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Name: Johny
Status: N/A
Age: N/A
Location: N/A
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Date: N/A 


Question:
Ten years ago while I was living in Ajijic, Mexico I witnessed lightning flashes in three colors, red, green, and blue. Ajijic is at five thousand feet altitude and I was living in a house higher up in the surrounding mountains. I had just gone to bed, around ten or so as a thunder storm came in and I noticed the strange colors. I got back up and watched this truly wonderful colorful display which lasted thirty to forty minutes. I was at the same altitude as the rain clouds so it was like being in the middle of the storm. The colors were vividly bright and very distinct. The green I could understand as possibly reflection from the green foliage, the blue as possible reflection from the night sky, but the red I have no guess as to its origin. I have never heard or read anyone else describe colored lightning. Is this a known phenomenon or did I witness something truly unusual?


Replies:
Johny,

From what you have written, it was apparently raining and it was dark. It sounds as though there was a great deal of pollution as well, and your position well above the valley would have put you near the top of the daytime atmospheric inversion, where the concentration of pollutants is greatest. At night, there is no solar radiation to obscure weak colors that may have been displayed from the lightning, so that certainly helped you to see the colors.

Normally, during daytime, severe thunderstorms exhibit a green color as water vapor and droplets absorb the red wavelengths of sunlight and aerosols (pollutants, particulates) scatter out some of the blue wavelengths of sunlight. The night that you saw the lightning, the rain and high water vapor content of the air probably absorbed the red wavelengths of light from the lightning, plus aerosols (pollutants, particulates) scattered out some of the blue wavelengths of light to produce the green color of lightning. At other times (during lighter or no rain perhaps), the red wavelengths were prevalent because the aerosols were scattering out all of the yellow and blue wavelengths (similar to a red sunset on a polluted day). At still other times the rain and high water vapor content of the air probably absorbed the red wavelengths of light from the lightning and yellow wavelengths were scattered out by the aerosols, leaving mostly blue light. Furthermore, the presence of high concentrations of ozone (a likelihood if it had been a polluted day) and terpenes (produced by trees on the surrounding mountains) would also tend to make the lightning look blue (similar to the blue tinge that you see in the Blue Ridge mountains when ozone concentrations are high).

You saw different colors from the lightning, depending on what was in the path (rain, water vapor, ozone, aerosols, etc.) between you and the lightning, and being where you were on the mountainside and at an elevation above the valley floor enhanced the likelihood that you would see such a display. Your eyes are also very sensitive to colors from a light placed against a dark background, so that probably helped to enhance the experience.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory


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