Comparison of radar characteristics of two types of severe convective weather under the background of Northeast cold vortex

At different stages of the development of the cold vortex, different types of severe convective weather occur in different quadrants. In order to deepen understanding of the mechanism of severe convective weather under the influence of the cold vortex system and to accurately identify different types of severe convective weather, this article uses routine data, dual-polarization radar data and ERA5 reanalysis data. The radar characteristics of the severe precipitation (referred to as "8.31" heavy rain) in Liaoning on 31 August 2020 and the large hail (referred to as "9.10" large hail) on 10 September 2021 under the background of the Northeast cold vortex are compared and analyzed, and the development and evolution of different types severe convective weather and the similarities and differences of the microphysical structure are compared. The results are as follows. (1) The "8.31" heavy rain process occurred in the southeastern quadrant during the development stage of the cold vortex. The development of stratification mainly related to strong warm and humid advection at lower levels. The "9.10" large hail process occurred in the southwestern quadrant during the stage of the cold vortex. The northerly flow behind the cold vortex carried strong dry and cold air from high latitudes to the south, and the cold advection at high altitudes was the main factor causing the increase in instability. (2) The development of low-level warm and moist forcing during the strong precipitation process corresponded to the development of radar reflectivity Z in the vertical direction and changed in the height of the Z_dr column. The enhancement of precipitation accompanied by significant low correlation coefficient (CC) gradient zones and large radial velocity zones as low-level inflow characteristics. Before the production of large hail, the strong storm top first experiences strong divergence, which together with upward motion (radial velocity column development) and-level convergence (radial velocity convergence), interacted with strong vertical wind shear to help maintain and strengthen the strong storm. (3) The most severe weather phenomena in the two types of severe convective weather have a good correspondence with the weak echo region, Z-pillar and Z_dr column, mid-level radial convergence, velocity convergence region, Z_dr ring and CC valley, and these key information will have a good indication significance in the short-time forecast and early warning.