Preprints
https://doi.org/10.5194/acp-2021-446
https://doi.org/10.5194/acp-2021-446

  09 Jun 2021

09 Jun 2021

Review status: this preprint is currently under review for the journal ACP.

Global Evidence of Aerosol-induced Invigoration in Marine Cumulus Cloud

Alyson Douglas1 and Tristan L'Ecuyer2 Alyson Douglas and Tristan L'Ecuyer
  • 1Atmospheric, Oceanic, and Planetary Physics Department, University of Oxford, Sherrington Rd, Oxford OX1 3PU
  • 2Atmospheric and Oceanic Sciences Department, University of Wisconsin-Madison 1225 W Dayton St, Madison, WI 53706

Abstract. Aerosol-cloud-precipitation interactions can lead to a myriad of responses within shallow cumulus clouds including an invigoration response, whereby aerosol loading results in a higher rain rate, more turbulence, and deepening of the cloud layer. However few global studies have found direct evidence that invigoration occurs. The few satellite based studies that report evidence for such effects generally focus on only the deepening response. Here, we show evidence of invigoration beyond a deepening response. Using latent heating and vertical motion profiles derived from CloudSat radar observations, we show precipitating cumulus clouds in unstable, polluted environments exhibit a marked increase in precipitation formation rates and cloud top entrainment rates. However, invigoration is only discernible when the stability of the boundary layer is explicitly accounted for in the analysis. Without this environmental constraint, the mean polluted and pristine cloud responses are indiscernible from each other due to offsetting cloud responses in stable and unstable environments. Invigoration, or suppression depending on the environment, may induce possible feedbacks in both stable and unstable conditions that could subdue or enhance these effects, respectively. The strength of the invigoration response is found to additionally depend on cloud organization defined here by the size of the warm rain system. These results suggest that warm cloud parameterizations must account for not only the possibility of aerosol-induced cloud invigoration, but also the dependence of this invigorated state on the environment and the organization of the rain system.

Alyson Douglas and Tristan L'Ecuyer

Status: open (until 21 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Alyson Douglas and Tristan L'Ecuyer

Alyson Douglas and Tristan L'Ecuyer

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Short summary
When aerosol enter the atmosphere, they interact with the clouds above in what we term aerosol-cloud interactions, and lead to a series of reactions which delays the onset of rain. This delay may lead to increased rain rates, or invigoration, when the cloud eventually rains. We show that aerosol leads to invigoration in certain environments. The strength of the invigoration depends on how large the cloud is, which suggests that it is highly tied to the organization of the cloud system.
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