Experimental calibration assessment of a MPLNET/Micro-Pulse Lidar system in comparison with EARLINET lidar measurements for aerosol optical properties retrieval.

Simultaneous observations of a polarized Micro-Pulse Lidar (P-MPL) system, currently operative within MPLNET (NASA Micro-Pulse Lidar Network), with two referenced EARLINET (European Aerosol Research Lidar Network) lidars, running at Leipzig site (Germany, 51.4°N 12.4°E, 125 m a.s.l.), were performed during a comprehensive two-month field campaign in summer 2019. A calibration assessment regarding the overlap (OVP) correction of the P-MPL signal profiles and its impact in the retrieval of the optical properties is achieved, describing also the experimental procedure used. The optimal lidar-specific OVP function for correcting the P-MPL measurements is experimentally determined, highlighting that the OVP function as delivered by the P-MPL manufacturer cannot be used. Among the OVP functions examined, the averaged one between those obtained from the comparison of the P-MPL observations with those of the other two referenced lidars seems to be the best proxy at both near- and far-field ranges. In addition, the impact of the OVP function in the accuracy of the retrieved profiles of the total particle backscatter coefficient (PBC) and the particle linear depolarization ratio (PLDR) is examined. First, the volume linear depolarization ratio (VLDR) profile is obtained and compared to the reference lidars, showing it needs to be corrected by a small offset value within a good accuracy. Once P-MPL measurements are optimally OVP-corrected, the PBC profiles (and hence the PLDR ones) can be derived using the Klett-Fernald approach. In addition, an alternative method based on the separation of the total PBC into their aerosol components is presented in order to estimate the total particle extinction coefficient (PEC) profile, and hence the Aerosol Optical Depth, from elastic P-MPL measurements. A dust event as observed at Leipzig in June 2019 is used for illustration. In overall, an 30 adequate OVP function is needed to be determined in a regular basis to calibrate the P-MPL system in order to derive suitable aerosol products. [ABSTRACT FROM AUTHOR]