Manifestation of Elevated Convection in Wintertime Extratropical Cyclones During IMPACTS

During the 2020, 2022, and 2023 IMPACTS field campaign wintertime cyclones and frontal cases were sampled. Past studies on wintertime extratropical cyclones east of the Rocky Mountains and case studies from IMPACTS have shown that elevated convection occurs near the low-pressure center within the comma head. These studies found that elevated instability within the comma head develops when warm, dry air associated with the dry slot descends above the low-pressure center. However, how common elevated convection is and its characteristics such as the depth and strength of the unstable layer, the depth of the stable layer beneath it, and the strength of the vertical circulations associated with the instability is not understood. This work uses X-band and W-band radar data from IMPACTS and RAP reanalysis data from IMPACTS cases that had a defined low-pressure center and data was gathered within the comma head of the cyclone. For each flight leg, equivalent potential temperature (θ_e) from RAP was overlayed on radar vertical cross sections to identify when θ_e decreased with height and was co-located with convective towers. To determine the depth and magnitude of the unstable and stable layer, the height and θ_e at the base of the unstable layer, the height of the equilibrium level, the height and θ_e at the lowest θ_e value, and the height and θ_e at the surface were recorded. Radar echo top and contour frequency by altitude diagrams of radial velocity were analyzed to determine how cloud top height and vertical circulations relate to the unstable layer. Each cyclone was categorized based on type and the strength of the pressure gradient over 200 km from its center. These characteristics were statistically analyzed to determine how common elevated convection is, how elevated convection manifests in wintertime cyclones, and if its characteristics vary depending on cyclone type and strength.