Characteristics of Layers of Enhanced Spectrum Width within Northeast U.S. Winter Precipitation Events

A Ka-Band Scanning Polarimetric Radar (KASPR) at Stony Brook University on Long Island, New York (NY), is used to investigate shear and turbulent layers in winter precipitation events, which are often revealed as Doppler spectrum width (SW) layers (SWLs). This study provides the first climatology of SWLs in winter precipitation events from 2017 to 2021 by documenting their spatial and kinematic characteristics. Three events are presented to introduce these structures in different winter precipitation environments. A percentile-based detection algorithm was developed to automatically identify SWLs in plan position indicator (PPI) scans, and a velocity–azimuth display (VAD) technique is applied to decompose the flow into resolved and unresolved components, from which proxies for shear and turbulence are derived. A binary operator is used to conjoin SW enhancements exceeding the 75th percentile into individual SWLs. The algorithm identified 77 955 SWLs in KASPR PPI scans over four winter seasons. Most SWLs are thin (<200 m) and occur preferentially between 0.6 and 0.9 of cloud depth. SWL magnitudes are generally weak but occasionally exceed 3 m s^-1, and azimuthal spans are typically narrow (<90°). Resolved shear is most closely associated with SWLs, while unresolved velocity (turbulence proxy) is not preferentially concentrated within SWLs. However, when a shear-organized SWL is present, unresolved velocity exerts the primary control on its thickness and magnitude, with resolved shear playing a secondary role. Given the ubiquitous nature of these SWLs, they may be important features for understanding subkilometer-scale dynamic processes in winter precipitation.