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Effects of wind shear and aerosol conditions on the organization of precipitating marine stratocumulus clouds
  • Jong-Hoon Jeong,
  • Mikael K Witte,
  • Mark Smalley
Jong-Hoon Jeong
Jet Propulsion Laboratory, California Institute of Technology, Joint Institute for Regional Earth System Science and Engineering, University of California

Corresponding Author:[email protected]

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Mikael K Witte
Department of Meteorology, Naval Postgraduate School, Jet Propulsion Laboratory, California Institute of Technology, Joint Institute for Regional Earth System Science and Engineering, University of California
Mark Smalley
Jet Propulsion Laboratory, California Institute of Technology, Joint Institute for Regional Earth System Science and Engineering, University of California

Abstract

This study examines how wind shear affects precipitating marine stratocumulus clouds under different cloud droplet number concentrations (Nd). We performed a series of large eddy simulations (LES) of nocturnal marine stratocumulus clouds using Cloud Model 1 (CM1). The simulations show that Nd is the dominant factor for cloud cellular organization in this cloud regime rather than wind shear. Low Nd characterizes the open cellular structure with a high in-cloud liquid water path (LWP). When wind shear is increased, the cloud fraction tends to decrease along with LWP, suggesting the cloud top region is significantly influenced by the entrainment and mixing of dry air from the free troposphere. We also examine cold pools in open and closed cellular clouds. Open-cell clouds produce larger and deeper cold pools compared to closed-cell clouds. Interestingly, cold pools can exist without surface precipitation and are produced by evaporation of light precipitation (drizzle) below the cloud base with weak downdrafts. The evaporation of raindrops and drizzle play an important role in initiating new convection, particularly where colliding outflows occur downstream of the cloud. This secondary convection contributes to the development and maintenance of the cloud cellular organization and formation. 
30 Sep 2023Submitted to ESS Open Archive
17 Oct 2023Published in ESS Open Archive