ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 47 Issue 5 > 2021,47(5):561-572. DOI:10.7519/j.issn.1000-0526.2021.05.005 Prev Next
Study of Recognition Algorithm of Non-Precipitation Echo for Beijing X-Band Radar Based on Dual Polarization Parameter
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Abstract:
In order to improve the quality and application level of X-band dual polarization radar data, based on the dual polarization radar quality control (dpQC) scheme from National Multi-Radar and Multi-Sensor (MRMS) Quantitative Precipitation Estimation (QPE) System, a new quality control scheme (dpXQC) is designed for X-band dual polarization radar data. In this scheme, threshold discrimination of differential reflectivity is integrated and some algorithm parameters of the original scheme are adjusted locally. The main principles of the dpXQC scheme include the threshold distinguishing precipitation echo from non-precipitation echo is adjusted to 0.9 when correlation coefficient (CC) of radar echo is used and those less than 0.9 are judged as non-precipitation echoes based on the statistical data； hail and the non-uniform beam filling region are identified by calculating the radar echo top and the location of the powerful echo area; melting layer is distinguished through the feature of CC around 0℃ height of sounding data; radar echo whose absolute value of differential reflectivity is larger than 5 dB is judged as non-precipitation echoes. The scheme also includes the algorithm of spike filter, continuous check and speckle filter. The dpXQC quality control scheme is used to do the test on the 5 Beijing X-band dual polarization radars, and the identification effect of non-precipitation echo is evaluated. The results show that most non-precipitation echoes can be filtered by the CC threshold. The residual non-precipitation echoes with CC larger than 0.9 including the stripe clutter, 〖JP2〗scattered clutter and the small-area clutter, can be removed by spike filter, continuous check and differential reflectivity threshold discrimination. The precipitation echo with CC less than 0.9 in the hail, the non-uniform beam filling and the melting layer region can be protected from CC filter by dpXQC〖JP〗 scheme; the statistical result reveals that the hit rate of recognition of non-precipitation echoes of the dpXQC scheme is 91.8% while the false alarm rate is 20.8%， so it is better than dpQC scheme. There are two main reasons for the high false alarm rate: one is that some non-uniform beam filling regions far away from the radar are not identified by algorithm because of severe attenuation of X-band radar, and the other is that the location and thickness of melting layer are fixed in every azimuth in algorithm, which does not accord with the actual observation. These cause some precipitation echoes with CC less than 0.9 to be identified as non-precipitation echoes in the unrecognized region. Overall, the non-precipitation echoes can be filtered while most precipitation echoes could be returned so that some professional work about the quantitative application of X-band dual polarization radar can be ensured by the dpXQC quality control algorithm.
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