不同波段垂直指向雷达功率谱密度对比

Comparisons of Doppler Spectral Density Data by Different Bands Pointing Vertically Radars

衰减对回波的影响是雷达探测中的一项重要课题,常用订正方法还有很大提升空间。由于垂直指向雷达观测的功率谱数据包含了非常丰富的微物理及动力信息,该文尝试在功率谱层面对衰减影响机理进行深入讨论,以期改进衰减订正方法。对2014 2016年广东阳江和广东龙门获取的Ka波段毫米波雷达、C波段调频连续波雷达、Ku波段微雨雷达功率谱数据进行对比表明:3部雷达功率谱谱型基本一致,具有一定可靠性。米散射效应反映在功率谱上即经过某一速度后回波强度谱密度的陡降,当降水下落末速度达临界速度时,会对衰减量的计算造成影响。雷达波长越短,受衰减影响越大,衰减对功率谱的影响表现为谱的整体下移,最终导致回波强度小于真值。对于对流云降水,单纯使用经验订正公式获得的结果可能与真实值相差很大,此时需要考虑降水粒子谱分布,在功率谱层面上对订正进一步改善。

The attenuation of the radar echo has always been a difficult problem in radar detections. Results cor- rected by the common methods have some differences with the real detecting value. Due to the richness of the micro physical and dynamic information by the power spectrum data of vertical detecting radars, the mechanism of attenuation could be investigated in the power spectrum layer. And then, a direction of the improvement of attenuation correction could be found by power spectrum data. Comparative research is carried out using the power spectrum data by Ka-band millimeter-wave radar, C-band frequency-modulated continuous-wave radar and Ku-band micro rain radar at Yangjiang of Guang- dong during May--June in 2014 and Longmen of Guangdong during April--May in 2016. The power spec- trum shapes by three radars are almost consistent, especially for the peak velocity and the first atmospheric signal, indicating data of three radars are reliable. In the detection of big particle size precipitation, the ra- dar echo is affected by Mie scattering effects, especially shorter wavelength echoes. The reflect of Mie scattering effects on the power spectrum is a rapid decline of echo intensity during a speed point, which shrink the tail end of the spectrum, reduce signal spectrum width and affect the intensity value. The per- formance of power spectrum is the overall down of spectrum, and it leads to underestimation. In convec- tive cloud precipitation detections, results calculated by the normal empirical formula may have difference with real value. Spectrum distribution could be taken into account in such condition, and the correction methods should be improved by the power spectrum density layer. Finally, the study of the attenuation correction, especially the study in the strong precipitation process, the power spectrum data could be used. But the question how the attenuation effect the power spectrum, the study just offers a direction. It still needs to explore in the quantitative research.