Physics Colloquium - Dr. Israel Silber of Penn. State University

will give a talk on "Observations of Highly Supercooled Drizzle Over Antarctica: A Unique Event or a Prevalent Phenomenon?" on Tuesday, January 28 at 11:00am in Fisher Hall 138.

Abstract: Comprehensive knowledge of the lifecycle of polar stratiform clouds is crucial for the evaluation of their significant radiative impact on the surface energy budget. A cloud’s lifecycle is determined by a set of complex interactions and feedbacks between different micro- and macro-physical processes. When these polar clouds are highly supercooled, temperature-dependent processes such as heterogeneous ice nucleation result in a dominant role of ice-phase processes in determining the cloud evolution. Indeed, the literature record only brief and spatially limited observations of drizzle in clouds with temperatures below -20°C. In this talk, I will present observations of persistent formation and precipitation of drizzle drops in a cloud at temperatures below -25°C. This drizzle event was observed at McMurdo Station, Antarctica during the Atmospheric Radiation Measurement West Antarctic Radiation Experiment campaign, and lasted for more than 7.5 hours. I will describe the remote-sensing measurements used to detect the drizzle and show the results of large-eddy simulations initialized with two-moment microphysics used to examine the activated ice nucleating particles (INP) and accumulation mode aerosol number concentrations supporting such persistent drizzle formation. My simulation results indicate that liquid-dominated micro-physical processes may frequently occur in highly supercooled stratiform clouds in clean polar environments. Finally, I will briefly describe the utilization of this drizzling event as a test case for climate models in a single column model (SCM) mode.

Bio: Dr. Silber is an assistant research professor at Pennsylvania State University. His work focuses on polar cloud processes from an observational and modeling perspective, and the evaluation of the representation of various cloud processes in large-scale models. Before his main research interests “precipitated” to clouds in the lower atmosphere, he completed his Ph.D. at Tel-Aviv University where he studied the coupling between the aeronomy of the middle atmosphere and the ionospheric base.

Tuesday, January 28 at 11:00 a.m. to 12:00 p.m.

Fisher Hall, 138
1400 Townsend Drive, Houghton, MI 49931

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Department of Physics


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