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How aerosol formation helps brighten clouds, balance climate

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How aerosol formation helps brighten clouds, balance climate

Small aerosol particles help in “brightening” of clouds, enabling them to alter Earth’s radiative balance and ultimately its climate, according to a study led by the Cooperative Institute for Research in Environmental Sciences (CIRES).

When deep, convective clouds in the tropics carry gases high into the atmosphere, they form small aerosol particles in a process called gas-to-particle conversion. As they condense, they grow big enough to brighten lower-level cloud in the lower troposphere.

This gas-to-particle conversion brightens clouds in the tropics over both the Pacific and Atlantic Oceans, according to the study published in the journal Nature.

“That’s important since brighter clouds reflect more energy from the sun back to space,” said Christina Williamson, a CIRES scientist and the paper’s lead author.

Further, this formation of new particle covers about 40 per cent of the Earth’s surface, which means some of the current climate models underestimate the cooling impact of some clouds, according to the study.

“Understanding how these particles form and contribute to cloud properties in the tropics will help us better represent clouds in climate models and improve those models,” Williamson said.

Source: Christina Williamson, Nature. 

For the study, the team took global measurements of aerosol particles from American National Aeronautics and Space Administration (Nasa) Atmospheric Tomography Mission, or ATom, which conducted a field campaign that spanned the Arctic to the Antarctic over a three-year period.

In the ATom, a fully instrumented Nasa DC-8 aircraft flew four times over the Pacific and Atlantic Oceans from near sea level to an altitude of about 12 km, for 26-days. It continuously measured greenhouse gases, other trace gases and aerosols.

The findings showed that in remote places with cleaner air, the effect of aerosol particle formation on clouds was found to be much larger,

The study can improve the effect of aerosols and clouds on radiation in climate models. “We want to properly represent clouds in climate models,” Williamson said.

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