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Cloud Burning!

May 17th, 2007 by Jamison A. Smith, Ph. D. · 1 Comment

I was writing a preapplication for a proposal last week, so I had to review
a bunch of literature. I found a fun one that one of my collaborators wrote
a while back on “cloud burning.”

Ackerman et al., “Reduction of tropical cloudiness by soot,” Science 288,

Generally, aerosol particles are thought to cool the Earth through the direct
and indirect aerosol effects on climate, but this generalization does not
always hold. If the aerosol particles are strongly absorbing such as soot,
then other things occur.

In this paper, the authors show that soot inclusions in aerosol particles
increase the speed of clouds “burning off” once the sun rises. In addition,
the absorption stablizes the boundary layer, inhibiting later convection.
This reduction in reflective cloud warms the Earth.

I think this phenomena later became termed the semi-direct effect to
distinguish it from the direct and indirect aerosol effects on climate.

Tags: aerosols · climate

1 response so far ↓

  • 1 Andy Ackerman // Jun 4, 2007 at 4:19 pm

    Regarding the terminology “semi-direct” effect — Hansen actually coined the term on p. 6858 of a JGR paper published in 1997, but unfortunately Ackerman et al. did not learn of it until after their paper was published.

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