Validation of a Multilag Estimator on NJU-CPOL and a Hybrid Approach for Improving Polarimetric Radar Data Quality
Validation of a Multilag Estimator on NJU-CPOL and a Hybrid Approach for Improving Polarimetric Radar Data Quality
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NJU-CPOL 上多重滞后估计器的验证和提高偏振雷达数据质量的混合方法，
DOI：
10.3390/rs12010180
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发表时间：
2020-01
期刊：
影响因子：
5
通讯作者：
Huang Hao
中科院分区：
文献类型：
--
作者：
Shao Shiqing;Zhao Kun;Chen Haonan;Chen Jianjun;Huang Hao
针对低信噪比条件下微弱回波信号的估计问题，提出了一种多滞后估计方法，该方法比传统方法具有更好的性能。通过理论分析、模拟雷达数据和C波段极化雷达实测数据，验证了多滞后估计器的性能。在南京大学C波段偏振多普勒天气雷达（NJU-CPOL）2014年“中国强对流观测、预报和分析”（OPACC）外场试验中，对多滞后估计器进行了实现和验证。理论分析和实现结果也进行了比较，包括信号功率、光谱宽度、微分反射率和共极相关系数的估计。结果表明，多滞后估计对信号功率和微分反射率的改善不大，但对谱宽和共极相关系数的改善在谱宽小于2 ms−1时显著，这意味着相关时间尺度较大。然而，在谱宽较大的区域，多重滞后估计存在明显的偏差。基于性能分析，一种混合方法，因此，通过NJU-CPOL观测和检查。该算法根据自相关函数（ACF）的最大可用滞后数，将包括滞后0在内的所有滞后都用于矩估计。实例分析表明，与传统的矩估计方法和多滞后矩估计方法相比，该混合方法可以提高矩估计的精度，特别是对弱天气回波的矩估计。当信噪比降低或传统估计器中噪声功率的偏差增大时，这种改进将是显著的。此外，这种混合方法是很容易实现的业务和非业务雷达。还可以预期，所提出的混合方法将有一个更好的性能，如果应用到S波段极化雷达的两倍，在相同的条件下，与C波段雷达的最大可用滞后。
For the estimation of weak echo with low signal-to-noise ratio (SNR), a multilag estimator is developed, which has better performance than the conventional method. The performance of the multilag estimator is examined by theoretical analysis, simulated radar data and some specific observed data collected by a C-band polarimetric radar in previous research. In this paper, the multilag estimator is implemented and verified for Nanjing University C-band polarimetric Doppler weather radar (NJU-CPOL) during the Observation, Prediction and Analysis of Severe Convection of China (OPACC) field campaign in 2014. The implementation results are also compared with theoretical analysis, including the estimation of signal power, spectrum width, differential reflectivity, and copolar correlation coefficient. The results show that the improvement of the multilag estimator is little for signal power and differential reflectivity, but significant for spectrum width and copolar correlation coefficient when spectrum width is less than 2 ms−1, which implies a large correlation time scale. However, there are obvious biases from the multilag estimator in the regions with large spectrum width. Based on the performance analysis, a hybrid method is thus introduced and examined through NJU-CPOL observations. All lags including lag 0 of autocorrelation function (ACF) are used for moment estimation in this algorithm according to the maximum usable lag number. A case study shows that this hybrid method can improve moment estimation compared to both conventional estimator and multilag estimator, especially for weak weather echoes. The improvement will be significant if SNR decreases or the biases of noise power in the conventional estimator increase. In addition, this hybrid method is easy to implement on both operational and non-operational radars. It is also expected that the proposed hybrid method will have a better performance if applied to S-band polarimetric radars which have twice the maximum useable lags in the same conditions with C-band radars.
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