Initial assessment of lidar signal and the first result of a Raman lidar installed at a high altitude station in India

Abstract

Abstract: The lidar backscattered signal can be simultaneously received in both analog (in millivolts) and photon counting (PC in MHz) modes to achieve the better signal for both low and high altitudes. One way to get a better signal is by gluing both signals into a single profile and this single profile contains the high linearity and high sensitivity of the analog and PC signals respectively. In this paper, the experimentally obtained lidar backscattered signal from a high altitude station in Himachal Pradesh region of India is used for gluing and various steps involved in the gluing technique are described. Glued Signal has been used to verify the correct alignment of the lidar system and to obtain the vertical distribution of optical profiles of aerosol and clouds such as backscatter coefficient, extinction coefficient, linear depolarization ratio, optical depth from lidar and Microtop Sunphotometer, Planetary boundary layer (PBL) height etc. The results reveal that the most of the aerosols are confined in the lower troposphere within 4 km and above 4 km, the backscattered signal was mainly due to the molecules during the observed period. The mean lidar ratio (LR) values werefound to be 38.5 ± 14.5sr and 35.75 ± 14.75sr in the month of June and November 2016 respectively suggesting presence of urban aerosols and the observed depolarization ratio values suggest the dominance of spherical particles. The average PBL height was observed as 738 ± 423m and 542 ± 273m in the month of June and November 2016.