Tilting at Clouds in La Manch, Cloud Colours - OPOD

Last updated on September 16, 2023

Tilting at Clouds in La Mancha: Unveiling the Colors of the Sky

Have you ever looked up at the sky and marveled at the colors and patterns displayed by clouds? In the enchanting region of La Mancha, Spain, atmospheric optics expert Stan Gedzelman from Cornell University captured a mesmerizing phenomenon known as cloud colors. These breathtaking images reveal the underside of clouds tinted in a captivating red-brown hue, creating a stunning contrast against the blue sky. Let's delve into the science behind this captivating optical display and explore the factors that contribute to the vibrant cloud colors observed in La Mancha.

The Dance of Light: Unraveling the Colors

The captivating red-brown tint observed on the underside of the clouds in La Mancha is a result of sunlight reflecting upwards from the region's predominantly red soil. This interaction between light and soil creates a unique visual spectacle that has captivated both scientists and sky enthusiasts alike. But how exactly does this phenomenon occur?

When sunlight interacts with the clouds, three main sources of light contribute to the coloring effect:

1. Scattered light from the ground: The light from the red soil below the clouds is scattered upward, adding a reddish tint to the cloud underside.
2. Light from the blue sky: The blue sky also contributes to the overall coloring effect by interacting with the clouds.
3. Transmitted light: Some sunlight passes directly through the cloud, further enhancing the coloration.

Unveiling the Mathematical Model

To better understand and explain this fascinating phenomenon, Stan Gedzelman employed mathematical modeling techniques. His research, published in Applied Optics (54, B167, 2015), revealed several key factors that contribute to the vibrant cloud colors witnessed in La Mancha. These factors include:

• High reflectivity ground: Clouds colored by the ground beneath are most vivid when the ground has high reflectivity, intensifying the interaction between sunlight and the soil.
• Optically thick cloud: The presence of an optically dense cloud is crucial for creating a dark base that enhances the contrast and visibility of the cloud colors.
• Low cloud height: Lower clouds are more likely to exhibit vibrant colors as they are closer to the reflective ground, amplifying the coloration effect.
• Low sky cloud cover: A lower amount of cloud cover in the sky allows more sunlight to reach the ground beneath the cloud, intensifying the coloring effect.
• Relatively low sun position: A lower sun position ensures that the ground beneath the cloud is not shadowed, maximizing the interaction between sunlight and the red soil.

Beyond La Mancha: Colored Clouds in Various Settings

While La Mancha offers a picturesque backdrop for observing cloud colors, this captivating phenomenon can also be witnessed in other locations around the world. Here are some fascinating instances where colored clouds grace the skies:

• Vibrant crops: Colored clouds can be seen above brightly colored crops, such as canola fields. The vibrant hues of these crops contribute to the coloring effect observed in the clouds above.
• Ice Blink: In Arctic regions, scattered light from ice floes and water leads, known as "Ice Blink," can create colored clouds. This natural phenomenon was used by Arctic dwellers as a navigational aid.
• Quasi Images: Water reflects light exceptionally well and can form quasi images on clouds, further enhancing their visual appeal.

Tilting at Clouds: A Spectacle to Behold

The captivating images captured by Stan Gedzelman offer a glimpse into the enchanting world of atmospheric optics. The vibrant cloud colors observed in La Mancha and other settings around the globe showcase the intricate dance between light, clouds, and the surrounding environment. Whether it's the reflection of red soil or the interplay between colorful crops and the sky, these phenomena remind us of the beauty and complexity that exists above our heads.

Next time you find yourself gazing at the sky, take a moment to appreciate the ever-changing canvas of clouds and the myriad of colors they can unveil. The world of atmospheric optics is full of wonders, waiting to be discovered and admired. So, tilt your head back, embrace the beauty above, and immerse yourself in the captivating spectacle of cloud colors.

Tilting at Clouds in La Mancha

The cloud underside is tinted red-brown by sunlight reflected upwards from the region's predominantly red soil.

Imaged around Manzanares, Spain by atmospheric optics expert Stan Gedzelman of Cornell University.

Images ©Stan Gedzelman, shown with permission

The squares show colours spot sampled from the unenhanced image. The background is a neutral grey (RGB, 102,102,102). In contrast the second square from left is (143,138,135) - red enriched.

The cloud underside gets (1) scattered light from the ground, (2) light from the blue sky and (3) some light transmitted right through the cloud. The light from the ground is coloured by the red soil. This cumulus mediocris cloud is optically dense and hardly transmits any sunlight.

Stan Gedzelman mathematically modelled his sighting (Applied Optics 54, B167 (2115)) to find that clouds coloured by the ground beneath are best with high reflectivity ground, an optically thick cloud to give a dark base, a low cloud, low sky cloud cover and a relatively low sun to ensure that the ground beneath the cloud is not shadowed.

Coloured clouds are seen above brightly coloured crops (e.g. canola). 'Ice Blink', scattered light from ice floes and water leads, were used by Arctic dwellers to find their way.

Water reflects so well that it can form a quasi image on clouds.

Reddened cloud at Consuegra of Don Quixote windmills fame.

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Reference Atmospheric Optics

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