An exploration of kinematic wind fields derived from Doppler velocity retrievals from airborne conically scanning radar observations of snowbands during IMPACTS 2020

Winter storms over the northeastern United States often exhibit narrow bands of heavy snowfall within broader areas of lighter precipitation. These are called snowbands, and several dynamical processes are thought to be important in their formation and maintenance. Frontogenesis resulting from convergence, rotation, and deformation of the horizontal wind field, often in regions of conditional or weak moist symmetric instability, has been historically associated with the largest primary snowbands. However, smaller multi-bands may be caused by elevated convection, generating cells, gravity waves, or other processes involving narrow regions of vertical motion that lift warm, moist air to a level where it saturates and precipitation forms. During winter 2020, the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign sampled cloud microphysics, thermodynamics, and dynamical processes in multiple storm events by collecting both in-situ and remotely sensed aircraft-based observations. Using Velocity-Azimuth Display (VAD) analysis on the Doppler velocity retrievals captured by the conically scanning ER-2 X-band Radar (EXRAD) flown on the high-altitude ER-2 aircraft, we can uncover kinematic processes acting on the background wind field in the vicinity of snowbands. We use this data together with radar reflectivity and Doppler velocity retrievals from the WSR-88D network to explore how the dynamics of the mesoscale flow relate to areas of enhanced snowfall observed during a particularly strong storm on 7 February 2020. The ER-2 flew west-east flight legs oriented perpendicularly across a sloping frontal boundary associated with the storm, and the retrieved winds from the VAD analysis clearly show the low-level northerly winds switch to higher-level strong southerly winds aloft. The total deformation calculated from the retrieved winds is maximum above the frontal boundary coincident with a local region of higher reflectivity. This presentation explores the relationships between regions of enhanced deformation and frontogenesis from EXRAD wind retrievals and observed microphysical properties from in-situ aircraft observations and surface snowfall reports throughout the development of the 7 February 2020 event.