ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
The Observation Characteristics of Multi-vortexes during Short term rainstorm in Fushun of Liaoning Province Based on Phased Array Radar
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Abstract:
A local short-time rainstorm was affected by a rare precipitation system with 16 mesovortices (referred to as MV) in Fushun of Liaoning province on the night of August 4 2023. The formation mechanism of MVs and the observation characteristics of MVs related to heavy precipitation (RMV) were analyzed by multi-source data such as phased array radar. Liaoning was located on the northern boundary of the 584 dagpm line, influenced by the upper trough and shear line. The abundant water vapor and low lifting condensation level in the Fushun area was the favorable environmental conditions for extreme rainfall. When the heterogeneity of the air masses on both sides of the convergence line increased under the strong vertical wind shear, total 16 MV were detected by phased array radar. The average duration of total MV was 17 minutes, the average thickness and top height was 1.7 km and 3.5 km, respectively. These vortices are low-level and shallow meso-γ-scale vortices. There were up to 49 extreme rainfall stations which the precipitation reached 10 mm within 5 minutes in the areas affected by MVs, with an average distance of only 6.2 km between the heavy precipitation stations and the associated MV. The number of heavy precipitation which caused by the first and fourth MV was 44 stations, accounting for 92% of all heavy precipitation. Compared to other MV, RMV had a longer lifetime and moving distance, with stronger rotation intensity and greater thickness. Two RMV were both generated during the stage where the boundary layer jet was significantly enhanced and the wind vector difference at 0-1 km exceeded 15 m/s. In the early stage of RMV formation, the low-level rotation was the strongest which reaching the standard of moderate intensity mesoscale cyclones, with vigorous storm development above. There was no extreme rainfall near the RMV at this time. Subsequently, the rotational speed of the RMV diminished, and the storm height rapidly decreased. And multiple strong precipitation occurred immediately near the RMV. Additionally, there was a phenomenon of several weaker MV merging with RMV, which was beneficial for the RMV sustainment. In conclusion, the evolution of the position and rotational intensity of RMV is the crucial for warning heavy rainfall.
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