摘要:本文设计了中国科学院大气物理研究所位于同一观测站内的一部单发双收Ka波段双偏振雷达和一部双发双收X波段双偏振雷达高效结合观测的方法，并首次将Ka和X波段双偏振雷达结合应用在降雪过程的观测中，对2019年2月14日锋面气旋系统在北京地区降雪过程中雪带的形成、发展、消亡过程的宏微观结构进行了分析。结果表明，雪带的垂直结构符合以往对层状云垂直分层的物理认识，类似但不同于雨带由凝结增长层、丛集层、淞附层、融化层组成的四层结构，雪带只包含由上层“播种”至下层的冰晶形成的凝结增长层、丛集层和淞附层三层。由于各层水平风速不同，雪带的三层结构并非垂直排列。多个雪带不断生成发展维持降雪，直至冰晶凝结生长层变空，云从冰晶凝结生长层分裂为多层云后各自消散。证明了Ka和X波段双偏振雷达结合的必要性和高效性，丰富了对锋面气旋系统雪带的认识，补充了Ka波段和X波段雷达对降雪的观测研究。
关键词:Ka和X波段双偏振雷达/
同步观测/
锋面气旋系统/
雪带结构
Abstract: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.
Key words:Ka- and X-band polarized radars/
Simultaneous observation/
Cyclone frontal system/
Snowband structure
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