Unusual Rainbow

oes anybody know anything about this?

On Monday 12/20/99, I was driving west on I-20 in Arlington, TX when I noticed a vertical rainbow to the West-Southwest about 20o to the left of the setting sun which was about 7 to 8o above the horizon.

The rainbow was fairly distinct and extended upward about 10o (by outstretched ed open hand = ~20 method) or so till it was no longer discernible. It was about 1o wide more or less (using moon =1) and I think the red end was nearest the sun (not positive). I looked to the northwest to see if there was a nother vertical "piece" where it might be coming down ... nothing. Then to the southeast to see if it might terminate in the other direction ... nothing.

My wife and sister-in-law were also able to see it (though they were not at all impressed - yak yak yak shop shop shop). What impressed me was the weather conditions which I thought were not at all conducive to the formation of a rainbow (namely, after a rain). You need water droplets to refract the light into the rainbow shape.

There was no rain that day.

In fact, I had remarked earlier to myself about how dry the air was compared to the high humididty of a few days earlier. And ... it was cold (maybe 45oF)

In the distance there were a few clouds (not rain clouds), one of which was either in front of the rainbow or behind ... I couldn't tell which. So the rainbow might have been 10 miles distant (but not much more).

The question:

What is going on here? Am I missing something? Does anyone know what it might be? How do you get a rainbow without water droplets? I would have expected perhaps that there might have been some ice crystals up there ... but as far as I know no rainbow can form from them ... and ... I don't recall being able to see a rainbow and the sun simultaneously (the sun is generally at your back ... isn't it? After a rain?).

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