Mid- and Low-Altitude Raman Lidar to Simultaneously Measure Nighttime Water Vapor and All-Day Temperature

Conventional Raman lidar is constrained by the low signal of Raman backscattering, rendering it incapable of measuring the atmospheric parameters in high-altitude regions. This paper presents a powerful Raman lidar that employs a multi-receiver system, enabling simultaneous measurements of optical properties of aerosols, atmospheric temperature, and water vapor. Based on the single-line-extracted pure rotational Raman scattering, the system can make temperature measurements from 1 up to 40 km at night and 20 km during the day by utilizing a high-precision Fabry-Perot Interferometer. The water vapor channel detects the vibrational Raman scattering of water vapor and performs water vapor mixing ratio (WVMR) measurements from 0.3 to 5 km. The measurement comparisons between the lidar and the microwave radiometer and radiosonde demonstrate the capability of the lidar system. In the case of 1-hr lidar measurement data integration, the statistical errors of the temperature are within 1 K under 300 m resolution, while the WVMR errors are within 0.5 g/kg under 30 m resolution. This indicates that the lidar data inversion results are effective. Moreover, the 24-hr continuous observations demonstrate the performance of the lidar system during the daytime, also further substantiating the stability of the Raman lidar system. The high-resolution atmospheric temperature and water vapor measurements reveal the negative correlations of their perturbations in the case observation.