Kinematic Modeling Study of the Re-Organization of Snowfall beneath Cloud-top Generating Cells in Midlatitude Cyclones
While past research of midlatitude winter cyclones has investigated both near-surface precipitation bands and cloud top generating cells within the comma head region of such storms, little is known about the relationship between the two. The work aims to determine the role of kinematics in re-organizing ice particles beneath cloud top generating cells into environments favorable for near-surface precipitation bands using a kinematic model.
A series of experiments tested the role of deformation on particle re-organization. Particle clusters representative of cloud top generating cells were arranged in rows, given different cluster row spacings and a residence time (tr) in which they fall through the grid subject to stretching deformation flow. Particle plumes subject to maximum deformation, maximum tr, and minimum row spacing exhibited a congealed linear shape stretched along the axis of dilatation at the surface.
Another set of experiments used 2-D convergent flow for three different banding cases. Cross-sections were drawn normal to the long axis of the observed band(s) and using HRRR model initialization winds, along cross-sectional flow was calculated. Ice particles were spaced uniformly atop the grid and given similar tr to previous experiments. Histograms of particle concentration showed near-surface ice particles distributions with ice particle maxima collocated near the observed band(s).
The last set of experiments using 3-D winds from the HRRR model initialization winds, tests the effects of both convergent and deformation flow on particles, uniformly distributed atop the grid with similar tr. Preliminary results show concentration increases near a low-level observed reflectivity band.