EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

What drives increased evaporation at cloud top in polluted stratocumulus clouds?

Adele Igel1 and Abigail Williams2
Adele Igel and Abigail Williams
  • 1Department of Land, Air and Water Resources, University of California, Davis, Davis, United States of America (
  • 2Scripps Institute of Oceanography, University of California, San Diego, San Diego, United States of America (

Observations and simulations show that an increase in aerosol concentration typically leads to an increase in liquid water path in precipitating stratocumulus clouds due to precipitation suppression, but once precipitation is fully suppressed, further increases in aerosol concentration typically lead to a reduction in liquid water path due to enhanced evaporation at cloud top. The increased evaporation is typically attributed directly to the presence of smaller, more numerous cloud droplets. However, observations suggest that the evaporation rate is primarily controlled by the entrainment mixing rate rather than the droplet properties at the tops of stratocumulus clouds. As such, aerosol-induced changes to droplet properties should not directly lead to faster evaporation. Our simulations suggest instead that the smaller, more numerous droplets enhance the cloud top maximum radiative cooling rate, which in turn increases the entrainment rate and speeds evaporation. Our results highlight that unlike integrated radiative cooling, maximum radiative cooling continues to increase with increasing liquid water path and remains sensitive to droplet properties at high liquid water path. As such, the role of radiation in driving aerosol-cloud interactions may need additional consideration in the future.

How to cite: Igel, A. and Williams, A.: What drives increased evaporation at cloud top in polluted stratocumulus clouds?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1845,, 2022.

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