TY - JOUR
T1 - The mechanisms responsible for large near-surface vertical vorticity within simulated supercells and quasi-linear storms
AU - Boyer, Christian H.
AU - Dahl, Johannes M.L.
N1 - Funding Information:
Acknowledgments. The authors thank Dr. George Bryan for providing and maintaining the CM1 source code as well as Drs. Paul Markowski and Matt Parker for numerous beneficial discussions. We also thank Matt Flournoy and two anonymous reviewers for their thoughtful comments that helped clarify and improve the presentation of the manuscript. We also thank the first author’s committee members, Drs. Brian Ancell and Eric Bruning, for helpful comments on improving the research in this study. We also acknowledge the support of the High Performance Computing Center at Texas Tech University. Funding for Johannes M. L. Dahl came from the NSF Grant AGS-1651786.
Publisher Copyright:
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PY - 2020/10
Y1 - 2020/10
N2 - Despite their structural differences, supercells and quasi-linear convective systems (QLCS) are both capable of producing severe weather, including tornadoes. Previous research has highlighted multiple potential mechanisms by which horizontal vorticity may be reoriented into the vertical at low levels, but it is not clear in which situation what mechanism dominates. In this study, we use the CM1 model to simulate three different storm modes, each of which developed relatively large near-surface vertical vorticity. Using forward-integrated parcel trajectories, we analyze vorticity budgets and demonstrate that there seems to be a common mechanism for maintaining the near-surface vortices across storm structures. The parcels do not acquire vertical vorticity until they reach the base of the vortices. The vertical vorticity results from vigorous upward tilting of horizontal vorticity and simultaneous vertical stretching. While the parcels analyzed in our simulations do have a history of descent, they do not acquire appreciable vertical vorticity during their descent. Rather, during the analysis period relatively large horizontal vorticity develops as a result of horizontal stretching, and therefore this vorticity can be effectively tilted into the vertical.
AB - Despite their structural differences, supercells and quasi-linear convective systems (QLCS) are both capable of producing severe weather, including tornadoes. Previous research has highlighted multiple potential mechanisms by which horizontal vorticity may be reoriented into the vertical at low levels, but it is not clear in which situation what mechanism dominates. In this study, we use the CM1 model to simulate three different storm modes, each of which developed relatively large near-surface vertical vorticity. Using forward-integrated parcel trajectories, we analyze vorticity budgets and demonstrate that there seems to be a common mechanism for maintaining the near-surface vortices across storm structures. The parcels do not acquire vertical vorticity until they reach the base of the vortices. The vertical vorticity results from vigorous upward tilting of horizontal vorticity and simultaneous vertical stretching. While the parcels analyzed in our simulations do have a history of descent, they do not acquire appreciable vertical vorticity during their descent. Rather, during the analysis period relatively large horizontal vorticity develops as a result of horizontal stretching, and therefore this vorticity can be effectively tilted into the vertical.
KW - Cloud resolving models
KW - Numerical analysis/modeling
KW - Squall lines
KW - Supercells
KW - Tornadogenesis
KW - Trajectories
UR - http://www.scopus.com/inward/record.url?scp=85093855954&partnerID=8YFLogxK
U2 - 10.1175/MWR-D-20-0082.1
DO - 10.1175/MWR-D-20-0082.1
M3 - Article
AN - SCOPUS:85093855954
VL - 148
SP - 4281
EP - 4297
JO - Monthly Weather Review
JF - Monthly Weather Review
SN - 0027-0644
IS - 10
ER -