Orange skies in Andalucia

Orange skies and dusty cars? Blame it on Saharan sand

by Kirsty McCabe, FRMetS

 

Desert sand from the Sahara can reach the UK, bringing vivid orange skies and dusty cars. But how does it get here?

It usually begins with strong winds over North Africa kicking up dust and sand. This was the case in March 2022, thanks to strong scirocco winds created by a depression over Morocco – named Storm Celia by the Portuguese Met Office. High pressure centred over the central Mediterranean allowed the dust and sand to be transported northwards into Spain, Portugal, France and the southeast of England.

 

 

In Spain, the phenomenon is known as “calima”, with extremely orange skies spotted over Andulcia and ashy ski slopes in Sierra Nevada.

 

Orange skies over Andalucia
Credit: Dave Cowling, Mojácar (top left) and Neil Foster, Valle del Este (other images)

 

 

In southern France, the snow even took on a pink tinge thanks to the Saharan dust on the slopes in Piau-Engaly ski resort.

 

The dust tends to be high in the atmosphere, creating an orange glow to the sky and some spooky sunsets. Normally, our blue skies and red sunsets are caused by Rayleigh scattering as in the video below. However, due to the larger size of the dust particles, the orange skies are actually due to a similar process called Mie scattering. In addition to this, mineral dust also absorbs the blue wavelengths of light, further enhancing the reddish colour of light that reaches our eyes through the dust plume.

 

 

When it rains, the dust gets washed out of the air, coating cars and other surfaces with reddish deposits. If there is a high enough concentration of red dust particles then the rain can appear red – otherwise known as blood rain.

 

Dust deposits on a yellow car
Credit: Glenis Mould, Hampshire

 

 

Saharan dust in the air can affect air quality and raise levels of air pollution. This won’t affect most people, but those with existing conditions may experience increased symptoms.

Categories: In the Spotlight Weather
Tags: Atmospheric Dynamics Clouds Dust Observations Visibility Weather Wind WorldWeather

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