Highly Supercooled Drizzling Stratus Over Antarctica: A Good Test for Climate Models?
Authors
Israel Silber — Pennsylvania State University
Ann M. Fridlind — NASA - Goddard Institute for Space Studies
Johannes Verlinde — The Pennsylvania State University
Andrew Ackerman — NASA - Goddard Institute for Space Studies
Yaosheng Chen — University of Colorado Boulder
Sheng-Hung Wang — The Ohio State University
David Bromwich — Ohio State University
Maria Paola Cadeddu — Argonne National Laboratory
Edwin W. Eloranta — University of Wisconsin
Category
High-latitude clouds and aerosols
Description
Brief and spatially limited observations of drizzle at temperatures below -20°C have suggested that riming and other temperature-dependent cloud microphysical processes such as heterogeneous ice nucleation and ice crystal depositional growth prevent persistent drizzle formation in the coldest environments. In this study, we report on persistent formation and precipitation of drizzle drops at cloud temperatures below -25°C for a period exceeding 7.5 hours on August 16, 2016, at McMurdo Station, Antarctica, observed during the AWARE field campaign. We conclude that drizzle was likely present in a widespread cloud field, which stretched for more than ~1000 km along the Ross Ice Shelf coast. Large-eddy simulations in a Lagrangian domain with two-moment microphysics constrained by the available remote-sensing observations suggest that activated ice freezing nuclei (IFN) and accumulation mode aerosol number concentrations supporting such persistent drizzle may have been on the order of 0.1 L-1 and 20 cm-3, respectively. By running the same case with the GISS ModelE3 single-column model (SCM), we demonstrate the capabilities and limitations of ModelE3 in representing the sequential development of supercooled liquid in an elevated layer, ice formation and sustained growth during sedimentation, drizzle formation and evaporation below cloud base, and turbulence driven by cloud-top radiative cooling.
