Abstract:
At different stages of the development of the northeast cold vortex, different types of severe convective weather occur in different quadrants. Continuously deepening the understanding of the formation mechanism of severe convective weather under the influence of cold vortex systems can help accurately identify different types of severe convective weather. Under the background of the Northeast Cold Vortex, Liaoning Province experienced a heavy precipitation event on August 31, 2020 (referred to as "8.31" heavy rain event) and a large hail event on September 10, 2021 (referred to as the "9.10" large hail event). Using conventional observation data, dual polarization radar data, and ERA5 reanalysis data, the radar characteristics of these two heavy convective events were compared and analyzed, with a focus on the similarities and differences in the development and microphysical structure of the two types of heavy convective weather storms. 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
Zdr 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
Zdr column, mid-level radial convergence, velocity convergence region,
Zdr ring and CC valley, and these key information will have a good indication significance in the short-time forecast and early warning.