Abstract:
Herein, to further study the vertical structure of the northeast cold vortex cloud system precipitation, the microphysical characteristics of three northeast China cold vortex precipitation events in Fuxin since 2020 are analyzed using a Micro rain radar (MRR) and laser disdrometer deployed at the national ground observation station of Fuxin Mongol Autonomous County, Liaoning Province. Results show that the raindrop size distributions (RSDs) measured by the MRR and disdrometer have high consistency in cases dominated by stable precipitation of stratus clouds and that the average RSDs only show high agreement in the medium particle size range (1–2.5 mm) in cases with a higher proportion of convective precipitation. During stratiform precipitation, the smaller ice crystal particles begin to melt faster through the 0°C layer, the small liquid droplets accumulate below the 0°C layer, and the extreme value of the droplet concentration appears. Conversely, the larger ice crystal particles experience a longer melting distance and become larger raindrops. Moreover, the accumulation of small liquid droplets below the 0 C layer further promotes the collection and collision of large droplets, which is conducive to the formation of larger raindrops. Furthermore, an extreme value of the width of RSD appears below the melting layer, manifesting as a “bulge” whose entire lifecycle, from the onset of its formation to decay, occurs within a 2–3 minute timeframe.. Whether the broadening of RSD in the vertical direction can considerably increase rainfall intensity on the ground depends on the water vapor content in the near-surface atmosphere. In the dry spring of western Liaoning, the relative humidity of the atmosphere is low, and the existing of melting layer has no obvious help for broadening the ground RSD. However, in summer, when the water vapor is relatively abundant, the downward movement of the “bulge” to a certain extent leads to the widening of the near-ground RSD and an increase in rain intensity. Compared with the number concentration of rain droplets in other regions, that in western Liaoning is smaller. Still, the average concentrations of stratus and convective precipitation are not considerably different; moreover, the difference in mass-weighted diameter of rain droplets leads to a difference in rain intensity.