Sensitivity optimization of low coherence Doppler lidar for wind measurement

Air pollution by particulate matters such as PM 2.5 has become a big problem about negative impact on the human body near the ground. Particulate matters activity follows wind flow and have a localized and complex distribution near the ground surface, depending on topography and structures on ground / sea surface. A Doppler Lidar is a useful method for wind measurement because the spatial distribution of wind can be obtained without disturbing the wind field, but monitoring near the ground requires high spatiotemporal resolution of a few meters and seconds. We have developed a Low Coherence Doppler Lidar (LCDL) with a high spatial resolution of 1m. Previous studies had been able to measure dust winds from dust dispersal but lacked the sensitivity to measure the winds themselves. To improve the sensitivity of the Lidar, the system was changed from a bistatic to a coaxial system. Compared to our previous setup, the sensitivity was improved by about 8 dB. Sensitivity was further improved by 10dB by devising the optical system. Calculating the SNR from the wind, it was estimated that the wind measurement would be sufficient within the 20 m measurement range.