There seem to be two effects occurring here, and I can't name either of them. First of all, there is a hatching pattern in the thin edge of the cirrus clouds where the sun is shining through, most visible on the photo with the carpark and building. I'm not sure how this effect is being caused, whether it's crepuscular rays or different densities of cloud creating the shadows or maybe something completely different.
The other effect is how these clouds are being formed. It looks like this could be a similar process to that which forms fallstreak holes. The alto/cirrocumulus seems to be freezing from supercooled water to ice in a chain reaction, like what one might expect to see at a fallstreak hole. In this instant, the clouds to the west where the sun is setting are all cirrus and evidently composed of ice and all the clouds to the east are alto/cirrocumulus and composed of liquid water, perhaps supercooled water.
How can liquid water be below 0°c?
The liquid water forming the alto/cirrocumulus clouds is supercooled, meaning it is below 0°c but hasn't frozen to ice as it requires freezing nuclei. Freezing nuclei may be introduced by other ice particles for example, which explains how this process creates a chain reaction that spreads through the cloud.
How come it's freezing and not evaporating?
The alto/cirrocumulus appears to be freezing rather than evaporating here as the cirrus clouds can be seen at the same or maybe even lower altitude than the layer of cumulus. These cirrus clouds fill in the gap around the alto/cirrocumulus cloud and seem to be growing from it, much like the effect seen with a fallstreak hole.
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