Fog

I remember, when I was a boy growing up in London, how there would be foggy days when we could hardly see to the other side of the road. Those days are largely gone but every so often there is a foggy day which now makes the news. The picture below was taken recently and shows something about which we were never aware when I was young: that the fog had a vertical limit. It seemed  to us at ground level that the fog went on indefinitely - quite literally into the clouds. That seems not to be the case.
As I've noticed whenever I've taken off in a plane from a rainy airport, above the clouds the sun is always shining.

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