Abstract:
Herein, a comparative analysis was conducted on the structural characteristics of high-impact eastward-moving Qinghai–Tibet Plateau vortices (TPVs) with quasi-straight long paths (QSLTPVs) and quasi-straight short paths (QSSTPVs) by adopting a dynamic composite method of the TPV in the moving accompanying the TPV. The analysis considered the warm season months from May to September, spanning from 1998 to 2018. To conduct this study, various data sources, including global analysis data obtained from NCEP/NCAR, atmospheric observational data, and the TPV and shear line yearbooks. The relationship between the intensity and structure of QSLTPVs and QSSTPVs was studied, revealing that their evolution is determined to some extent by the structure of the low vortex itself. The key findings of this analysis are as follows: (1) Both QSLTPVs and QSSTPVs exhibit similar structural characteristics. Initially, they form as shallow weather systems and evolve into deeper weather systems upon exiting the Tibetan Plateau, which is a trend consistent with that of the vorticity of low vortices in different activity stages. (2) The structural differences between QSLTPVs and QSSTPVs become apparent during their strengthening stage. QSLTPVs exhibit a thicker positive vorticity column and a stronger ascending motion column compared with those of QSSTPVs. Furthermore, the positive vorticity column of QSLTPVs tilts northward as the height ascending, exhibiting smaller vorticity in the upper layer and larger vorticity in the lower layer. Meanwhile, the positive vorticity column of QSSTPVs display a symmetrical distribution and a vertical vorticity distribution opposite to that of QSLTPVs. In addition, the center of the south wind associated with QSLTPVs is positioned more easterly and the confluence position of easterly and westerly winds is more southerly and stronger compared to the case of QSSTPVs. After departing from the Tibetan Plateau, the center of positive vorticity advection overlying the vortex area of QSLTPVs is lower, the intensity of the advection is strengthened, and the advection lasts longer, deviating to the east of QSLTPVs; meanwhile, QSSTPVs exhibit the opposite pattern. (3)The varying intensities of low vortices during the evolution of QSLTPVs and QSSTPVs are underpinned by the positive vorticity advection of the input vortex regions. The structural differences in the strengthening stage reflect that QSLTPVs incorporate a vertical transport mechanism that increases vorticity and a dynamic mechanism that enhances the forced ascending motion of positive vorticity advection, thereby facilitating the strengthening of the TPVs.