Examining Supercell Inflow Environments with Doppler Wind Lidar Observations

Since 2016, the National Severe Storms Laboratory (NSSL) has operated mobile scanning doppler wind lidars (DWL) within the inflow of supercell thunderstorms as part of collaborative field projects (mini-MPEX, TORUS, PERiLS, TORUS-LiTE, and LIFT). The research goal of this instrument is to observe the evolution of storm inflow properties to gain a better understanding of the storm environment surrounding an evolving supercell. Various scanning and post-processing techniques to capture the wind profile evolution via DWL observations have been used. Prior to 2022, a velocity azimuth display (VAD) technique was used to retrieve a vertical wind profile every 3-5 minutes using 8 points 20 degrees off zenith. In 2022-23, a continuous scanning mode (CSM) was implemented to retrieve wind profiles as frequent as every 5 seconds. Both of these scanning strategies yielded vertical profiles of derived horizontal winds every ~16 m with the first usable data point around 75 m AGL after filtering based on a signal-to-noise ratio threshold. A new optimal estimation technique (WINDoe) was designed to incorporate colocated rawinsonde observations into the wind retrievals that provide data between the surface and 75 m. Additional collocated observations are used to validate the post processing techniques and output will be compared to previously used methods.

Early analysis of the inflow environments from the pre-2019 supercells show 1) a channel of enhanced inflow narrower than previously thought, 2) potential differences in the inflow strength between tornadic and non-tornadic supercells, and 3) a lack of a constant increase in wind shear in the presence of a constant increase in storm-relative wind. This analysis aims to support these early findings by including the 2022-23 supercells into the analysis. Focus will be placed on the evolution of the near-ground vertical wind shear and on the storm induced environmental modification in both tornadic and non-tornadic storms. To remove environmental trends from the environmental evolution, relevant far-field radiosonde launches or Rapid Refresh (RAP) model-based analysis are used to establish this background trend. Full, surface-based wind profiles will allow for the quantification and time evolution of severe weather forecasting parameters, such as storm-relative helicity, storm-relative winds, etc. Implications of these results on recent studies discussing the relative importance of streamwise vorticity versus storm-relative winds on supercell properties and tornado production will be discussed. Results also will provide an unprecedented look at the near-ground kinematic properties of supercell inflow environments to help validate storm-environment relationships traditionally derived from rawinsonde observations or model analysis profiles.