Precipitation Growth Processes in the Comma-Head Region of the 7 February 2020 Northeast Snowstorm: Results from IMPACTS

Megan M. Varcie, Troy J. Zaremba, Robert M. Rauber, Greg M. McFarquhar, Joseph A. Finlon, Lynn A. McMurdie, Alexander Ryzhkov, Martin Schnaiter, Emma Järvinen, Fritz Waitz, David J. Delene, Michael R. Poellot, Matthew L. Walker McLinden, Andrew Janiszeski

Research output: Contribution to journalArticlepeer-review


On 7 February 2020, precipitation within the comma-head region of an extratropical cyclone was sampled remotely and in situ by two research aircraft, providing a vertical cross section of microphysical observations and fine-scale radar measurements. The sampled region was stratified vertically by distinct temperature layers and horizontally into a stratiform region on the west side, and a region of elevated convection on the east side. In the stratiform region, precipitation formed near cloud top as side-plane, polycrystalline, and platelike particles. These habits occurred through cloud depth, implying that the cloud-top region was the primary source of particles. Almost no supercooled water was present. The ice water content within the stratiform region showed an overall increase with depth between the aircraft flight levels, while the total number concentration slightly decreased, consistent with growth by vapor deposition and aggregation. In the convective region, new particle habits were observed within each temperature-defined layer along with detectable amounts of supercooled water, implying that ice particle formation occurred in several layers. Total number concentration decreased from cloud top to the 288C level, consistent with particle aggregation. At temperatures. 288C, ice particle concentrations in some regions increased to.100 L21, suggesting secondary ice production occurred at lower altitudes. WSR-88D reflectivity composites during the sampling period showed a weak, loosely organized banded feature. The band, evident on earlier flight legs, was consistent with enhanced vertical motion associated with frontogenesis, and at least partial melting of ice particles near the surface. A conceptual model of precipitation growth processes within the comma head is presented.

Original languageEnglish (US)
Pages (from-to)3-29
Number of pages27
JournalJournal of the Atmospheric Sciences
Issue number1
StatePublished - Jan 2023


  • Cloud microphysics
  • Extratropical cyclones
  • Snowbands

ASJC Scopus subject areas

  • Atmospheric Science


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