Assessment of a three-frequency alternate pulse Doppler wind lidar

Abstract

Incoherent Doppler wind lidar measures the wind by detecting the frequency shift of the laser backscattering from aerosol and atmosphere molecules. The wind measurement sensitivity of edge detection technology like iodine vapor filter depends on the aerosol load of probe volume. The current Direct detect wind lidar system has to obtain the measurement sensitivity from the independent measurement or prior atmosphere aerosol data before accurate wind retrieval. Otherwise, the variation of aerosol mixing ratio would introduce great uncertainty in the wind speed measurement, which is unacceptable on airborne and space-borne Doppler lidar. This paper proposes a new method to achieve real-time wind speed calibration by three adjacent frequency laser pulses alternately transmitted. Three laser pulses are frequency locked to the middle and two wings of the iodine filter absorption line. Because the frequency of triple pulses is changing rather fast, it can be approximately regarded as a synchronous measurement of both aerosol mixing ratio and wind speed. By this way, we can not only ensure the wind measure accuracy, but also achieve the reliable wind field measurement on a mobile platform.