Collaborative Research: Investigating Supercell/Tornado Genesis, Structure and Evolution Using Observations and Numerical Models

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The goal of this research is to improve understanding of severe convective storms using numerical models with particular attention to genesis, structure and evolution of supercells and tornadoes in increasingly realistic environmental conditions. Research questions include: 1) Why some supercell-spawned tornadoes are particularly long-lived? 2) How environmental conditions influence tornado genesis, intensity, and longevity? 3) How capping inversions and microphysical makeup influence cold pool strength and the development of low-level rotation in supercell storms?4) How storm interaction and mergers impact tornado genesis?Observations, numerical modeling and data analysis will be used to address the research questions. The methodological approaches build on the Principal Investigators' (PIs) past work including the successful simulation of an intense and long-lived supercell-spawned tornado, simulations of supercell storm environment at 1 km resolution, assimilation of polarimetric radar observations, and coarse-resolution simulations of storm interactions. Observations will be used to guide parameter studies and for data assimilation while modeling will provide consistent and high resolution space and time data sets for analysis and the means to explore controlled parameter spaces. The modeling studies build on advances in model physics, model parallelization/nesting, new methods for initiating sustained storms in the presence of capping inversions, and ensemble Kalman filter based data assimilation methods. The research will take advantage of the availability of computing systems approaching the petascale as well as future systems such as Blue Waters to be deployed at the University of Illinois in 2011 which will be capable of sustaining petaflop performance for weather and storm simulation. Intellectual Merit of Proposal: The work is aimed at increasing the understanding of supercell/tornado genesis, and structure and evolution. Numerical simulation provides a unique approach for testing hypotheses as well as providing complete data sets for analysis and visualization. It also provides a means to simulate multiple scales, namely the supercell and any tornadoes embedded within it. Of particular interest is determining what environmental conditions and what balance of forces are required for simulations of quasi-steady and long-lived supercell-spawned tornadoes. Broader Impacts: The research will potentially improve public warnings. In particular, the PIs will contribute to understanding why some supercell storms produce tornadoes while others do not. Given the upgrade of the WSR-88D radar network that is currently underway, research on the assimilation of polarimetric radar data will provide new insight as to how to best use this data in storm forecasting. Research findings will be communicated via conference presentations, peer-reviewed journal articles and instructional modules for wider use by meteorological education, research and operational communities. The results will be used in classes at the University of Illinois and University of North Dakota. In addition, the researchers will be working with National Center for Supercomputer Applications on a storm exhibit at the Chicago Museum of Science and Industry. The latter will include interactive tools for exploring simulation data as well as visualizations from supercell/tornado simulations. Three graduate students will be supported and cross institution collaboration will be fostered by the work between two academic institutions.