Modifications to the Roscoe Lidar to Improve Signal-to-Noise and Depolarization Ratios of Clouds

An airborne backscatter lidar with the unique feature of measuring in both the nadir and zenith directions was developed to provide vertical profiles of the troposphere and stratosphere from a high-altitude aircraft platform. The Roscoe lidar measures backscatter at the 355 nm and 1064 nm wavelengths, with the capability of retrieving depolarization ratios at both wavelengths. In 2022 Roscoe was flown on two field campaigns: Stratospheric Aerosol processes, Budget, and Radiative Effects (SABRE) and Asian Summer Monsoon Chemical and CLimate Impact Project (ACCLIP). While Roscoe was able to measure features such as clouds and aerosol layers during ACCLIP and SABRE, the instrument performance was not fully optimized. To improve the signal-to-noise ratio (SNR) and provide more accurate depolarization ratios, modifications to Roscoe’s optical bench and optical alignment were performed. Here, we present an overview of the Roscoe instrument and examples of ice and liquid cloud data from before and after the modifications.