California's Park Fire Bears Hallmark Of The New Fire Regime We Face - Pyrocumulonimbus Clouds

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With 600 square miles burned so far, the Park Fire is already one of California’s biggest wildfires ever — and it’s still far from contained. Driven by strong winds, the blaze has chewed through desiccated plants, spewing smoke high into the atmosphere. So much smoke and rising hot air, in fact, that it’s been creating fire tornados and one of the strangest natural phenomena on earth: the pyrocumulonimbus cloud, or pyroCb.

It’s a smoke thundercloud that makes a dangerous wildfire like the Park Fire, burning in the northern part of the state, even more unpredictable. PyroCbs can produce lightning that goes on to spark more fires around the very blaze that made the clouds. And as the planet warms, pyroCbs seem to be growing more common, since they’re spawned by the biggest, fiercest wildfires, which themselves are getting worse. “PyroCbs are such massive, almost volcanic-like eruptions,” said Rajan Chakrabarty, an aerosol scientist who studies the clouds at Washington University in St. Louis. “These pyroCbs create their own fire weather.”

The Park Fire has grown massive on a diet of extra-dry fuel. This part of California hasn’t burned for decades, so a lot of plant life had built up and desiccated under the summer sun. Very low humidity has helped suck what little moisture remains in the vegetation, turning the landscape into a pile of tinder. Such a big and intense fire is a breeding ground for pyroCbs — marvels of fire physics. As a blaze like the Park Fire burns — and burns more viciously thanks to climate change producing higher temperatures and drier fuels — the heat from the flames rises, propelling smoke particles tens of thousands of feet into the atmosphere. As the air rises, it cools and expands. Water then condenses on the smoke particles, and the cloud forms.

The masses of rising air in a pyroCb form a sort of void at ground level, which sucks in more air, generating winds that encourage the spread of the flames. The most intense of wildfires consume so much oxygen that they can somewhat smother themselves, but pyroCb winds inject more of the gas into the firestorm. It’s “a self-perpetuating process,” said Daniel Swain, a climate scientist at ​​UCLA and the National Center for Atmospheric Research. “Because the more intense it is, the more oxygen that rushes in, which means the more intense it is, which means the more oxygen rushes in. So you can see how that goes.”

EDIT

https://grist.org/science/california-park-fire-spawning-smoke-thunderclouds-pyrocumulonimbus/