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

Being different from the scanning radar, the vertical detection radar is used to analyze the micro-physics process in the precipitation cloud and the fusion layer from the vertical structural feature and the evolution 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. Excluding effects of phase changes and particle number concentration changes, the vapor change in the melting 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.