The effects of thermodynamic variability on low-level baroclinity and vorticity within numerically simulated supercell thunderstorms
Jeffrey Beck, Texas Tech Univ., Lubbock, TX; and C. C. Weiss
Past idealized supercell thunderstorm modeling has been used to understand the fundamental dynamics of mesocyclogenesis and tornadogenesis with promising results. However, a very similar initialized sounding has been used for many of these simulations. Observations have shown that this specific atmospheric profile (Weisman and Klemp 1984) represents a small portion of the atmospheric domain in which supercells can exist. In addition, observational research of supercells has shown a variety of low-level structural and evolutionary differences, including variability in low level boundaries, horizontal vorticity, and origins for trajectories entering the low-level mesocyclone.
To better understand low-level variability in supercells, it may be important to assess changes in the larger scale environment, which have already been implicated in broader supercell development (Weisman and Klemp 1982). Therefore, the impact that thermodynamic changes to the environment have on the evolution and structure of low-level baroclinity and horizontal/vertical vorticity within the storm are the focus of this work. Specifically, the Weather Research and Forecasting (WRF) model was used to study idealized supercells with a variety of different initial conditions.
The data show that variations in environmental profile moisture, lapse rate, and microphysics have a significant impact on the development, evolution, and strength (low-level vertical vorticity) of the storm. For example, the interaction of environmental and storm-processed air provides one mechanism for the generation of baroclinity. However, in some simulations, descent of air parcels from varying heights within close proximity to each other provides an alternate generation mechanism. Frontogenesis, trajectory, and vorticity tendency analyses were also conducted. These findings will help lead to a better understanding of how environmental parameters affect small-scale low-level phenomena inside the storm.
Extended Abstract (1.3M)
Session 15, Numerical Modeling: Storm and Environment
Thursday, 30 October 2008, 10:30 AM-12:00 PM, North & Center Ballroom
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