An Investigation of Turbulence and Microphysical Variations Within Winter Storms as Identified by Enhanced Spectrum Width Layers from a Ka-Band Radar

It is hypothesized that winter storms have numerous in-cloud turbulent regions that enhance microphysical growth, but the lack of high spatio-temporal observations have hindered investigations of winter-time mesoscale and microscale features. The Ka-Band Scanning Polarimetric Radar (KASPR) at Stony Brook University is ideally suited to sample these features, with a 1s sampling rate paired with spatial resolutions of 15m and 35m for the vertical profiles and PPI scans, respectively. KASPR was operating from 2017-2021, in part with the NASA Investigation of Microphysics and Precipitation of Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign in 2020. KASPR often observes enhanced Doppler spectrum width layers (SWLs) during winter storms, which can result from regions of turbulence or variations in microphysics. The generation of these layers is explored using KASPR VAD wind data, nearby soundings and analyses, and the KASPR dual polarimetric data.

A two-dimensional convolution-based feature recognition algorithm was developed to identify SWLs using vertically pointing profiles and PPI scans. From 2017-2021, ~83,000 (~56,000) SWLs were identified from 50hr (178hr) of PPI scans (vertical profiles). Preliminary results reveal that the majority of SWLs are <100m thick and persist for <30s, but ~12% of SWLs are >250m thick and persist >30s. The peak altitude for these SWLs is 2-3 km, which is often near the location of peak warm air advection and veering wind in these storms. SWL frequency, thickness, and magnitude variations will be related to vertical wind shear (via VAD profile), thermodynamic profiles, and dual-pol microphysical data. These SWLs will be linked to storms observed during IMPACTS, as well as related to the cyclone center as it passes the region. Manual inspection of the radar data will also relate SWLs to any snow bands, generating cells, gravity waves, or turbulent eddies (K-H waves).