Abstract
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 by investigating the effects of aerosol loading on the latent heating and vertical motion profiles of warm rain. 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.
Highlights
Aerosol–cloud interactions remain one of the largest sources of uncertainty in future climate projections (Boucher et al, 2013)
Unlike studies that focus on the suppression of drizzle in shallow warm clouds, such as Ackerman et al (2004), which found increased turbulence through suppression of drizzle by aerosol, we evaluate the effects of aerosol on warm rain events and define invigoration beyond just an increase in turbulence or vertical motion but by changes in the latent heating structure throughout the cloud layer
Using latent heating and vertical motion profiles from the Wisconsin Algorithm for Latent heating and Rainfall Using Satellites (WALRUS), we show that there is a discernible signal of invigoration in warm clouds due to aerosol
Summary
Aerosol–cloud interactions remain one of the largest sources of uncertainty in future climate projections (Boucher et al, 2013). Their role in climate feedbacks, how they affect low clouds, controls the magnitude of the climate sensitivity (Zelinka et al, 2020). Invigoration, or the enhanced size, depth, precipitation rate, or turbulence, of low clouds was hypothesized as a potential outcome of aerosol–cloud interactions decades ago but remains relatively unconfirmed from observations (Pincus and Baker, 1994; Rosenfeld et al, 2008). Invigoration of warm cloud structure has the potential to alter deep convection, making eventual storms more intense and turbulent (Chen et al, 2017). Unlike studies that focus on the suppression of drizzle in shallow warm clouds, such as Ackerman et al (2004), which found increased turbulence through suppression of drizzle by aerosol, we evaluate the effects of aerosol on warm rain events and define invigoration beyond just an increase in turbulence or vertical motion but by changes in the latent heating structure throughout the cloud layer
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
