Manifestation of Elevated Convection in Wintertime Extratropical Cyclones During IMPACTS

During the 2020 and 2022 IMPACTS field campaign 16 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 9 IMPACTS cases where the comma head of a cyclone with a closed low-pressure center was sampled. For each flight leg, equivalent potential temperature (q_e) from RAP was overlayed on radar vertical cross sections to identify when q_e decreased with height and was collocated with convective towers. To determine the depth and magnitude of the unstable and stable layer, the height and q_e at the base of the unstable layer, the height of the equilibrium level, the height and q_e at the lowest q_e value, and the height and q_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.