Hazy sunshine has replaced last week’s fierce heat in parts of the UK, and it’s down to how smoke particles break up rays of light, but along with the lower temperatures, there could be some memorable sunsets and sunrises.
Smoke from wildfires in Spain and Portugal has brought hazy conditions to the UK, breaking up last week’s spell of very hot weather, forecasters have said.
In a post on the X social media platform on Saturday, the Met Office said: “Smoke from wildfires in Spain and Portugal, plus Saharan dust, has drifted over the UK.”
The Met Office said the UK should expect “enhanced sunsets and sunrises in the coming days – deeper reds & oranges thanks to light scattering.”
Sky weather producer Kirsty McCabe said “the very hot weather is easing, thanks to a strengthening easterly wind as well as cloudier skies”.
She said Saturday’s haze is down to “the terrible wildfires that have been raging across Spain and Portugal, and the smoke has made its way to our shores, along with some Saharan dust”.
While the smoke particles shouldn’t affect the UK’s air quality, she said they will “enhance the orange and red colours of our sunsets and sunrises”.
Wildfire smoke affects the colour of the sky through processes known as Rayleigh scattering and Mie scattering, she explained.
On reaching the Earth’s atmosphere, the sun’s light bumps into tiny molecules of nitrogen and oxygen, which scatter or deflect the light.
Kirsty McCabe said Mie scattering occurs “when the [smoke] particles are much larger and closer to the wavelengths of light.
“That means the smoke particles in the air scatter all colours of light more equally, leading to a hazy or milky appearance of the sun and sky.”
Rayleigh scattering sees the shorter wavelengths of light, blues and violets, scattered most strongly, while red light, having the longest wavelength, is scattered the least, she explained.
“At dusk and dawn, the sun’s rays travel through a greater distance of atmosphere to reach our eyes, so the blue light has been scattered even more.
“With most of the shorter blue and violet wavelengths filtered out, along with some green and yellow, that leaves us with the warmer hues of the reds and oranges.”
