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Abstract
The development of vertical vorticity under adiabatic condition is investigated by virtue of the view of
potential vorticity and potential temperature (PV–θ) and from a Lagrangian perspective. A new concept
of generalized slantwise vorticity development (GSVD) is introduced for adiabatic condition. The GSVD
is a coordinate independent framework of vorticity development (VD), which includes slantwise vorticity
development (SVD) when a particle is sliding down the concave slope or up the convex slope of a sharply
tilting isentropic surface under stable or unstable condition. The SVD is a special VD for studying the
severe weather systems with rapid development of vertical vorticity. In addition, the GSVD clarifies VD
and SVD. The criteria for VD and SVD demonstrate that the demand for SVD is much more restricted
than the demand for VD. When an air parcel is moving down the concave slope or up the convex slope of
a sharply tilting isentropic surface in a stable stratified atmosphere with its stability decreasing, or in an
unstable atmosphere with its stability increasing, i.e., its stability θz approaches zero, its vertical vorticity
can develop rapidly if its CD is decreasing.
The theoretical results are employed to analyze a Tibetan Plateau (TP) vortex (TPV), which appeared
over the TP, then slid down and moved eastward in late July 2008, resulting in heavy rainfall in Sichuan
Province and along the middle and lower reaches of the Yangtze River. The change of PV2 contributed to
the intensification of the TPV from 0000 to 0600 UTC 22 July 2008 when it slid upward on the upslope of
the northeastern edge of the Sichuan basin, since the changes in both horizontal vorticity ηs and baroclinity
θs have positive effects on the development of vertical vorticity. At 0600 UTC 22 July 2008, the criterion
for SVD at 300 K isentropic surface is satisfied, meaning that SVD occurred and contributed significantly
to the development of vertical vorticity. The appearance of the stronger signals concerning the VD and
SVD surrounding the vortex indicates that the GSVD concept can serve as a useful tool for diagnosing the
development of weather systems.
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Citation
WU Guoxiong, ZHENG Yongjun, LIU Yimin. 2013: Dynamical and Thermal Problems in Vortex Developmentand Movement. Part II: Generalized SlantwiseVorticity Development. Journal of Meteorological Research, 27(1): 15-25. DOI: 10.1007/s13351-013-0102-2
WU Guoxiong, ZHENG Yongjun, LIU Yimin. 2013: Dynamical and Thermal Problems in Vortex Developmentand Movement. Part II: Generalized SlantwiseVorticity Development. Journal of Meteorological Research, 27(1): 15-25. DOI: 10.1007/s13351-013-0102-2
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WU Guoxiong, ZHENG Yongjun, LIU Yimin. 2013: Dynamical and Thermal Problems in Vortex Developmentand Movement. Part II: Generalized SlantwiseVorticity Development. Journal of Meteorological Research, 27(1): 15-25. DOI: 10.1007/s13351-013-0102-2
WU Guoxiong, ZHENG Yongjun, LIU Yimin. 2013: Dynamical and Thermal Problems in Vortex Developmentand Movement. Part II: Generalized SlantwiseVorticity Development. Journal of Meteorological Research, 27(1): 15-25. DOI: 10.1007/s13351-013-0102-2
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