Preprints
https://doi.org/10.5194/acp-2021-586
https://doi.org/10.5194/acp-2021-586

  19 Jul 2021

19 Jul 2021

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

Updraft dynamics and microphysics: on the added value of the cumulus thermal reference frame in simulations of aerosol-deep convection interactions

Daniel Hernandez-Deckers1, Toshihisa Matsui2, and Ann M. Fridlind3 Daniel Hernandez-Deckers et al.
  • 1Grupo de Investigación en Ciencias Atmosféricas, Departamento de Geociencias, Universidad Nacional de Colombia, Bogotá, Colombia
  • 2NASA Goddard Space Flight Center, Greenbelt, USA
  • 3NASA Goddard Institute for Space Studies, New York, USA

Abstract. One fundamental question about atmospheric moist convection processes that remains debated is whether or under what conditions a relevant variability in background aerosol concentrations may have a significant dynamical impact on convective clouds and their associated precipitation. Furthermore, current climate models must parameterize both the microphysical and the cumulus convection processes, but this is usually implemented separately, whereas in nature there is a strong coupling between them. As a first step to improve our understanding of these two problems, we investigate how aerosol concentrations modify key properties of updrafts in eight large-eddy permitting regional simulations of a case study of scattered convection over Houston, Texas, in which convection is explicitly simulated and microphysical processes are parameterized. Dynamical and liquid-phase microphysical responses are investigated using two different reference frames: static cloudy-updraft grid cells versus tracked cumulus thermals. In both frameworks we observe the expected microphysical responses to higher aerosol concentrations, such as higher cloud number concentrations and lower rain number concentrations. In terms of the dynamical responses, both frameworks indicate weak impacts of varying aerosol concentrations relative to the noise between simulations over the observationally derived range of aerosol variability for this case study. On the other hand, results suggest that analysis of thermals can provide a better pathway to sample the most relevant convective processes. For instance, vertical velocity from thermals is significantly higher at upper levels than when sampled from cloudy-updraft grid points, and several microphysical variables have higher average values in the cumulus thermal framework than in the cloudy-updraft framework. In addition, the thermal analysis is seen to add rich quantitative information about the rates and covariability of microphysical processes spatially and throughout tracked thermal lifecycles, which can serve as a stronger foundation for improving subgrid-scale parameterizations. These results suggest that cumulus thermals are more realistic dynamical building blocks of cumulus convection, acting as natural cloud chambers for microphysical processes.

Daniel Hernandez-Deckers et al.

Status: open (until 30 Aug 2021)

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

Daniel Hernandez-Deckers et al.

Daniel Hernandez-Deckers et al.

Viewed

Total article views: 189 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
125 62 2 189 4 2
  • HTML: 125
  • PDF: 62
  • XML: 2
  • Total: 189
  • BibTeX: 4
  • EndNote: 2
Views and downloads (calculated since 19 Jul 2021)
Cumulative views and downloads (calculated since 19 Jul 2021)

Viewed (geographical distribution)

Total article views: 188 (including HTML, PDF, and XML) Thereof 188 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 28 Jul 2021
Download
Short summary
We investigate how the concentration of aerosols (small particles that serve as seeds for cloud droplets) affect the dynamics of simulated clouds using two different frameworks: the traditional selection of cloudy rising grid points, and tracking small-scale coherent rising features (cumulus thermals). By doing so, we find that these cumulus thermals reveal useful information about the coupling between internal cloud circulations and cloud droplet and rain drop formation.
Altmetrics