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.
During the spring seasons of 2009 and 2010, Texas Tech University joined a number of other universities and federal laboratories to participate in the Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX2). The overarching goal of VORTEX2 is to better understand how thunderstorms produce tornadoes, allowing for the improvement in the accuracy of tornado warnings. A number of theories exist on how exactly tornadoes form, and it is almost certain that many dynamic mechanisms are acting concurrently to ultimately influence the success or failure of tornado development. One specific aspect of tornadogenesis that was addressed in this study relates how sharp horizontal changes in air density within the parent thunderstorm may be an effective source of rotation for tornadoes. These changes in air density are principally tied to variations in air temperature, though also are dependent on the water vapor and liquid water content of the air. As thunderstorms typically produce a large volume of cold air owing to the evaporation of rainwater and melting of ice, the observations obtained in this study are important for verifying how these processes may ultimately affect tornado development. During the VORTEX2 field phase, Texas Tech University deployed a fleet of unmanned, ruggedized probes ahead of supercell thunderstorms, a specific form of thunderstorm known to produce the great majority of tornadoes. These probes had the capability to make measurements of temperature, humidity, air pressure, and wind speed and direction. In total, 650 probes were deployed over the field period, stretching from Wyoming to Texas. Analysis of these data have yielded the following conclusions for the samples studied thus far: Tornadic thunderstorms tend to show weaker pools of cold air overall, The cold air that is produced in tornadic thunderstorms tends to align more favorably for the generation of rotation of air entering the tornado, and A specific feature evident in radar data for some tornado events, termed the "low reflectivity ribbon" recently, is found to associate with air that is distinctly negatively buoyant. The investigators on this project have further developed a method by which to integrate a diverse set of atmospheric observations into numerical models for the purpose of producing accurate four-dimensional depictions of severe thunderstorms. These simulations have been useful tools in better understanding the evolution of the studied thunderstorms, as related to the genesis (or failure) of tornadoes. The aforementioned simulations have been found to be particularly sensitive to processes describing how rain and hail form and grow, a finding that points again to the importance of better understanding how pools of cold air develop in supercell thunderstorms. Training and outreach activities have been crucial to the success of this project. A number of graduate and undergraduate students at Texas Tech University participated in the data analysis as well as the probe deployment, forecasting, and instrument maintenance. The results from this project have been broadly disseminated to the public through peer-reviewed publications and conference presentations, and have been tightly integrated into the curriculum at various universities. The investigators have also had the opportunity to share these activities and findings with middle-school and high-school students, through tours of the facilities at Texas Tech University, and by way of specific outreach opportunities such as the Hispanic Engineering, Science and Technology Week at the University of Texas-Pan American.
