While Chicagoans are experiencing very pleasant weather, wildfires are raging in California, Oregon and Northwest Canada.
The fires are producing more than clouds of smoke and ash. They are causing astonishing cloud formations called pyrocumulus clouds. They are also known as “fire clouds. ”
Fire clouds are similar to the classic cauliflower-topped cumulus clouds, but the heat that forces the updraft (which leads to cooling and condensation of water vapor) comes from fires or volcanic activity instead of sun-warmed ground. If you are interested, you can also read more about cumulus clouds here.
Thunderstorm-producing fire clouds are called pyrocumulonimbus clouds. These are the most extreme form of these fire-caused clouds. There can be lightning, which can ignite more fires. Water clinging to the ash particles suspended in the clouds can fall as rain, sometimes extinguishing the fires that produced them!
Those ash particles act as cloud condensation nuclei. For this reason, fire clouds are of interest for research into cloud-seeding. According to Weatherquestions.com—
Cloud condensation nuclei (CCN) are aerosols that act as the initial sites for condensation of water vapor into cloud droplets or cloud ice particles. Virtually all cloud droplets or ice particles originate around some sort condensation nuclei which tend to “attract” water.
Those burning wildfires are also responsible for the colorful sunsets people are seeing here in the Midwest and Northeast.
As Tom Skilling explains, the smoke from the wildfires has been carried here by prevailing northwesterly winds, the jet stream winds that have kept us cool all summer. The suspended ash particles are acting as a filter, screening out the higher frequency blues in the spectrum of sunlight. The red, orange and yellow colors come through, resulting in firey sunrises and sunsets.
If you are concerned about the smoke in the air, AccuWeather mentions the smoke is originating too far away and occurring too high in the atmosphere to significantly affect air quality. It should not bother people with respiratory problems.
In addition, the lower humidity may improve observing conditions for the Perseid meteors and the big bright moon. You can read more about that here.
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