Preprints
https://doi.org/10.5194/acp-2021-1001
https://doi.org/10.5194/acp-2021-1001

  09 Dec 2021

09 Dec 2021

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

A Lagrangian Analysis of Pockets of Open Cells over the Southeast Pacific

Kevin M. Smalley1, Matthew D. Lebsock1, Ryan Eastman2, Mark Smalley1,3, and Mikael Witte1,3,4 Kevin M. Smalley et al.
  • 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
  • 2Department of Atmospheric Sciences, University of Washington, Seattle, Washington
  • 3Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, California
  • 4Naval Postgraduate School, Meteorology, Monterey, California, USA

Abstract. Pockets of open cells (POCs) have been shown to develop within closed-cell stratocumulus (StCu) and a large body of evidence suggests that the development of POCs result from changes in small-scale processes internal to the boundary layer rather than large-scale forcings. Precipitation is widely viewed as a key process important to POC development and maintenance. In this study, GOES-16 satellite observations are used in conjunction with MERRA-2 winds to track and compare the microphysical and environmental evolution of two populations of closed-cell StCu selected by visual inspection over the southeast Pacific Ocean: one group that transitions to POCs and another control group that does not. The high spatio-temporal resolution of the new GOES-16 data allows for a detailed examination of the temporal evolution of POCs in this region. We find that POCs tend to develop near the coast, last tens of hours, are larger than 104 km2, and often (88 % of cases) do not re-close before they exit the StCu deck. Most POCs are observed to form at night and tend to exit the StCu during the day when the StCu is contracting in area. Relative to the control trajectories, POCs have systematically larger effective radii, lower cloud drop number concentrations, comparable conditional in-cloud liquid water path, and a higher frequency of more intense rainfall. Meanwhile, no systematic environmental differences other than boundary-layer height are observed between POC and control trajectories. These results support the consensus view regarding the importance of precipitation on the formation and maintenance of POCs and demonstrate the utility of modern geostationary remote sensing data in evaluating POC lifecycle.

Kevin M. Smalley et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on acp-2021-1001', Kevin Smalley, 10 Jan 2022
  • CC2: 'Comment on acp-2021-1001', Kevin Smalley, 11 Jan 2022
  • RC1: 'Comment on acp-2021-1001', Anonymous Referee #1, 17 Jan 2022
  • RC2: 'Comment on acp-2021-1001', Anonymous Referee #2, 20 Jan 2022

Kevin M. Smalley et al.

Kevin M. Smalley et al.

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Short summary
We use geostationary satellite observations to track pockets of open-cell stratocumulus (POCs) and analyze how precipitation, cloud microphysics, and the environment change. Precipitation becomes more intense, corresponding to increasing effective radius and decreasing number concentrations, while the environment remains relatively unchanged. This implies changes in Cloud Microphysics are more important than the environment to POC development.
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