VORTEX 2: Storm-scale Baroclinity Using Fine-scale Observations and Numerical Models

Texas Tech University, Lubbock TX

Investigators

Abstract

This award is one component of a mutli-investigator effort known as the Verification of the Origins of Rotation in Tornadoes Experiment 2 (VORTEX 2). VORTEX 2 is a follow on to VORTEX 1 whose field phase was conducted during the Spring of 1994 and 1995. The VORTEX 1 advanced knowledge of the kinematic structures of tornadic and nontornadic storms and provided some hints as to the sensitivity of the evolution of supercell storms and tornadogenesis to very fine spatial scale heterogeneity. The VORTEX 2 research objectives will focus on the genesis and maintenance of tornadoes and on the structure of the near wind field of the tornado. The VORTEX 2 is being conducted in conjunction with the National Oceanic and Atmospheric Administration and it will involve an unprecedented observational network of stationary and mobile facilities that include Doppler radars, surface and upper air observations. . Supercell thunderstorms are known to contain potentially significant thermodynamic and kinematic gradients, many of which are suspected to be relevant to low-level mesocyclogenesis. Owing to the strong gradients in virtual potential temperature that have been resolved in prior numerical studies, storm-scale baroclinity is suspected to play a role in the baroclinic generation of horizontal vorticity, which can be tilted and stretched by the principal updraft of the storm in some circumstances. Though the relatively sparse in-situ observations gathered in the field to this point have shed some light on the issue of baroclinity, these observations are typically poor in spatial resolution. The intellectual merit of the research under this award follows from the introduction of newly-developed "StickNet" technology, an array of rapidly-deployable surface stations. These systems will be deployed during VORTEX 2 to address the issue of storm-scale baroclinity both from the standpoint of tornadogenesis and the verification/improvement of storm-scale numerical weather prediction models. These measurements will provide unprecedented detail of variations in thermodynamic and kinematic quantities in close proximity to supercell mesocyclones which, in combination with air parcel trajectories calculated from dual-Doppler analyses and numerical models, will permit the construction of a vorticity budget for air parcels entering the low-level mesocyclone. StickNet measurements will also provide insight into what properties of multi-storm interactions are favorable to tornadogenesis and tornado maintenance. The StickNet data also will be used to validate numerical storm-scale models and also will provide a basis for verification and improvement of existing methods of thermodynamic retrieval techniques. The broader impacts of the study will be felt in a number of ways. A number of graduate and undergraduate students will be utilized in the planning and execution of StickNet data collection. Some of these students have background in fields other than meteorology (e.g., wind engineering), and therefore will have the opportunity to expand their knowledge base. Given the typical ethnic diversity of the student population at Texas Tech University, it is expected that traditionally underrepresented groups, particular those of Hispanic descent, will have full opportunity to participate in the StickNet component of VORTEX2. The ultimate goal of the research is the improvement of severe thunderstorm and tornado forecasts, both through real-time observation and short-term numerical modeling. This increase in forecast skill is of utmost importance for the protection of life and property. Through the broad dissemination of research results in journal publications and conference presentations, all research objectives that are met will have significant impact in the community.