Mie lidar observations of lower tropospheric aerosols and clouds

Abstract

Mie lidar system is developed at Laser Science and Technology Centre, Delhi (28.38°N, 77.12°E) by using minimal number of commercially available off-the-shelf components. Neodymium Yttrium Aluminum Garnet (Nd:YAG) laser operating at 1064 nm with variable pulse energies between 25 and 400 mJ with 10 Hz repetition rate and 7 ns pulse duration is used as a transmitter and off-axis CASSEGRAIN telescope with 100 mm diameter as a receiver. Silicon avalanche photodiode (Si-APD) module with built-in preamplifier and front-end optics is used as detector. This system has been developed for the studies of lower tropospheric aerosols and clouds. Some experiments have been conducted using this set up and preliminary results are discussed. The characteristics of backscattered signals for various transmitter pulse energies are also studied. Atmospheric aerosol extinction coefficient values are calculated using Klett lidar inversion algorithm. The extinction coefficient, in general, falls with range in the lower troposphere and the values lie typically in the range 7.5 × 10 −5 m −1 to 1.12 × 10 −4 m −1 in the absence of any cloud whereas this value shoots maximum up to 1.267 × 10 −3 m −1 (peak extinction) in the presence of clouds.