Atmospheric Sightings

Our planet’s atmosphere, fragile and proportionately thin as the skin of an apple, is not living its best life right now. In my part of the world – western Canada – hundreds of wildfires have filled the air with grey-orange smoke for over a month, and the hot and bone-dry conditions show no sign of letting up. The only star I see these days is an angry red Sun. It’s an ominous sight, but still strangely beautiful as the fine smoke particles strongly scatter blue light out of the line of sight. Others have bigger problems than I, of course, but I do have a long list of astrophotography projects on hold. A good night of stargazing may still be weeks away. Is this the new normal?

 

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The summer ‘monsoons’ have obliterated the stars for the past couple of weeks and at least for one week more. But a good stargazer still needs to look up from time to time, which is how I found a formation of mammatus clouds passing overhead after an afternoon and evening of heavy thunderstorms near Calgary, Canada.

These ominous and distinctively shaped clouds are usually formed on the underside of anvil-shaped cumulonimbus clouds that cause severe thunderstorms. These sagging pouches are mostly made of ice crystals. An individual “pouch” can range anywhere from one to three kilometers in diameter, and a mammatus cloud field can stretch for dozens of kilometers across the sky.

Their formation is still poorly understood, but they may form from cold, dense air sinks toward the earth from higher up. This sinking air pokes through the bottom of the anvil resulting in the pouch-like appearance. So they may be a rare occurrence of cloud formation caused by sinking air rather than rising air. The cloud droplets and ice crystals eventually evaporate and the mammatus clouds dissipate. These clouds were passing quickly and moved over the horizon before they faded away.

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