These jellyfish clouds drifted in the air currents over Portland, Oregon, US, where they were spotted by Robin Cole (Member 44,966). The tendril-like streaks hanging from them are known as virga. They are in fact showers falling from clumps of the mid-level cloud called Altocumulus. There is no sting in these celestial tendrils. Instead, they’re filled with tiny, tumbling crystals of ice.
The cloud trails are known as virga rather than precipitation because they never reach the ground. Since Altocumulus clumps are quite high up – the ones here might be up at around 4 miles (6 km) – there’s plenty of atmosphere for the ice to fall through before reaching the ground. Often the air below the Altocumulus is warm and dry enough for the ice crystals to evaporate away as they descend. This change of state from ice to invisible gas, water vapour, is known as ‘sublimation’.
How easy is easy to forget that our atmosphere is an ocean of gasses – one that is similar to, and intimately linked with, its watery cousins like the Pacific and the Atlantic below. Easy to forget also that we are creatures of the deep, our daily dramas playing out right down on the ocean bed. When a shoal of virga cloud jellyfish drifts into vision like this, it comes to remind us we live within the sky not beneath it.
Altocumulus with virga spotted over Portland, Oregon, US by Robin Cole (Member 44,966).