Microphysical Processes of a Cold Vortex during Its Movement to the East: A Case Study

• Main Authors: Yanwei Li, Weiwei Wang, Xin Qin, Gerrit de Leeuw
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Atmosphere
• Subjects: cold vortex; microphysical process; precipitation; cold cloud process
• Online Access: https://www.mdpi.com/2073-4433/11/10/1083

A cold vortex is an important weather system that can cause low temperatures and large amounts of rainfall. Many scientific studies have focused on the climatological features of the cold vortex along with its formation, maintenance, structure, circulation features and precipitation distribution from a synoptic perspective. However, not many studies have been conducted related to the microphysical processes in a cold vortex. In this paper, a model study is presented on the microphysical features in a cloud system associated with a cold vortex system which lasted for four days. The system formed, strengthened, split into two and dissipated while it moved towards the east and brought extensive precipitation to the influenced area. The type and amount of precipitation were not evenly distributed: liquid precipitation covered the whole area influenced by the cloud system, while solid precipitation mainly covered high latitudes north of 48° N. In this case, the cloud system was very cold and the 0 °C; level was very low, with the result that the microphysical features were dominated by cold cloud processes. The mixing ratio of liquid particles was very small, and liquid particles only covered limited areas in the clouds. Due to the low temperature, there were insufficient cloud droplets throughout the whole system for the efficient production of rain droplets by coalescence. The snow mixing ratio was largest, and ice and snow covered the whole cloud area, with very little graupel, which occurred in only a small area. The distribution of the solid particles was influenced by their growth through aggregation, the Bergeron process or accretion, resulting in many snow particles. There were insufficient liquid particles to support the formation of very large particles such as graupel. Liquid precipitation was primarily caused by the melting of snow particles precipitating out of the clouds; solid precipitation was also primarily caused by snow particles that did not melt, along with some graupel.