Analysis of the observational characteristics of two types meso-γ-scale vortices in the same linear storm under the background of Northeast China Cold Vortex

During the early morning of 24 July 2024, a mesocyclone and a mesovortex co-occurred within a linear storm produce short-duration heavy rainfall and thunderstorm gales in Liaoning Province. This study investigates the observed evolution and environmental conditions of this event, as well as the kinematic and microphysical characteristics of different types of meso-γ-scale vortices by analyzing sounding observations, automatic weather station data, dual-polarization radar, and ERA5 reanalysis data. Ultimately, a physical model for short-duration heavy rainfall and thunderstorm gales associated with these meso-γ-scale vortices within the storm is proposed. The result are as follows. (1) Liaoning Province was located at the southern periphery of the Northeast China Cold Vortex (NCCV), characterized by convective available potential energy exceeding 1 000 J·kg⁻¹ and strong vertical wind shear. During the night of 23 July, a linear storm formed and moved southeastward, with a mesocyclone developing on its right flank and a low-level convergence zone present at its leading edge. (2) The linear storm initially merged with a cell to its left-front at low levels, triggering the genesis of a shallow low-level mesovortex (MV) along the convergence zone. At this stage, regions with high differential reflectivity (Z_dr) and specific differential phase (K_dp) existed near both the mesocyclone and the MV. The high-value areas of Z_dr and K_dp were in the lower layer of the storm and not coincident, there were fewer strong convective weather at this time. (3) The linear storm and the frontal storm merged again over the MV, and the MV showed characteristics of bottom-up development and increased rotational speed. MV formered larger particles through the ice phase process, while increasing the mechanism of rainwater transport within the storm. There was a phenomenon of increasing and approaching high values of Z_dr and K_dp between MV and the convergence zone. Consequently, there was an increase in the number of stations reporting severe convection within 5-min intervals. (4) During heavy rainfall, the column-averaged reflectivity and mean K_dp were higher than those during thunderstorm gales, while Z_dr was relatively lower. In contrast, during thunderstorm gale events, the Z_dr at 6 km within the cold cloud layer was 0.3 dB higher than that during heavy rainfall, and these polarimetric variables exhibited a more pronounced decrease with decreasing altitude from 3.5 km down to the surface. The findings of this study can provide reference for improving the early warning capabilities for severe convective weather associated with meso-γ-scale vortices under the background of NCCV.