Numerical Simulations of Supercell Storms Employing the Thin Boundary Layer Equations.
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| Title: | Numerical Simulations of Supercell Storms Employing the Thin Boundary Layer Equations. |
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| Authors: | Allen, Kiley Q.1 (AUTHOR), Pan, Ying1 (AUTHOR), Markowski, Paul M.1 (AUTHOR) pmarkowski@psu.edu |
| Source: | Journal of the Atmospheric Sciences. Feb2026, Vol. 83 Issue 2, p237-253. 17p. |
| Subjects: | Large eddy simulation models, Boundary layer equations, Vortex motion, Computer simulation, Turbulent boundary layer, Thunderstorms |
| Abstract: | Three relatively high-resolution (75-m horizontal grid spacing), large-eddy simulation (LES) ensembles of tornadic supercell storms are used to investigate the effect of a more realistic treatment of the lower boundary condition on supercell storm simulations. These ensembles vary only in the parameterization of near-surface turbulence: one ensemble uses the semislip scheme, whereas the other two employ versions of the "thin boundary layer equations" (TBLE) approach. Each simulated storm is a long-lived supercell, with an intense mesocyclone and at least one tornado-like vortex (TLV). The primary differences observed across the ensembles are (i) the amplitude of near-surface turbulent eddies in the environmental boundary layer and (ii) the intensity of the TLVs, with both TBLE schemes resulting in stronger turbulent eddies in the environment and stronger TLVs within the simulated storms. Although substantial variations in precipitation distribution and cold pool strength are also found among the simulations, the differences in these larger-scale storm attributes from one ensemble to another are not statistically significant. Significance Statement: The assumptions implicit in the semislip boundary condition, which is the lower boundary condition most commonly used in convective storm simulations that include surface drag, are problematic. An alternative approach to modeling the effects of the lower boundary, borrowed from the engineering large-eddy simulation community, is adopted for numerical simulations of supercell storms. The approach at least avoids some of the thorny assumptions inherent in the semislip condition. Though it is not yet possible to know which storm simulations are ultimately the "best," an awareness of their sensitivities to the handling of the unresolved/underresolved flow in the near-surface layer is an important first step toward improving their realism. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Three relatively high-resolution (75-m horizontal grid spacing), large-eddy simulation (LES) ensembles of tornadic supercell storms are used to investigate the effect of a more realistic treatment of the lower boundary condition on supercell storm simulations. These ensembles vary only in the parameterization of near-surface turbulence: one ensemble uses the semislip scheme, whereas the other two employ versions of the "thin boundary layer equations" (TBLE) approach. Each simulated storm is a long-lived supercell, with an intense mesocyclone and at least one tornado-like vortex (TLV). The primary differences observed across the ensembles are (i) the amplitude of near-surface turbulent eddies in the environmental boundary layer and (ii) the intensity of the TLVs, with both TBLE schemes resulting in stronger turbulent eddies in the environment and stronger TLVs within the simulated storms. Although substantial variations in precipitation distribution and cold pool strength are also found among the simulations, the differences in these larger-scale storm attributes from one ensemble to another are not statistically significant. Significance Statement: The assumptions implicit in the semislip boundary condition, which is the lower boundary condition most commonly used in convective storm simulations that include surface drag, are problematic. An alternative approach to modeling the effects of the lower boundary, borrowed from the engineering large-eddy simulation community, is adopted for numerical simulations of supercell storms. The approach at least avoids some of the thorny assumptions inherent in the semislip condition. Though it is not yet possible to know which storm simulations are ultimately the "best," an awareness of their sensitivities to the handling of the unresolved/underresolved flow in the near-surface layer is an important first step toward improving their realism. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00224928 |
| DOI: | 10.1175/JAS-D-25-0101.1 |
