The WALI (Weather and Aerosol LIdar) system is a compact and transportable lidar nominally emitting ~100 mJ at 354.7 nm. It is a seasoned mobile system which samples the troposphere for aerosol, water vapor and temperature retrievals. It is designed to fulfill eye-safety standards (EN 60825-1). The receiver is composed of 2 distinct detection modules using small collector telescopes of 15 cm in diameter. The total number of detection channels is six: two cross-polarized channels, Raman elastic channels at ~387 and ~407 nm for dinitrogen and water vapor, and two rotational Raman channels combining the Raman lines of both dinitrogen and dioxygen close to the Cabannes elastic line centered at 354.7 nm. Using short focal length telescopes ensures a low altitude overlap for the lidar beams and increases the overall stability, transmittance and compactness of the instrument. The wide field-of-view (FOV) ~2.3 mrad allows a full-overlap of the transmission and reception paths beyond ~ 200‑300 m. A recent study of Totems et al. (2021) describes in details the instrument along the sources of bias for Raman measurements, and processes for mitigating their impact.
Chazette, P., Marnas, F., and Totems, J. (2014), The mobile Water vapor Aerosol Raman LIdar and its implication in the framework of the HyMeX and ChArMEx programs: application to a dust transport process, Atmos. Meas. Tech., 7, 1629-1647, doi:10.5194/amt-7-1629-2014.
Chazette, P., Marnas, F., Totems, J., and Shang, X.(2014), Comparison of IASI water vapor retrieval with H2O-Raman lidar in the framework of the Mediterranean HyMeX and ChArMEx programs, Atmos. Chem. Phys., 14, 9583-9596, doi:10.5194/acp-14-9583-2014.
Totems, J. and Chazette, P.: Calibration of a water vapour Raman lidar with a kite-based humidity sensor, Atmos. Meas. Tech., 9, 1083-1094, doi:10.5194/amt-9-1083-2016, 2016.
Totems, J., Chazette, P., & Raut, J. (2019). Accuracy of current Arctic springtime water vapour estimates, assessed by Raman lidar. Quarterly Journal of the Royal Meteorological Society, 145(720), 1234–1249.https//doi.org/10.1002/qj.3492.
Totems, J., Chazette, P., and Baron, A.: Mitigation of bias sources for atmospheric temperature and humidity in the mobile Raman Weather and Aerosol Lidar (WALI), Atmos. Meas. Tech., 14, 7525–7544, https://doi.org/10.5194/amt-14-7525-2021, 2021.