Nova Scotia Halos - OPOD

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Nova Scotia Halos - An Enchanting Display of Atmospheric Optics

The captivating image captured by Jeff Dalton in Nova Scotia reveals a mesmerizing display of atmospheric optics during sunset. The sky is adorned with soft halos, each painting the canvas of the sky with its unique geometry. As we delve into the intricacies of this scene, we unravel the various phenomena that contribute to the formation of these enchanting halos.

The cirrus clouds blanketing the sky in this image contain numerous randomly oriented hexagonal ice prisms. These prisms play a crucial role in generating the bright inner 22° halo, which is a prominent feature in the photograph. Additionally, there are plate-oriented crystals present, although they are relatively scarce. These crystals contribute to the formation of weak sundogs and possibly add brightness to the parhelic circle. Furthermore, wobbly or optically imperfect horizontal column crystals give rise to the fuzzy upper tangent arc, adding an ethereal touch to the scene.

While the origin of the outer halo is less apparent, two potential explanations arise. It could be a circular 46° halo formed by randomly tilted crystals or a supralateral arc produced by horizontal columns. To shed light on these possibilities, HaloSim ray tracings are presented. In the left-hand half of the simulation, crystals were adjusted to approximately match the image, resulting in an outer 46° halo. By keeping the randomly tilted crystals shorter, a higher proportion of rays pass between prism side and end faces, enhancing the brightness of the 46° halo. Conversely, by elongating the horizontal columns, most rays pass between side faces, contributing to the formation of the fuzzy upper tangent arc while suppressing the supralateral arc.

In contrast, the right-hand half of the simulation reverses the crystal adjustments. This configuration suppresses the formation of a 46° halo and amplifies the presence of supralateral and infralateral arcs. However, even with these simulations, the outer halo's true identity remains elusive. Crystal imperfections, variations in cirrus thickness across the sky, and lens distortions further complicate the determination of its origin.

Yet, in the grand scheme of things, does it truly matter? The beauty and tranquility of this scene transcend the scientific intricacies of atmospheric optics. The ethereal display of halos against the backdrop of a Nova Scotia sunset is a testament to the wonders of nature. As we gaze upon this photograph, let us revel in the enchantment it brings and appreciate the mysteries that continue to captivate us.

updated_date: September 16, 2023

Exploring the Complexity of Nova Scotia Halos

The captivating photograph captured by Jeff Dalton in Nova Scotia provides a glimpse into the intricate world of atmospheric optics. As we delve deeper into the details of this enchanting scene, we uncover the complexities that contribute to the formation of these captivating halos.

1. Cirrus Clouds: The sky in this image is adorned with cirrus clouds, which serve as the canvas for the mesmerizing display of halos. These clouds consist of numerous randomly oriented hexagonal ice prisms, creating a playground for optical phenomena to unfold.

2. Inner 22° Halo: The prominent feature in this image is the bright inner 22° halo. This halo is generated by the randomly oriented hexagonal ice prisms present in the cirrus clouds. These prisms act as miniature prisms, bending and refracting light to create this beautiful halo.

3. Plate-Oriented Crystals: Alongside the hexagonal ice prisms, there are plate-oriented crystals present in the cirrus clouds. Although they are not as abundant, these crystals contribute to the formation of weak sundogs and potentially add brightness to the parhelic circle.

4. Fuzzy Upper Tangent Arc: The wobbly or optically imperfect horizontal column crystals play a crucial role in creating the fuzzy upper tangent arc. These crystals, with their unique shape and imperfections, refract light in a way that adds a touch of ethereal beauty to the scene.

5. Outer Halo: The origin of the outer halo in this image presents a perplexing question. It could potentially be a circular 46° halo formed by randomly tilted crystals or a supralateral arc produced by horizontal columns. However, determining the true identity of the outer halo remains challenging.

6. HaloSim Ray Tracings: To gain insights into the potential origins of the outer halo, HaloSim ray tracings are employed. By adjusting the crystal configurations, simulations are created to match the image. These simulations reveal the interplay between crystal orientation and halo formation, shedding light on possible explanations.

7. Crystal Adjustments: The simulations show that adjusting the crystal length and orientation can significantly impact the formation of different halos. Shorter randomly tilted crystals enhance the brightness of the 46° halo, while elongated horizontal columns contribute to the fuzzy upper tangent arc.

8. Complex Determination: Despite these simulations, accurately determining the outer halo's true identity remains challenging. Factors such as crystal imperfections, variations in cirrus thickness across the sky, and lens distortions add layers of complexity to the analysis.

9. The Beauty Beyond Science: Ultimately, the true essence of this scene lies not in its scientific intricacies but in its inherent beauty and tranquility. The captivating display of halos against the backdrop of a Nova Scotia sunset transcends our understanding of atmospheric optics, inviting us to appreciate the wonders of nature.

10. A Testament to Nature's Mysteries: As we gaze upon this photograph, we are reminded of the mysteries that continue to captivate us. The ethereal halos dancing in the sky serve as a testament to the awe-inspiring complexity and enchantment that nature effortlessly bestows upon us.

Nova Scotia Halos ~ Sunset approaches in this scene by Jeff Dalton. Soft halos paint the sky with their geometry. Image ©Jeff Dalton, shown with permission

The picture tells us that the cirrus covering the sky had many randomly oriented hexagonal ice prisms of some sort. They generated the bright inner 22° halo. Plate oriented crystals were about too, but not too many. They made the weak sundogs and perhaps added brightness to the parhelic circle. Wobbly or optically imperfect horizontal column crystals made the fuzzy upper tangent arc.

The outer halo's source is less obvious. Is it a circular 46° halo from randomly tilted crystals. Or a supralateral arc from horizontal columns.

Two HaloSim ray tracings are at right. Crystals in the left-hand half were tweaked to roughly match the image with an outer 46° halo. The randomly tilted crystals were kept short. In that way a bright 46° halo would result from the higher proportion of rays passing between prism side and end faces. A supralateral arc from horizontal columns was suppressed by making them very long. In that way most rays passed between side faces and went into the fuzzy upper tangent arc.

On the right-hand half the crystal tweaking was reversed. It suppressed 46° halo formation and enhanced supralateral and infralateral arcs.

Add crystal imperfections, variations in cirrus thickness across the sky and lens distortions. It is just not possible to decide on the outer halo identity.

And does it matter? The scene’s beauty and tranquillity are enough.

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