Observation and Analysis of Snowband Structure in a Process of Cyclone Frontal Snowfall in Beijing with Ka-band and X-band Polarized Radars

A simultaneous observation method combining a Ka-band polarized radar and an X-band polarized radar, both of which located at the same observation station of the Institute of Atmospheric Physics, Chinese Academy of Sciences, has been designed for the first time and discussed in this paper. The method has been applied to the study of the formation and development of the snowbands during the snowfall process of a frontal cyclone system in Beijing on February 14, 2019, and the lifecycle and vertical structure of the snowbands are analyzed. Results show that the vertical structure of the snowbands has similar layered structures as previously known, however is different from the four-layer structure composed of condensation layer, aggregation layer, riming layer and melting layer of rainbands. The snowbands only contain condensation layer, aggregation layer and riming layer formed from the seeding of the upper layer cloud to the lower layer cloud. Horizontal wind speeds vary from layer to layer, so the three layers of a snowband may not be aligned vertically. Multiple snowbands are continuously generated and developed to maintain the snowfall. Snowflakes are formed continuously in the snowbands until the condensation layer becomes empty, and the cloud is then split from this layer into multi-layers and dissipates from there, respectively. The study has proven that the simultaneous observations by the dual frequency polarized radars is necessary and efficient. It has extended the application capability of the Ka-band and X-band radars for the observation of snowfalls and enriched the understanding of snowbands in frontal cyclone systems.