C-FMCW雷达对江淮降水云零度层亮带探测研究

Bright Band Analysis in Yangtze-Huaihe Region of Anhui Using Data Detection from C-FMCW Radar

不同于体扫雷达探测降水系统,垂直指向雷达可探测降水云中粒子垂直演变的微物理过程。C波段调频连续波垂直指向雷达（C-FMCW）采用收发分置天线,数据垂直分辨率达15~30 m,时间分辨率达2~3 s,利用其2013年6—8月在安徽定远探测数据对降水云垂直结构特征及亮带中融化微物理过程进行研究。6次降水过程共计46 h中的39.1%数据具有清晰的亮带结构特征,期间降水占地面总降水量的15%;江淮雨季层状云、对流云和混合性降水系统中均出现零度层亮带,层状云中亮带长时间维持,对流降水系统移出后减弱阶段的亮带结构稳定,混合降水系统中的对流扰动加强冲破了亮带结构。以融化层中最大回波强度Z_p所在高度进行融化层的粒子碰并增长和破碎减弱分层分析,上半层融化过程主要表现为碰并增长,下半层则是粒子破碎减弱。剔除了介电常数、下降速度引起的粒子浓度改变影响后,层状云和对流降水后期的回波强度加强表明融化增长程度接近,后者略强,混合降水云的融化增长最强。

Being different from the scanning radar, the vertical detection radar is used to analyze the micro-phys- ics process in the precipitation cloud and the fusion layer from the vertical structural feature and the evolu- tion process of the precipitation cloud. The C-FMCW vertical pointing radar adopts the solid-state system, bistatic antenna technology, and the demodulated signal processing adopts two-dimensional FFT signal processing technology to extract the distance information and the spectrum distribution information in the range bin. The vertical resolution of data is from 15 m to 30 m and the time resolution is from 1 s to 3 s, and the minimum reflectivity at 15 km height is --20 dBZ. Compared with the neighboring CINRAD/SA radars at Bengbu and Hefei, the reflectivity calibration difference is less than 1 dB, and root mean square error is less than 2.02 dB. Using C-FMCW radar detective data from June to August in 2013 at Dingyuan of Anhui, the bright band of the precipitation cloud detection data in 46 h are identified. The cumulative rainfall reaches 340.3 mm, during which 55620 precipitation cloud vertical profiles are obtained. 39.1% of precipitation clouds show clear bright band structural feature and during the occurrence of the bright band the precipitation makes up 15% of the total amount. During the Yangtze-Huaihe rainy season, the bright bands appear in stratiform cloud, convective cloud and the mixed precipitation system. In the stratiform cloud, the bright band is most stable and maintains longer. The bright band appears in the decay stage of the convective precipitation and the melting increase is obviously slower. The aggregation increase is of the strongest in the mixed precipitation system, after which the continuous bight band structure is broken by the strengthened convection distribution. The micro-physics process in the fusion layer is complicated. Ex- cluding effects of phase changes and particle number concentration changes, the vapor change in the melt- ing process is given. The maximum reflectivity in the melting process is used to analyze the layering process. It shows the melting process in the upper layer is mainly absorption growth, while in the lower layer is breakup process.