冷锋期间武汉MST雷达低平流层回波异常现象

武汉MST雷达是中国子午工程建设的两台中高层大气无线电探测雷达之一.该雷达探测频率在VHF频段，雷达回波在低平流层和对流层上部具有角谱特性，可为研究大气动态稳定性提供有效技术手段.本文利用武汉MST雷达2016年4月17日冷锋活动期间及平静天气的角谱实验数据，从雷达回波特性变化、风场空间分布、湍流生成机制以及内重力波影响四个方面分析并解释了MST雷达对流层顶上部区域出现持续异常强回波带的成因.分析结果表明，对流层冷锋的强对流作用诱发内重力波，内重力波向上传播至低平流层后受增强的剪切急流影响发生耗散甚至破碎，激励了长时间跨度的K-H不稳定性，进而导致水平反射层结构发生扰动生成湍流，使得雷达回波结构发生变化. 

Abnormal Echoes in Lower Stratosphere Observed by Wuhan MST Radar during a Cold front Event

Wuhan Mesosphere-Stratosphere-Troposphere (MST) radar is a radio atmosphere detection radar deployed by the Chinese Meridian Project. As the frequency is in VHF band, the echoes are sensitive in all their aspects. Such echo characteristics are much more obvious in the Upper Troposphere and Lower Stratosphere (UTLS), which provides a practical approach to investigate the atmosphere dynamics. Observations of echo characteristic during a cold front are obtained by Wuhan MST radar in mid-latitude in April 2016. The experiment results show that the typical feature of the echo aspect sensitivity is significantly changed compared with that of normal days. Reasons of the echo anomaly are studied by analyzing echo characteristics variations, wind field spatial distributions, turbulence generation mechanisms and Inertia Gravity Waves (IGWs) effects. The result demonstrates that the dissipating (or even breaking) of upward IGWs coming from convection system might feed the long-time persistence of Kelvin-Helmholtz (K-H) instability, which further tilts the horizontal reflection layer and results in the intense turbulence and the echo enhancement.