For detailed explanation of 22 degree halo, see the Wikipedia page.]

 

 

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24 thoughts on “The Unexpected Halo

  1. Wow!! I have never seen a Halo before. We get to see only spectacular sunrises and sunsets in south India. You were lucky I must say to witness such an event. 😊

    Liked by 1 person

    1. It doesn’t get so cold here unfortunately 😦 that day it did surprisingly, because there was a thunderstorm nearby and it lowered the temperature at that level, then coupled with the Sun’s rays created the halo. Even in winter, Calcutta doesn’t get that cold and the Sun heats the lower atmosphere up like always, indirectly, after the heat waves are emitted from the Earth.

      Like

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