降雪回波的双偏振雷达云相态垂直特征分析

双偏振多普勒天气雷达为探测降雪回波提供了丰富信息,其中距离高度显示RHI(range height indicator)垂直特征有助于识别降水云体相态分布的精细结构。以2018年1月3～5日南京信息工程大学C波段双偏振雷达RHI扫描的暴雪回波为例,结合探空资料进行物理量诊断,研究暴雪回波偏振参量和非偏振参量的相态分布垂直特征及其与大气风温湿结构的关系。结果表明:暴雪回波中,雷达高带或淞附效应存在于6 km高度附近,温度在-12～-15℃,含有湿雪和冰晶粒子;2 km高度附近的差分反射率因子强回波带为增温增湿的层云,层云之上的热力不稳定易促进对流抬升,揭示了冬季降雪具有高架对流的特点。研究结果有益于深入认识降雪在垂直方向上的精细结构及云微物理机制,提高降雪的预测能力。

Vertical Characteristic Analysis of Cloud Phase of Dual-Polarization Radar with Snowfall Echo

Dual-polarization doppler weather radar provides a wealth of information in detecting snowfall. The vertical characteristics of RHI (range height indicator) help to identify the detailed structure of the phase distribution of precipitation clouds. In this paper, taking the snowstorm echo of the RHI scanned by the C band dual-polarization radar from January 3 to 5, 2018 in Nanjing University of Information Science and Technology as a case, combined with sounding data for physical quantity diagnosis to study the vertical characteristics of the phase distribution of polarization parameters and non-polarization parameters of snowstorm echo and their relationship with atmospheric wind, temperature and humidity structure. The results show that the radar high band or rime attached effect exists near the height of 6 km in the snowstorm echo, the temperature is between -12 °C and -15 °C, the radar high band contains wet snow and ice crystals; strong echo band of the differential reflectivity factor near 2 km height is a stratus with warming and humidifying. The thermal instability above the stratus tends to promote convective uplift, revealing the characteristics of elevated convection in winter snowfall. The results are helpful for understanding the detailed structure of snowfall in the vertical direction, and the cloud microphysical mechanism to improve the prediction ability of snowfall.