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Name: Brian
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 2000-2001


Question:
Last week I was walking along a beach, around midnight looking out to sea and observed a distant thunderstorm - It was too far away to hear the thunder. The lightning flashes were distinctly yellow rather than the normal blue-white color. I asked others from the local town and villages about it and they also confirmed that it was a strong yellow color. Can you explain why this was, and why lightning is normally blue-white and not some other color?


Replies:
Brian,

You basically explained why the color was yellow by saying that the thunderstorm was far away. Just as the moon appears yellow when near the horizon, the shorter wavelengths of the light from the lightning were scattered out by the atmosphere, leaving the longer wavelengths (yellow, red) to be seen. The sun, when right on the horizon, sometimes appears red because there is sufficient water vapor, aerosols, and other pollutants to scatter out even yellow light. The lightning, being both far away and in proximity to a lot of water vapor and water droplets (over the ocean and associated with a storm) was seen as yellow.

As far as the color of lightning, even when seen close, natural lightning usually appears somewhat yellowish. I have only seen the blue-white color that you describe when I witnessed a man-made spark, and particularly when it was in pure air or another gas, having no contaminants. The contaminants in natural air scatter the short wavelengths, leaving a pale yellow tinge to the light.

Having performed lightning research both for natural and triggered lightning and large sparks outdoors, I have to say that I have never seen pure white lightning outdoors.

I hope that these explanations help.

David Cook


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