Behind the Forecast: How deserts influence cloud formation

LOUISVILLE, Ky. (WAVE) - Cirrus clouds are thin, wispy, high-level clouds that resemble cotton candy threads. While ice crystals make up cirrus clouds, some of the driest and hottest parts of our planet may play a significant role in their formation.

Several billion tonnes of dust are thrown into the atmosphere from our planet’s driest regions each year, making dust one of the most ubiquitous aerosol particles.

For clouds to form, condensation nuclei, like dust, are needed. A recent airborne atmospheric sampling mission, the largest ever, found that dust-initiated cirrus clouds accounted for “34 to 71% of all cirrus clouds outside of the tropics.” While the Sahara Desert emits the most dust, researchers found that Central Asian deserts were vital sources for cirrus cloud formation.

The research team circumnavigated the planet four times between 2016 and 2018 with a specialized and custom-built single-particle mass spectrometer called PALMS. PALMS ingested particles one at a time and analyzed their chemical signatures. Researchers found continental dust in every latitude and altitude. Research and modeling found that the atmospheric environment downwind of deserts was more significant for the formation of cirrus clouds than just the dust itself.

While the Sahara Desert’s dust makes up 60% of the planet’s dust emissions, only a small amount of it was pushed high enough into the atmosphere to seed the ice crystals needed to make cirrus clouds. The Asian Summer Monsoons and dry convections were found to lift Central Asian dust higher into the atmosphere more effectively.

This research is vital because of the role clouds play in our climate. While cumulus clouds (the puffy, white clouds) have a net cooling effect due to their ability to reflect sunlight, cirrus clouds have a net warming effect by trapping heat that would’ve been released into space.

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