Location: Baaigem, East Flanders
Time: October 9, 2006
At least a quarter of an hour before sunset, a very clear rainbow appeared above the horizon, estimated to be about 15°.
There was no precipitation from long before to long after; it certainly wasn’t raining in that direction, there was neither mist nor mist, nor spraying.
At sunset it naturally went out.
Answer
A rainbow needs water droplets to split the white sunlight into its different colours. This has to do with the refraction phenomenon, where colors all have a different refractive index, ie are refracted in a different direction. It really doesn’t have to be raining or to have rained before you see the rainbow, but the air must be humid enough. The small water droplets in the air then have the same effect, if there are enough of them. Since you’re talking about a low rainbow, rising vapor could also have caused the moisture. (How low the rainbow is depends on the position of the sun.)
Answered by
ir Ineke De Coninck
Doorniksesteenweg 145 8500 Kortrijk
http://www.vives.be
.