Applications of Cell-Ratio Constant False-Alarm Rate Method in Coherent Doppler Wind Lidar.

Hao Zhu; Lingbing Bu; Haiyang Gao; Xingyou Huang; Wentao Zhang

A cell-ratio constant false-alarm rate (CR-CFAR) method for detecting the Doppler frequency shift is proposed to improve the accuracy of velocity measured by coherent Doppler wind lidar (CWL) in low signal-to-noise ratio (SNR) environments. The method analyzes the spectrum to solve issues of weak signal submergence in noise encountered in thewidely used periodogrammethod. This characteristic is that the signal region slope is larger than the noise region slope in the frequency spectrum. We combined the ratio and CFAR to propose the CR-CFAR method. The peak area is discriminated from the spectrum using this method. By removing background noise, the peak signal is obtained along with the Doppler shift. To verify the CR-CFAR method, a campaign experiment using both CWL and a commercial Doppler lidar was performed in Hami, China (42°320 N, 94°030 E) during 1-7 June 2016. The results showed that the proposed method significantly improved the reliability of CWL data under low SNR conditions. The height--at which both horizontal wind speed correlativity and horizontal wind direction correlativity exceeded 0.99--increased by 65 m. The relative deviation of the horizontal wind speed at 120 m decreased from 40.37% to 11.04%. We used the CR-CFAR method to analyze continuous data. A greater number of wind field characteristics were obtained during observation compared to those obtained using the common wind field inversion method.

FALSE alarms; DOPPLER effect; LIDAR; SIGNAL processing; RELIABILITY in engineering

Atmosphere, 2016, Vol 7, Issue 12, p165

2073-4433

Academic Journal

10.3390/atmos7120165