The skies over parts of Britain turned a soft shade of pink on Wednesday morning as the low sun shone through layers of widespread fog, producing a rare atmospheric treat.
Meteorologists at the Met Office said the fog formed when temperatures dropped overnight. They issued a yellow warning across a large area of central and northern England where the fog would be slow to clear, which remained in effect until 10am.
Patches of particularly dense fog formed across the East Midlands and Cambridgeshire, where poor visibility was expected to lead to difficult travel conditions. Like clouds, fog is caused by tiny water droplets suspended in the air. It can appear pink because the water droplets scatter short wavelengths of sunlight – the blues and greens – more than the longer red wavelengths, allowing the red to dominate.
A Met Office spokesperson said: “When the sun is low on the horizon, its light travels through more of the atmosphere. Shorter wavelengths are scattered out, leaving the longer red wavelengths to dominate. When this filtered light shines through fog, it gives the fog a pink or rosy hue.”
Dr Claire Ryder, an associate professor at the University of Reading, said the effect was rare because multiple conditions had to be perfect. “You need the fog to occur at the exact sunrise or sunset time, and also for the fog to consist of a perfect thickness, or droplet concentration and droplet size, to get the right effect,” she said. The phenomenon has previously been spotted in the UK in 2019.
