EYE SAFE POLARIZATION DIVERSITY LIDAR FOR AEROSOL STUDIES: CONCEPT DESIGN AND PRELIMINARY APPLICATIONS

The concept design and preliminary applications of a new Eye Safe Polarization Diversity Lidar (ESPDL) instrument are described. The lidar operates with polarization diversity in the laser emission and polarization discrimination in the receiver at 1574 nm for tropospheric aerosol studies in the Arctic atmosphere. This instrument was originally designed to operate in the eye-safe wavelength range with a one-channel receiver and 20 dB linear polarization accuracy in the laser emission, and assembled in a compact optical bench. The instrument was upgraded for polarization diversity laser emission, i.e polarization selectivity better than 30 dB, and for linear polarization reception discrimination, i.e. polarization discrimination better than 50 dB. Geophysical lidar applications under the scope of this instrument with an overall instrumental polarimetric accuracy better than 0.1% focus on the identification of very dilute suspended aerosols in the troposphere, ice in-cloud initiation and aerosol/water interfaces, complex aerosols, sub-visible high altitude clouds and environmental issues and dynamic processes in the Arctic such as ice fog, forest fire, and a multilayered stably stratified Arctic boundary layer. In this article we describe the instrument design concept and the electronic synchronization necessary to achieve the maximum instrumental polarization accuracy. We report a preliminary case study of differential polarization analysis.